[xiph-commits] r11041 - trunk/vorbis/doc
giles at svn.xiph.org
giles at svn.xiph.org
Mon Mar 20 12:20:38 PST 2006
Author: giles
Date: 2006-03-20 12:20:37 -0800 (Mon, 20 Mar 2006)
New Revision: 11041
Removed:
trunk/vorbis/doc/draft-ietf-avt-vorbis-rtp-00.txt
trunk/vorbis/doc/draft-ietf-avt-vorbis-rtp-00.xml
trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-03.txt
trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-04.xml
trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-05.txt
trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-05.xml
Modified:
trunk/vorbis/doc/Makefile.am
Log:
Remove the obsolete vorbis rtp drafts.
Modified: trunk/vorbis/doc/Makefile.am
===================================================================
--- trunk/vorbis/doc/Makefile.am 2006-03-20 20:15:52 UTC (rev 11040)
+++ trunk/vorbis/doc/Makefile.am 2006-03-20 20:20:37 UTC (rev 11041)
@@ -6,7 +6,8 @@
### all of the static docs, commited to SVN and included as is
static_docs = \
- draft-kerr-avt-vorbis-rtp-03.txt \
+ draft-ieft-avt-rtp-vorbis-00.xml \
+ draft-ieft-avt-rtp-vorbis-00.txt \
eightphase.png \
evenlsp.png \
floor1_inverse_dB_table.html \
@@ -100,7 +101,7 @@
@mkdir -p $(BUILDDIR)
@for file in $(doc_sources); do cp $(srcdir)/$$file $(BUILDDIR); done
# translate the draft rtp.txt to .xml in the BUILDDIR
-$(BUILDDIR)/draft-rtp.xml: draft-kerr-avt-vorbis-rtp-03.txt
+$(BUILDDIR)/draft-rtp.xml: draft-ietf-avt-rtp-vorbis-00.txt
cat $< | sed 's/ //g' > $@
# cat $< | sed 's/ //g' | sed 's/</\</g' | sed 's/>/\>/g' > $@
Deleted: trunk/vorbis/doc/draft-ietf-avt-vorbis-rtp-00.txt
===================================================================
--- trunk/vorbis/doc/draft-ietf-avt-vorbis-rtp-00.txt 2006-03-20 20:15:52 UTC (rev 11040)
+++ trunk/vorbis/doc/draft-ietf-avt-vorbis-rtp-00.txt 2006-03-20 20:20:37 UTC (rev 11041)
@@ -1,1458 +0,0 @@
-
-
-
-
-AVT Working Group L. Barbato
-Internet-Draft Xiph.Org
-Expires: August 24, 2006 February 20, 2006
-
-
- draft-ietf-avt-vorbis-rtp-00
- RTP Payload Format for Vorbis Encoded Audio
-
-Status of this Memo
-
- By submitting this Internet-Draft, each author represents that any
- applicable patent or other IPR claims of which he or she is aware
- have been or will be disclosed, and any of which he or she becomes
- aware will be disclosed, in accordance with Section 6 of BCP 79.
-
- Internet-Drafts are working documents of the Internet Engineering
- Task Force (IETF), its areas, and its working groups. Note that
- other groups may also distribute working documents as Internet-
- Drafts.
-
- Internet-Drafts are draft documents valid for a maximum of six months
- and may be updated, replaced, or obsoleted by other documents at any
- time. It is inappropriate to use Internet-Drafts as reference
- material or to cite them other than as "work in progress."
-
- The list of current Internet-Drafts can be accessed at
- http://www.ietf.org/ietf/1id-abstracts.txt.
-
- The list of Internet-Draft Shadow Directories can be accessed at
- http://www.ietf.org/shadow.html.
-
- This Internet-Draft will expire on August 24, 2006.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (2006).
-
-Abstract
-
- This document describes an RTP payload format for transporting Vorbis
- encoded audio. It details the RTP encapsulation mechanism for raw
- Vorbis data and details the delivery mechanisms for the decoder
- probability model, referred to as a codebook and other setup
- information.
-
- Also included within the document are the necessary details for the
- use of Vorbis with MIME and Session Description Protocol (SDP).
-
-
-
-
-Barbato Expires August 24, 2006 [Page 1]
-
-Internet-Draft draft-ietf-avt-vorbis-rtp-00 February 2006
-
-
-Editors Note
-
- All references to RFC XXXX are to be replaced by references to the
- RFC number of this memo, when published.
-
-
-Table of Contents
-
- 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
- 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
- 2. Payload Format . . . . . . . . . . . . . . . . . . . . . . . . 3
- 2.1. RTP Header . . . . . . . . . . . . . . . . . . . . . . . . 3
- 2.2. Payload Header . . . . . . . . . . . . . . . . . . . . . . 5
- 2.3. Payload Data . . . . . . . . . . . . . . . . . . . . . . . 6
- 2.4. Example RTP Packet . . . . . . . . . . . . . . . . . . . . 7
- 3. Configuration Headers . . . . . . . . . . . . . . . . . . . . 8
- 3.1. In-band Header Transmission . . . . . . . . . . . . . . . 9
- 3.1.1. Packed Configuration . . . . . . . . . . . . . . . . . 9
- 3.2. Out of Band Transmission . . . . . . . . . . . . . . . . . 10
- 3.2.1. Packed Headers . . . . . . . . . . . . . . . . . . . . 10
- 3.3. Loss of Configuration Headers . . . . . . . . . . . . . . 13
- 4. Comment Headers . . . . . . . . . . . . . . . . . . . . . . . 13
- 5. Frame Packetization . . . . . . . . . . . . . . . . . . . . . 14
- 5.1. Example Fragmented Vorbis Packet . . . . . . . . . . . . . 15
- 5.2. Packet Loss . . . . . . . . . . . . . . . . . . . . . . . 17
- 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
- 6.1. Mapping MIME Parameters into SDP . . . . . . . . . . . . . 19
- 6.1.1. SDP Example . . . . . . . . . . . . . . . . . . . . . 20
- 6.2. Usage with the SDP Offer/Answer Model . . . . . . . . . . 21
- 7. Congestion Control . . . . . . . . . . . . . . . . . . . . . . 21
- 8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
- 8.1. Stream Radio . . . . . . . . . . . . . . . . . . . . . . . 21
- 9. Security Considerations . . . . . . . . . . . . . . . . . . . 22
- 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22
- 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
- 11.1. Normative References . . . . . . . . . . . . . . . . . . . 23
- 11.2. Informative References . . . . . . . . . . . . . . . . . . 23
- Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 25
- Intellectual Property and Copyright Statements . . . . . . . . . . 26
-
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-Barbato Expires August 24, 2006 [Page 2]
-
-Internet-Draft draft-ietf-avt-vorbis-rtp-00 February 2006
-
-
-1. Introduction
-
- Vorbis is a general purpose perceptual audio codec intended to allow
- maximum encoder flexibility, thus allowing it to scale competitively
- over an exceptionally wide range of bitrates. At the high quality/
- bitrate end of the scale (CD or DAT rate stereo, 16/24 bits), it is
- in the same league as MPEG-2 and MPC. Similarly, the version 1.1
- reference encoder can encode high-quality CD and DAT rate stereo at
- below 48k bits/sec without resampling to a lower rate. Vorbis is
- also intended for lower and higher sample rates (from 8kHz telephony
- to 192kHz digital masters) and a range of channel representations
- (monaural, polyphonic, stereo, quadraphonic, 5.1, ambisonic, or up to
- 255 discrete channels).
-
- Vorbis encoded audio is generally encapsulated within an Ogg format
- bitstream [1], which provides framing and synchronization. For the
- purposes of RTP transport, this layer is unnecessary, and so raw
- Vorbis packets are used in the payload.
-
-1.1. Terminology
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
- document are to be interpreted as described in RFC 2119 [2].
-
-
-2. Payload Format
-
- For RTP based transport of Vorbis encoded audio the standard RTP
- header is followed by a 4 octets payload header, then the payload
- data. The payload headers are used to associate the Vorbis data with
- its associated decoding codebooks as well as indicating if the
- following packet contains fragmented Vorbis data and/or the number of
- whole Vorbis data frames. The payload data contains the raw Vorbis
- bitstream information.
-
-2.1. RTP Header
-
- The format of the RTP header is specified in [3] and shown in Figure
- Figure 1. This payload format uses the fields of the header in a
- manner consistent with that specification.
-
-
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-Barbato Expires August 24, 2006 [Page 3]
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-Internet-Draft draft-ietf-avt-vorbis-rtp-00 February 2006
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- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 1: RTP Header
-
- The RTP header begins with an octet of fields (V, P, X, and CC) to
- support specialized RTP uses (see [3] and [4] for details). For
- Vorbis RTP, the following values are used.
-
- Version (V): 2 bits
-
- This field identifies the version of RTP. The version used by this
- specification is two (2).
-
- Padding (P): 1 bit
-
- Padding MAY be used with this payload format according to section 5.1
- of [3].
-
- Extension (X): 1 bit
-
- The Extension bit is used in accordance with [3].
-
- CSRC count (CC): 4 bits
-
- The CSRC count is used in accordance with [3].
-
- Marker (M): 1 bit
-
- Set to zero. Audio silence suppression not used. This conforms to
- section 4.1 of [15].
-
- Payload Type (PT): 7 bits
-
- An RTP profile for a class of applications is expected to assign a
- payload type for this format, or a dynamically allocated payload type
- SHOULD be chosen which designates the payload as Vorbis.
-
-
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-Barbato Expires August 24, 2006 [Page 4]
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- Sequence number: 16 bits
-
- The sequence number increments by one for each RTP data packet sent,
- and may be used by the receiver to detect packet loss and to restore
- packet sequence. This field is detailed further in [3].
-
- Timestamp: 32 bits
-
- A timestamp representing the sampling time of the first sample of the
- first Vorbis packet in the RTP packet. The clock frequency MUST be
- set to the sample rate of the encoded audio data and is conveyed out-
- of-band as a SDP parameter.
-
- SSRC/CSRC identifiers:
-
- These two fields, 32 bits each with one SSRC field and a maximum of
- 16 CSRC fields, are as defined in [3].
-
-2.2. Payload Header
-
- The 4 octets following the RTP Header section are the Payload Header.
- This header is split into a number of bitfields detailing the format
- of the following payload data packets.
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | F |VDT|# pkts.|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 2: Payload Header
-
- Ident: 24 bits
-
- This 24 bit field is used to associate the Vorbis data to a decoding
- Configuration.
-
- Fragment type (F): 2 bits
-
- This field is set according to the following list
-
- 0 = Not Fragmented
- 1 = Start Fragment
- 2 = Continuation Fragment
- 3 = End Fragment
-
- Vorbis Data Type (VDT): 2 bits
-
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-Barbato Expires August 24, 2006 [Page 5]
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- This field sets the payload type for the Vorbis data in this RTP
- packet. There are currently three type of Vorbis payloads.
-
- 0 = Raw Vorbis payload
- 1 = Vorbis Packed Configuration payload
- 2 = Legacy Vorbis Comment payload
- 3 = Reserved
-
- The packets with a TDT of value 3 MUST be ignored
-
- The last 4 bits represent the number of complete packets in this
- payload. This provides for a maximum number of 15 Vorbis packets in
- the payload. If the packet contains fragmented data the number of
- packets MUST be set to 0.
-
-2.3. Payload Data
-
- Raw Vorbis packets are currently unbounded in length, application
- profiles will likely define a practical limit. Typical Vorbis packet
- sizes range from very small (2-3 bytes) to quite large (8-12
- kilobytes). The reference implementation [14] typically produces
- packets less than ~800 bytes, except for the setup header packets
- which are ~4-12 kilobytes. Within an RTP context, to avoid
- fragmentation, the Vorbis data packet size SHOULD be kept
- sufficiently small so that after adding the the RTP and payload
- headers, the complete RTP packet is smaller than the path MTU.
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis packet data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 3: Payload Data Header
-
- Each Vorbis payload packet starts with a two octet length header,
- which is used to represent the size of the following data payload,
- followed by the raw Vorbis data padded to the nearest byte boundary.
-
- For payloads which consist of multiple Vorbis packets the payload
- data consists of the packet length followed by the packet data for
- each of the Vorbis packets in the payload.
-
- The Vorbis packet length header is the length of the Vorbis data
- block only and does not count the length field.
-
- The payload packing of the Vorbis data packets MUST follow the
- guidelines set-out in [4] where the oldest packet occurs immediately
-
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-Barbato Expires August 24, 2006 [Page 6]
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- after the RTP packet header. Subsequent packets, if any, MUST follow
- in temporal order.
-
- Channel mapping of the audio is in accordance with the Vorbis I
- Specification [15].
-
-2.4. Example RTP Packet
-
- Here is an example RTP packet containing two Vorbis packets.
-
- RTP Packet Header:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 2 |0|0| 0 |0| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp (in sample rate units) |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronisation source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 4: Example Packet (RTP Headers)
-
- Payload Data:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 0 | 2 pks |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | next vorbis packet data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 5: Example Packet (Payload Data)
-
- The payload data section of the RTP packet begins with the 24 bit
- Ident field followed by the one octet bitfield header, which has the
- number of Vorbis frames set to 2. Each of the Vorbis data frames is
-
-
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- prefixed by the two octets length field. The Packet Type and
- Fragment Type are set to 0. The Configuration that will be used to
- decode the packets is the one indexed by the ident value.
-
-
-3. Configuration Headers
-
- Unlike other mainstream audio codecs Vorbis has no statically
- configured probability model. Instead, it packs all entropy decoding
- configuration, VQ and Huffman models into a data block that must be
- transmitted to the decoder along with the compressed data. A decoder
- also requires information detailing the number of audio channels,
- bitrates and similar information to configure itself for a particular
- compressed data stream. These two blocks of information are often
- referred to collectively as the "codebooks" for a Vorbis stream, and
- are nominally included as special "header" packets at the start of
- the compressed data. In addition, the Vorbis I specification [15]
- requires the presence of a comment header packet which gives simple
- metadata about the stream, but this information is not required for
- decoding the frame sequence.
-
- Thus these two codebook header packets must be received by the
- decoder before any audio data can be interpreted. These requirements
- pose problems in RTP, which is often used over unreliable transports.
-
- Since this information must be transmitted reliably and, as the RTP
- stream may change certain configuration data mid-session, there are
- different methods for delivering this configuration data to a client,
- both in-band and out-of-band which is detailed below. SDP delivery
- is used to set up an initial state for the client application. The
- changes may be due to different codebooks as well as different
- bitrates of the stream.
-
- The delivery vectors in use are specified by an SDP attribute to
- indicate the method and the optional URI where the Vorbis Packed
- Configuration (Section 3.1.1) Packets could be fetched. Different
- delivery methods MAY be advertised for the same session. The in-band
- Configuration delivery SHOULD be considered as baseline, out-of-band
- delivery methods that don't use RTP will not be described in this
- document. For non chained streams, the Configuration recommended
- delivery method is inline the Packed Configuration (Section 3.1.1) in
- the SDP as explained in the IANA considerations (Section 6.1)
- section.
-
- The 24 bit Ident field is used to map which Configuration will be
- used to decode a packet. When the Ident field changes, it indicates
- that a change in the stream has taken place. The client application
- MUST have in advance the correct configuration and if the client
-
-
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- detects a change in the Ident value and does not have this
- information it MUST NOT decode the raw Vorbis data associated until
- it fetches the correct Configuration.
-
-3.1. In-band Header Transmission
-
- The Packed Configuration (Section 3.1.1) Payload is sent in-band with
- the packet type bits set to match the payload type. Clients MUST be
- capable of dealing with fragmentation and periodic re-transmission of
- the configuration headers.
-
-3.1.1. Packed Configuration
-
- A Vorbis Packed Configuration is indicated with the payload type
- field set to 1. Of the three headers, defined in the Vorbis I
- specification [15], the identification and the setup will be packed
- together, the comment header is completely suppressed. Is up to the
- client provide a minimal size comment header to the decoder if
- required by the implementation.
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-Barbato Expires August 24, 2006 [Page 9]
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- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | xxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 1 | 1|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. | Setup ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 6: Packed Configuration Figure
-
- The Ident field is set with the value that will be used by the Raw
- Payload Packets to address this Configuration. The Fragment type is
- set to 0 since the packet bears the full Packed configuration, the
- number of packet is set to 1.
-
-3.2. Out of Band Transmission
-
- This section, as stated above, does not cover all the possible out-
- of-band delivery methods since they rely on different protocols and
- are linked to specific applications. The following packet definition
- SHOULD be used in out-of-band delivery and MUST be used when
- Configuration is inlined in the SDP.
-
-3.2.1. Packed Headers
-
- As mentioned above the RECOMMENDED delivery vector for Vorbis
-
-
-
-Barbato Expires August 24, 2006 [Page 10]
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-
-
- configuration data is via a retrieval method that can be performed
- using a reliable transport protocol. As the RTP headers are not
- required for this method of delivery the structure of the
- configuration data is slightly different. The packed header starts
- with a 32 bit count field which details the number of packed headers
- that are contained in the bundle. Next is the Packed header payload
- for each chained Vorbis stream.
-
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Number of packed headers |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Packed header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Packed header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 7: Packed Headers Overview
-
- Since the Configuration Ident and the Identification Header are fixed
- length there is only a 2 byte length tag to define the length of the
- packed headers.
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. length | Identification Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Setup Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 8: Packed Headers Detail
-
- The key difference between the in-band format and this one, is there
- is no need for the payload header octet.
-
-3.2.1.1. Packed Headers IANA Considerations
-
- The following IANA considerations MUST only be applied to the packed
- headers.
-
-
-
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-
- MIME media type name: audio
-
- MIME subtype: vorbis-config
-
- Required Parameters:
-
- None
-
- Optional Parameters:
-
- None
-
- Encoding considerations:
-
- This media type contains binary data.
-
- Security Considerations:
-
- See Section 6 of RFC XXXX.
-
- Interoperability considerations:
-
- None
-
- Published specification:
-
- RFC XXXX [RFC Editor: please replace by the RFC number of this
- memo, when published]
-
- Applications which use this media type:
-
- Vorbis encoded audio, configuration data.
-
- Additional information:
-
- None
-
- Person & email address to contact for further information:
-
- Luca Barbato: <lu_zero at gentoo.org>
- IETF Audio/Video Transport Working Group
-
- Intended usage: COMMON
-
-
-
-
-
-
-
-
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-
-
- Restriction on usage:
-
- This media type doesn't depend on the transport.
-
- Author:
-
- Luca Barbato
-
- Change controller:
-
- IETF AVT Working Group
-
-3.3. Loss of Configuration Headers
-
- Unlike the loss of raw Vorbis payload data, loss of a configuration
- header can lead to a situation where it will not be possible to
- successfully decode the stream.
-
- Loss of Configuration Packet results in the halting of stream
- decoding and SHOULD be reported to the client as well as a loss
- report sent via RTCP.
-
-
-4. Comment Headers
-
- With the payload type flag set to 2, this indicates that the packet
- contain the comment metadata, such as artist name, track title and so
- on. These metadata messages are not intended to be fully descriptive
- but to offer basic track/song information. Clients MAY ignore it
- completely. The details on the format of the comments can be found
- in the Vorbis documentation [15].
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | xxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 2 | 1|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 9: Comment Packet
-
- The 2 bytes length field is necessary since this packet could be
- fragmented.
-
-
-5. Frame Packetization
-
- Each RTP packet contains either one Vorbis packet fragment, or an
- integer number of complete Vorbis packets (up to a maximum of 15
- packets, since the number of packets is defined by a 4 bit value).
-
- Any Vorbis data packet that is less than path MTU SHOULD be bundled
- in the RTP packet with as many Vorbis packets as will fit, up to a
- maximum of 15, except when such bundling would exceed an
- application's desired transmission latency. Path MTU is detailed in
- [6] and [7].
-
- A fragmented packet has a zero in the last four bits of the payload
- header. The first fragment will set the Fragment type to 1. Each
- fragment after the first will set the Fragment type to 2 in the
- payload header. The RTP packet containing the last fragment of the
- Vorbis packet will have the Fragment type set to 3. To maintain the
- correct sequence for fragmented packet reception the timestamp field
- of fragmented packets MUST be the same as the first packet sent, with
- the sequence number incremented as normal for the subsequent RTP
-
-
-
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-
-
- packets. The length field shows the fragment length.
-
-5.1. Example Fragmented Vorbis Packet
-
- Here is an example fragmented Vorbis packet split over three RTP
- packets. Each packet contains the standard RTP headers as well as
- the 4 octets Vorbis headers.
-
- Packet 1:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1000 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 1 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 10: Example Fragmented Packet (Packet 1)
-
- In this packet the initial sequence number is 1000 and the timestamp
- is xxxxx. The Fragment type is set to 1, the number of packets field
- is set to 0, and as the payload is raw Vorbis data the VDT field is
- set to 0.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-
- Packet 2:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1001 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 2 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 11: Example Fragmented Packet (Packet 2)
-
- The Fragment type field is set to 2 and the number of packets field
- is set to 0. For large Vorbis fragments there can be several of
- these type of payload packets. The maximum packet size SHOULD be no
- greater than the path MTU, including all RTP and payload headers.
- The sequence number has been incremented by one but the timestamp
- field remains the same as the initial packet.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-
- Packet 3:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1002 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 3 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 12: Example Fragmented Packet (Packet 3)
-
- This is the last Vorbis fragment packet. The Fragment type is set to
- 3 and the packet count remains set to 0. As in the previous packets
- the timestamp remains set to the first packet in the sequence and the
- sequence number has been incremented.
-
-5.2. Packet Loss
-
- As there is no error correction within the Vorbis stream, packet loss
- will result in a loss of signal. Packet loss is more of an issue for
- fragmented Vorbis packets as the client will have to cope with the
- handling of the Fragment Type. In case of loss of fragments the
- client MUST discard all the remaining fragments and decode the
- incomplete packet. If we use the fragmented Vorbis packet example
- above and the first packet is lost the client MUST detect that the
- next packet has the packet count field set to 0 and the Fragment type
- 2 and MUST drop it. The next packet, which is the final fragmented
- packet, MUST be dropped in the same manner. If the missing packet is
- the last, the received two fragments will be kept and the incomplete
- vorbis packet decoded. Feedback reports on lost and dropped packets
- MUST be sent back via RTCP.
-
- If a particular multicast session has a large number of participants
- care must be taken to prevent an RTCP feedback implosion, [10], in
- the event of packet loss from a large number of participants.
-
-
-
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-
-
- Loss of any of the Configuration fragment will result in the loss of
- the full Configuration packet with the result detailed in the Loss of
- Configuration Headers (Section 3.3) section.
-
-
-6. IANA Considerations
-
- MIME media type name: audio
-
- MIME subtype: vorbis
-
- Required Parameters:
-
- delivery-method: indicates the delivery methods in use, the
- possible values are: inline, in_band, out_band/specific_name
- Where "specific_name" is the name of the out of band delivery
- method.
-
- configuration: the base16 [9] (hexadecimal) representation of the
- Packed Headers (Section 3.2.1).
-
- Optional Parameters:
-
- configuration-uri: the URI of the configuration headers in case of
- out of band transmission. In the form of
- "protocol://path/to/resource/". Depending on the specific
- method the single ident packet could be retrived by their
- number, or aggregated in a single stream, aggregates MAY be
- compressed using bzip2 [13] or gzip [11] and an sha1 [12]
- checksum MAY be provided in the form of
- "protocol://path/to/resource/aggregated.bz2!sha1hash"
-
- Encoding considerations:
-
- This media type is framed and contains binary data.
-
- Security Considerations:
-
- See Section 6 of RFC XXXX.
-
- Interoperability considerations:
-
- None
-
-
-
-
-
-
-
-
-Barbato Expires August 24, 2006 [Page 18]
-
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-
-
- Published specification:
-
- RFC XXXX [RFC Editor: please replace by the RFC number of this
- memo, when published]
-
- Ogg Vorbis I specification: Codec setup and packet decode.
- Available from the Xiph website, http://www.xiph.org
-
- Applications which use this media type:
-
- Audio streaming and conferencing tools
-
- Additional information:
-
- None
-
- Person & email address to contact for further information:
-
- Luca Barbato: <lu_zero at gentoo.org>
- IETF Audio/Video Transport Working Group
-
- Intended usage:
-
- COMMON
-
- Restriction on usage:
-
- This media type depends on RTP framing, and hence is only defined
- for transfer via RTP [3]
-
- Author:
-
- Luca Barbato
-
- Change controller:
-
- IETF AVT Working Group
-
-
-6.1. Mapping MIME Parameters into SDP
-
- The information carried in the MIME media type specification has a
- specific mapping to fields in the Session Description Protocol (SDP)
- [5], which is commonly used to describe RTP sessions. When SDP is
- used to specify sessions the mapping are as follows:
-
-
-
-
-
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-
-
- o The MIME type ("audio") goes in SDP "m=" as the media name.
-
- o The MIME subtype ("vorbis") goes in SDP "a=rtpmap" as the encoding
- name.
-
- o The parameter "rate" also goes in "a=rtpmap" as clock rate.
-
- o The parameter "channels" also goes in "a=rtpmap" as channel count.
-
- o The mandated parameters "delivery-method" and "configuration" MUST
- be included in the SDP "a=fmpt" attribute.
-
- o The optional parameter "configuration-uri", when present, MUST be
- included in the SDP "a=fmpt" attribute and MUST follow the
- delivery-method that applies.
-
- If the stream comprises chained Vorbis files and all of them are
- known in advance, the Configuration Packet for each file SHOULD be
- passed to the client using the configuration attribute.
-
- The URI specified in the configuration-uri attribute MUST point to a
- location where all of the Configuration Packets needed for the life
- of the session reside.
-
- The port value is specified by the server application bound to the
- address specified in the c attribute. The bitrate value and channels
- specified in the rtpmap attribute MUST match the Vorbis sample rate
- value. An example is found below.
-
-6.1.1. SDP Example
-
- The following example shows a basic SDP single stream. The first
- configuration packet is inlined in the sdp, other configurations
- could be fetched at any time from the first provided uri using or all
- the known configuration could be downloaded using the second uri.
- The inline base16 [9] configuration string is omitted because of the
- lenght.
- c=IN IP4 192.0.0.1
- m=audio RTP/AVP 98
- a=rtpmap:98 vorbis/44100/2
- a=delivery:out_band/http
- a=fmtp:98 delivery-method=in_band; configuration=base16string1;
- delivery-method=out_band/rtsp;
- configuration-uri=rtsp://path/to/the/resource; delivery-
- method=out_band/http; configuration-uri=http://another/path/to/
- resource/aggregate.bz2!sha1hash;
-
- Note that the payload format (encoding) names are commonly shown in
-
-
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-
-
- upper case. MIME subtypes are commonly shown in lower case. These
- names are case-insensitive in both places. Similarly, parameter
- names are case-insensitive both in MIME types and in the default
- mapping to the SDP a=fmtp attribute. The exception regarding case
- sensitivity is the configuration-uri URI which MUST be regarded as
- being case sensitive.
-
-6.2. Usage with the SDP Offer/Answer Model
-
- The offer, as described in An Offer/Answer Model Session Description
- Protocol [8], may contain a large number of delivery methods per
- single fmtp attribute, the answerer MUST remove every delivery-method
- and configuration-uri not supported. All the parameters MUST not be
- altered on answer otherwise.
-
-
-7. Congestion Control
-
- Vorbis clients SHOULD send regular receiver reports detailing
- congestion. A mechanism for dynamically downgrading the stream,
- known as bitrate peeling, will allow for a graceful backing off of
- the stream bitrate. This feature is not available at present so an
- alternative would be to redirect the client to a lower bitrate stream
- if one is available.
-
- If a particular multicast session has a large number of participants
- care must be taken to prevent an RTCP feedback implosion, [10], in
- the event of congestion.
-
-
-8. Examples
-
- The following examples are common usage patterns that MAY be applied
- in such situations, the main scope of this section is to explain
- better usage of the transmission vectors.
-
-8.1. Stream Radio
-
- This is one of the most common situation: one single server streaming
- content in multicast, the clients may start a session at random time.
- The content itself could be a mix of live stream, as the wj's voice,
- and stored streams as the music she plays.
-
- In this situation we don't know in advance how many codebooks we will
- use. The clients can join anytime and users expect to start
- listening to the content in a short time.
-
- On join the client will receive the current Configuration necessary
-
-
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-
-
- to decode the current stream inlined in the SDP so that the decoding
- will start immediately after.
-
- When the streamed content changes the new Configuration is sent in-
- band before the actual stream, and the Configuration that has to be
- sent inline in the SDP updated. Since the inline method is
- unreliable, an out of band fallback is provided.
-
- The client could choose to fetch the Configuration from the alternate
- source as soon it discovers a Configuration packet got lost inline or
- use selective retransmission [17], if the server supports the
- feature.
-
- A serverside optimization would be to keep an hash list of the
- Configurations per session to avoid packing all of them and send the
- same Configuration with different Ident tags
-
- A clientside optimization would be to keep a tag list of the
- Configurations per session and don't process configuration packets
- already known.
-
-
-9. Security Considerations
-
- RTP packets using this payload format are subject to the security
- considerations discussed in the RTP specification [3]. This implies
- that the confidentiality of the media stream is achieved by using
- encryption. Because the data compression used with this payload
- format is applied end-to-end, encryption may be performed on the
- compressed data. Where the size of a data block is set care MUST be
- taken to prevent buffer overflows in the client applications.
-
-
-10. Acknowledgments
-
- This document is a continuation of draft-moffitt-vorbis-rtp-00.txt
- and draft-kerr-avt-vorbis-rtp-04.txt. The MIME type section is a
- continuation of draft-short-avt-rtp-vorbis-mime-00.txt.
-
- Thanks to the AVT, Ogg Vorbis Communities / Xiph.org including Steve
- Casner, Aaron Colwell, Ross Finlayson, Fluendo, Ramon Garcia, Pascal
- Hennequin, Ralph Giles, Tor-Einar Jarnbjo, Colin Law, John Lazzaro,
- Jack Moffitt, Christopher Montgomery, Colin Perkins, Barry Short,
- Mike Smith, Phil Kerr, Michael Sparks, Magnus Westerlund, David
- Barrett, Silvia Pfeiffer, Stefan Ehmann, Alessandro Salvatori.
- Politecnico di Torino (LS)^3/IMG Group in particular Federico
- Ridolfo, Francesco Varano, Giampaolo Mancini, Juan Carlos De Martin.
-
-
-
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-
-
-11. References
-
-11.1. Normative References
-
- [1] Pfeiffer, S., "The Ogg Encapsulation Format Version 0",
- RFC 3533.
-
- [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
- Levels", RFC 2119.
-
- [3] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
- "RTP: A Transport Protocol for real-time applications",
- RFC 3550.
-
- [4] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
- Conferences with Minimal Control.", RFC 3551.
-
- [5] Handley, M. and V. Jacobson, "SDP: Session Description
- Protocol", RFC 2327.
-
- [6] Mogul et al., J., "Path MTU Discovery", RFC 1063.
-
- [7] McCann et al., J., "Path MTU Discovery for IP version 6",
- RFC 1981.
-
- [8] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
- Session Description Protocol (SDP)", RFC 3264.
-
- [9] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings",
- RFC 3548.
-
- [10] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
- "Extended RTP Profile for RTCP-based Feedback (RTP/AVPF)",
- Internet Draft (draft-ietf-avt-rtcp-feedback-11: Work in
- progress).
-
- [11] Deutsch, P., "GZIP file format specification version 4.3",
- RFC 1952.
-
- [12] National Institute of Standards and Technology, "Secure Hash
- Standard", May 1993.
-
- [13] Seward, J., "libbz2 and bzip2".
-
-11.2. Informative References
-
- [14] "libvorbis: Available from the Xiph website,
- http://www.xiph.org".
-
-
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-
-
- [15] "Ogg Vorbis I specification: Codec setup and packet decode.
- Available from the Xiph website, http://www.xiph.org".
-
- [16] "Ogg Vorbis I specification: Comment field and header
- specification. Available from the Xiph website,
- http://www.xiph.org".
-
- [17] Friedman, T., Caceres, R., and A. Clark, "RTP Control Protocol
- Extended Reports (RTCP XR)", RFC 3611, November 2003.
-
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-Author's Address
-
- Luca Barbato
- Xiph.Org
-
- Email: lu_zero at gentoo.org
- URI: http://www.xiph.org/
-
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-Intellectual Property Statement
-
- The IETF takes no position regarding the validity or scope of any
- Intellectual Property Rights or other rights that might be claimed to
- pertain to the implementation or use of the technology described in
- this document or the extent to which any license under such rights
- might or might not be available; nor does it represent that it has
- made any independent effort to identify any such rights. Information
- on the procedures with respect to rights in RFC documents can be
- found in BCP 78 and BCP 79.
-
- Copies of IPR disclosures made to the IETF Secretariat and any
- assurances of licenses to be made available, or the result of an
- attempt made to obtain a general license or permission for the use of
- such proprietary rights by implementers or users of this
- specification can be obtained from the IETF on-line IPR repository at
- http://www.ietf.org/ipr.
-
- The IETF invites any interested party to bring to its attention any
- copyrights, patents or patent applications, or other proprietary
- rights that may cover technology that may be required to implement
- this standard. Please address the information to the IETF at
- ietf-ipr at ietf.org.
-
-
-Disclaimer of Validity
-
- This document and the information contained herein are provided on an
- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
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- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
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-
-Copyright Statement
-
- Copyright (C) The Internet Society (2006). This document is subject
- to the rights, licenses and restrictions contained in BCP 78, and
- except as set forth therein, the authors retain all their rights.
-
-
-Acknowledgment
-
- Funding for the RFC Editor function is currently provided by the
- Internet Society.
-
-
-
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-
-
Deleted: trunk/vorbis/doc/draft-ietf-avt-vorbis-rtp-00.xml
===================================================================
--- trunk/vorbis/doc/draft-ietf-avt-vorbis-rtp-00.xml 2006-03-20 20:15:52 UTC (rev 11040)
+++ trunk/vorbis/doc/draft-ietf-avt-vorbis-rtp-00.xml 2006-03-20 20:20:37 UTC (rev 11041)
@@ -1,1198 +0,0 @@
-<?xml version='1.0'?>
-<!DOCTYPE rfc SYSTEM 'rfc2629.dtd'>
-<?rfc toc="yes" ?>
-<?rfc compact='yes'?>
-
-<rfc ipr="full3978" docName="RTP Payload Format for Vorbis Encoded Audio">
-
-<front>
-<title>draft-ietf-avt-vorbis-rtp-00</title>
-
-<author initials="L" surname="Barbato" fullname="Luca Barbato">
-<organization>Xiph.Org</organization>
-<address>
-<email>lu_zero at gentoo.org</email>
-<uri>http://www.xiph.org/</uri>
-</address>
-</author>
-
-<date day="20" month="February" year="2006" />
-
-<area>General</area>
-<workgroup>AVT Working Group</workgroup>
-<keyword>I-D</keyword>
-
-<keyword>Internet-Draft</keyword>
-<keyword>Vorbis</keyword>
-<keyword>RTP</keyword>
-
-<abstract>
-<t>
-This document describes an RTP payload format for transporting Vorbis encoded audio. It details the RTP encapsulation mechanism for raw Vorbis data and details the delivery mechanisms for the decoder probability model, referred to as a codebook and other setup information.
-</t>
-
-<t>
-Also included within the document are the necessary details for the use of Vorbis with MIME and Session Description Protocol (SDP).
-</t>
-
-</abstract>
-
-<note title="Editors Note">
-<t>
-All references to RFC XXXX are to be replaced by references to the RFC number of this memo, when published.
-</t>
-</note>
-
-</front>
-
-<middle>
-
-<section anchor="Introduction" title="Introduction">
-
-<t>
-Vorbis is a general purpose perceptual audio codec intended to allow
-maximum encoder flexibility, thus allowing it to scale competitively
-over an exceptionally wide range of bitrates. At the high
-quality/bitrate end of the scale (CD or DAT rate stereo, 16/24 bits), it
-is in the same league as MPEG-2 and MPC.
-Similarly, the version 1.1 reference encoder can encode high-quality CD
-and DAT rate stereo at below 48k bits/sec without resampling to a lower
-rate. Vorbis is also intended for lower and higher sample rates (from
-8kHz telephony to 192kHz digital masters) and a range of channel
-representations (monaural, polyphonic, stereo, quadraphonic, 5.1,
-ambisonic, or up to 255 discrete channels).
-</t>
-
-<t>
-Vorbis encoded audio is generally encapsulated within an Ogg format bitstream <xref target="rfc3533"></xref>, which provides
-framing and synchronization. For the purposes of RTP transport, this layer is unnecessary, and so raw Vorbis packets are used
-in the payload.
-</t>
-
-<section anchor="Terminology" title="Terminology">
-
-<t>
-The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
-in this document are to be interpreted as described in RFC 2119 <xref target="rfc2119"></xref>.
-</t>
-
-</section>
-</section>
-
-<section anchor="Payload Format" title="Payload Format">
-
-<t>
-For RTP based transport of Vorbis encoded audio the standard RTP header is followed by a 4 octets payload header, then the payload data. The payload headers are used to associate the Vorbis data with its associated decoding codebooks as well as indicating if the following packet contains fragmented Vorbis data and/or the number of whole Vorbis data frames. The payload data contains the raw Vorbis bitstream information.
-</t>
-
-<section anchor="RTP Header" title="RTP Header">
-
-<t>
-The format of the RTP header is specified in <xref target="rfc3550"></xref> and shown in Figure <xref target="RTP Header Figure"/>. This payload format uses the fields of the header in a manner consistent with that specification.
-</t>
-
-<t>
-<figure anchor="RTP Header Figure" title="RTP Header">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-</t>
-
-<t>
-The RTP header begins with an octet of fields (V, P, X, and CC) to support specialized RTP uses (see <xref target="rfc3550">
-</xref> and <xref target="rfc3551"></xref> for details). For Vorbis RTP, the following values are used.
-</t>
-
-<t>
-Version (V): 2 bits</t>
-<t>
-This field identifies the version of RTP. The version used by this specification is two (2).
-</t>
-
-<t>
-Padding (P): 1 bit</t>
-<t>
-Padding MAY be used with this payload format according to section 5.1 of <xref target="rfc3550"></xref>.
-</t>
-
-<t>
-Extension (X): 1 bit</t>
-<t>
-The Extension bit is used in accordance with <xref target="rfc3550"></xref>.
-</t>
-
-<t>
-CSRC count (CC): 4 bits</t>
-<t>
-The CSRC count is used in accordance with <xref target="rfc3550"></xref>.
-</t>
-
-<t>
-Marker (M): 1 bit</t>
-<t>
-Set to zero. Audio silence suppression not used. This conforms to section 4.1 of <xref target="vorbis-spec-ref"></xref>.
-</t>
-
-<t>
-Payload Type (PT): 7 bits</t>
-<t>
-An RTP profile for a class of applications is expected to assign a payload type for this format, or a dynamically allocated
-payload type SHOULD be chosen which designates the payload as Vorbis.
-</t>
-
-<t>
-Sequence number: 16 bits</t>
-<t>
-The sequence number increments by one for each RTP data packet sent, and may be used by the receiver to detect packet loss and
-to restore packet sequence. This field is detailed further in <xref target="rfc3550"></xref>.
-</t>
-
-<t>
-Timestamp: 32 bits</t>
-<t>
-A timestamp representing the sampling time of the first sample of the first Vorbis packet in the RTP packet. The clock frequency
-MUST be set to the sample rate of the encoded audio data and is conveyed out-of-band as a SDP parameter.
-</t>
-
-<t>
-SSRC/CSRC identifiers: </t>
-<t>
-These two fields, 32 bits each with one SSRC field and a maximum of 16 CSRC fields, are as defined in <xref target="rfc3550">
-</xref>.
-</t>
-
-</section>
-
-<section anchor="Payload Header" title="Payload Header">
-
-<t>
-The 4 octets following the RTP Header section are the Payload Header. This header is split into a number of bitfields detailing the format of the following payload data packets.
-</t>
-
-<figure anchor="Payload Header Figure" title="Payload Header">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | F |VDT|# pkts.|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-Ident: 24 bits</t>
-<t>
-This 24 bit field is used to associate the Vorbis data to a decoding Configuration.
-</t>
-
-<t>
-Fragment type (F): 2 bits</t>
-<t>
-This field is set according to the following list
-</t>
-<vspace blankLines="1" />
-<list style="empty">
-<t> 0 = Not Fragmented</t>
-<t> 1 = Start Fragment</t>
-<t> 2 = Continuation Fragment</t>
-<t> 3 = End Fragment</t>
-</list>
-
-<t>
-Vorbis Data Type (VDT): 2 bits</t>
-<t>
-This field sets the payload type for the Vorbis data in this RTP packet. There are currently three type of Vorbis payloads.
-</t>
-
-<vspace blankLines="1" />
-<list style="empty">
-<t> 0 = Raw Vorbis payload</t>
-<t> 1 = Vorbis Packed Configuration payload</t>
-<t> 2 = Legacy Vorbis Comment payload</t>
-<t> 3 = Reserved</t>
-</list>
-
-<t> The packets with a TDT of value 3 MUST be ignored </t>
-
-<t>
-The last 4 bits represent the number of complete packets in this payload. This provides for a maximum number of 15 Vorbis packets in the payload. If the packet contains fragmented data the number of packets MUST be set to 0.
-</t>
-
-</section>
-
-<section anchor="Payload Data" title="Payload Data">
-
-<t>
-Raw Vorbis packets are currently unbounded in length, application profiles will likely define a practical limit. Typical Vorbis packet sizes range from very small (2-3 bytes) to quite large (8-12 kilobytes). The reference implementation <xref target="libvorbis"></xref> typically produces packets less than ~800 bytes, except for the setup header packets which are ~4-12 kilobytes. Within an RTP context, to avoid fragmentation, the Vorbis data packet size SHOULD be kept sufficiently small so that after adding the the RTP and payload headers, the complete RTP packet is smaller than the path MTU.
-</t>
-
-<figure anchor="Payload Data Figure" title="Payload Data Header">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis packet data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-Each Vorbis payload packet starts with a two octet length header, which is used to represent the size of the following data payload, followed by the raw Vorbis data padded to the nearest byte boundary.
-</t>
-
-<t>
-For payloads which consist of multiple Vorbis packets the payload data consists of the packet length followed by the packet data for each of the Vorbis packets in the payload.
-</t>
-
-<t>
-The Vorbis packet length header is the length of the Vorbis data block only and does not count the length field.
-</t>
-
-<t>
-The payload packing of the Vorbis data packets MUST follow the guidelines set-out in <xref target="rfc3551"></xref> where the oldest packet occurs immediately after the RTP packet header. Subsequent packets, if any, MUST follow in temporal order.
-</t>
-
-<t>
-Channel mapping of the audio is in accordance with the <xref target="vorbis-spec-ref">Vorbis I Specification</xref>.
-</t>
-
-</section>
-
-<section anchor="Example RTP Packet" title="Example RTP Packet">
-
-<t>
-Here is an example RTP packet containing two Vorbis packets.
-</t>
-
-<t>
-RTP Packet Header:
-</t>
-
-<figure anchor="Example Header Packet (RTP Headers)" title="Example Packet (RTP Headers)">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 2 |0|0| 0 |0| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp (in sample rate units) |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronisation source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-Payload Data:
-</t>
-
-<figure anchor="Example Packet (Payload Data)" title="Example Packet (Payload Data)">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 0 | 2 pks |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | next vorbis packet data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-The payload data section of the RTP packet begins with the 24 bit Ident field followed by the one octet bitfield header, which has the number of Vorbis frames set to 2. Each of the Vorbis data frames is prefixed by the two octets length field. The Packet Type and Fragment Type are set to 0. The Configuration that will be used to decode the packets is the one indexed by the ident value.
-</t>
-
-</section>
-</section>
-
-
-
-<section anchor="Configuration Headers" title="Configuration Headers">
-
-<t>
-Unlike other mainstream audio codecs Vorbis has no statically
-configured probability model. Instead, it packs all entropy decoding
-configuration, VQ and Huffman models into a data block that must be
-transmitted to the decoder along with the compressed data. A decoder
-also requires information detailing the number of audio
-channels, bitrates and similar information to configure itself for a
-particular compressed data stream. These two blocks of information are
-often referred to collectively as the "codebooks" for a Vorbis stream,
-and are nominally included as special "header" packets at the start
-of the compressed data. In addition,
-the <xref target="vorbis-spec-ref">Vorbis I specification</xref>
-requires the presence of a comment header packet which gives simple
-metadata about the stream, but this information is not required for
-decoding the frame sequence.
-</t>
-
-<t>
-Thus these two codebook header packets must be received by the decoder
-before any audio data can be interpreted.
- These requirements pose problems in RTP,
-which is often used over unreliable transports.
-</t>
-
-<t>
-Since this information must be transmitted reliably and, as the RTP
-stream may change certain configuration data mid-session, there are
-different methods for delivering this configuration data to a
-client, both in-band and out-of-band which is detailed below. SDP
-delivery is used to set up an initial state for the client application.
-The changes may be due to different codebooks as well as different
-bitrates of the stream.
-</t>
-
-<t>
-The delivery vectors in use are specified by an SDP attribute to indicate the method and the optional URI where the Vorbis <xref target="Packed Configuration">Packed Configuration</xref> Packets could be fetched. Different delivery methods MAY be advertised for the same session. The in-band Configuration delivery SHOULD be considered as baseline, out-of-band delivery methods that don't use RTP will not be described in this document. For non chained streams, the Configuration recommended delivery method is inline the <xref target="Packed Configuration">Packed Configuration</xref> in the SDP as explained in the <xref target="Mapping MIME Parameters into SDP"> IANA considerations</xref> section.
-</t>
-
-<t>
-The 24 bit Ident field is used to map which Configuration will be used to decode a packet. When the Ident field changes, it indicates that a change in the stream has taken place. The client application MUST have in advance the correct configuration and if the client detects a change in the Ident value and does not have this information it MUST NOT decode the raw Vorbis data associated until it fetches the correct Configuration.
-</t>
-
-<section anchor="In-band Header Transmission" title="In-band Header Transmission">
-
-<t>
-The <xref target="Packed Configuration">Packed Configuration</xref> Payload is sent in-band with the packet type bits set to match the payload type. Clients MUST be capable of dealing with fragmentation and periodic re-transmission of the configuration headers.
-</t>
-
-<section anchor="Packed Configuration" title="Packed Configuration">
-
-<t>
-A Vorbis Packed Configuration is indicated with the payload type field set to 1. Of the three headers, defined in the <xref target="vorbis-spec-ref">Vorbis I specification</xref>, the identification and the setup will be packed together, the comment header is completely suppressed. Is up to the client provide a minimal size comment header to the decoder if required by the implementation.
-</t>
-
-<figure anchor="Packed Configuration Figure" title="Packed Configuration Figure">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | xxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 1 | 1|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. | Setup ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>The Ident field is set with the value that will be used by the Raw Payload Packets to address this Configuration. The Fragment type is set to 0 since the packet bears the full Packed configuration, the number of packet is set to 1.</t>
-</section>
-</section>
-
-<section anchor="Out of Band Transmission" title="Out of Band Transmission">
-
-
-<t>
-This section, as stated above, does not cover all the possible out-of-band delivery methods since they rely on different protocols and are linked to specific applications. The following packet definition SHOULD be used in out-of-band delivery and MUST be used when Configuration is inlined in the SDP.
-</t>
-
-<section anchor="Packed Headers" title="Packed Headers">
-
-<t>
-As mentioned above the RECOMMENDED delivery vector for Vorbis configuration data is via a retrieval method that can be performed using a reliable transport protocol. As the RTP headers are not required for this method of delivery the structure of the configuration data is slightly different. The packed header starts with a 32 bit count field which details the number of packed headers that are contained in the bundle. Next is the Packed header payload for each chained Vorbis stream.
-</t>
-
-<figure anchor="Packed Headers Overview Figure" title="Packed Headers Overview">
-<artwork><![CDATA[
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Number of packed headers |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Packed header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Packed header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-Since the Configuration Ident and the Identification Header are fixed length there is only a 2 byte length tag to define the length of the packed headers.
-</t>
-
-<figure anchor="Packed Headers Detail Figure" title="Packed Headers Detail">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. length | Identification Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Setup Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-<t>
-The key difference between the in-band format and this one, is there is no need for the payload header octet.
-</t>
-
-<section anchor="Packed Headers IANA Considerations" title="Packed Headers IANA Considerations">
-
-<t>
-The following IANA considerations MUST only be applied to the packed headers.
-</t>
-
-<vspace blankLines="1" />
-
-<list style="hanging">
-<t hangText="MIME media type name:"> audio </t>
-
-<vspace blankLines="1" />
-
-<t hangText="MIME subtype:"> vorbis-config </t>
-
-<vspace blankLines="1" />
-
-<t hangText="Required Parameters:">
-<vspace blankLines="1" />
-None
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Optional Parameters:">
-<vspace blankLines="1" />
-None
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Encoding considerations:">
-<vspace blankLines="1" />
-This media type contains binary data.
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Security Considerations:">
-<vspace blankLines="1" />
-See Section 6 of RFC XXXX.
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Interoperability considerations:">
-<vspace blankLines="1" />
-None
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Published specification:">
-<vspace blankLines="1" />
-RFC XXXX [RFC Editor: please replace by the RFC number of this memo,
- when published]
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Applications which use this media type:">
-<vspace blankLines="1" />
-Vorbis encoded audio, configuration data.
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Additional information:">
-<vspace blankLines="1" />
-None
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Person & email address to contact for further information:">
-<vspace blankLines="1" />
-Luca Barbato: <lu_zero at gentoo.org>
-<vspace blankLines="0" />
-IETF Audio/Video Transport Working Group
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Intended usage:">
-COMMON
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Restriction on usage:">
-<vspace blankLines="1" />
-This media type doesn't depend on the transport.
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Author:">
-<vspace blankLines="1" />
-Luca Barbato</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Change controller:">
-<vspace blankLines="1" />
-IETF AVT Working Group</t>
-</list>
-
-</section>
-</section>
-
-<!--
-<section anchor="Well Known Configurations" title="Well Known Configurations">
-
-<t>
-Even if the Vorbis nature prevents the creation of everlasting profiles, some combination of codebooks, bitrate, channels and samplerate are quite common.
-A client may have a list of well known configuration and MAY avoid fetching them already.
-In order to retain compatibility the server, even if all the Configurations that will be in use are Well Known, MUST provide at least another way to provide codebooks.
-Every Configuration that is available as Well Known has the Ident highest bit set. Every Well Known List MUST contain at most 2^23 items.
-</t>
-
-<t>
-This off band delivery method MUST be signaled as "out_band/wkc/list_name" using the mandated parameter delivery-method. An optional configuration-uri MAY point to a location where to fetch it. The list is in the form of <xref target="Packed Headers">Packed Headers</xref>, that MAY be compressed using <xref target="BZ2">bzip2</xref> or <xref target="rfc1952">gzip</xref> as further explained in the <xref target="IANA Considerations">IANA Considerations</xref> section.
-</t>
-
-<t>
-Only one list MUST be used at time. During <xref target="rfc3264">SDP Offer/Answer</xref> client and server MAY agree on a specific list, that subject will be discussed further on the specific <xref target="Usage with the SDP Offer/Answer Mode">SDP Offer/Answer</xref> section.
-This method
-</t>
-
-</section>
--->
-</section>
-
-<section anchor="Loss of Configuration Headers" title="Loss of Configuration Headers">
-
-<t>
-Unlike the loss of raw Vorbis payload data, loss of a configuration header can lead to a situation where it will not be possible to successfully decode the stream.
-</t>
-
-<t>
-Loss of Configuration Packet results in the halting of stream decoding and SHOULD be reported to the client as well as a loss report sent via RTCP.
-</t>
-
-</section>
-
-<!-- <section anchor="Mapping between Configuration and Stream" title="Mapping between Configuration and Stream">
-
-<t>
-The mapping between the stream and the the configuration is explicit.
-</t>
-
-</section> -->
-
-
-</section>
-
-<section anchor="Comment Headers" title="Comment Headers">
-
-<t>
-With the payload type flag set to 2, this indicates that the packet contain the comment metadata, such as artist name, track title and so on. These metadata messages are not intended to be fully descriptive but to offer basic track/song information. Clients MAY ignore it completely. The details on the format of the comments can be found in the <xref target="vorbis-spec-ref">Vorbis documentation</xref>.
-</t>
-<figure anchor="Comment Packet Figure" title="Comment Packet">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | xxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 2 | 1|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>The 2 bytes length field is necessary since this packet could be fragmented.</t>
-
-</section>
-<section anchor="Frame Packetization" title="Frame Packetization">
-
-<t>
-Each RTP packet contains either one Vorbis packet fragment, or an integer number of complete Vorbis packets (up to a maximum of 15 packets, since the number of packets is defined by a 4 bit value).
-</t>
-
-<t>
-Any Vorbis data packet that is less than path MTU SHOULD be bundled in the RTP packet with as many Vorbis packets as will fit, up to a maximum of 15, except when such bundling would exceed an application's desired transmission latency. Path MTU is detailed in <xref target="rfc1063"></xref> and <xref target="rfc1981"></xref>.
-</t>
-
-<t>
-A fragmented packet has a zero in the last four bits of the payload header. The first fragment will set the Fragment type to 1. Each fragment after the first will set the Fragment type to 2 in the payload header. The RTP packet containing the last fragment of the Vorbis packet will have the Fragment type set to 3. To maintain the correct sequence for fragmented packet reception the timestamp field of fragmented packets MUST be the same as the first packet sent, with the sequence number incremented as normal for the subsequent RTP packets. The length field shows the fragment length.
-</t>
-
-<section anchor="Example Fragmented Vorbis Packet" title="Example Fragmented Vorbis Packet">
-
-<t>
-Here is an example fragmented Vorbis packet split over three RTP packets. Each packet contains the standard RTP headers as well as the 4 octets Vorbis headers.
-</t>
-
-<figure anchor="Example Fragmented Packet (Packet 1)" title="Example Fragmented Packet (Packet 1)">
-<artwork><![CDATA[
- Packet 1:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1000 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 1 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-In this packet the initial sequence number is 1000 and the timestamp is xxxxx. The Fragment type is set to 1, the number of packets field is set to 0, and as the payload is raw Vorbis data the VDT field is set to 0.
-</t>
-
-<figure anchor="Example Fragmented Packet (Packet 2)" title="Example Fragmented Packet (Packet 2)">
-<artwork><![CDATA[
- Packet 2:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1001 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 2 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-The Fragment type field is set to 2 and the number of packets field is set to 0. For large Vorbis fragments there can be several of these type of payload packets. The maximum packet size SHOULD be no greater than the path MTU, including all RTP and payload headers. The sequence number has been incremented by one but the timestamp field remains the same as the initial packet.
-</t>
-
-<figure anchor="Example Fragmented Packet (Packet 3)" title="Example Fragmented Packet (Packet 3)">
-<artwork><![CDATA[
- Packet 3:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1002 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 3 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-This is the last Vorbis fragment packet. The Fragment type is set to 3 and the packet count remains set to 0. As in the previous packets the timestamp remains set to the first packet in the sequence and the sequence number has been incremented.
-</t>
-</section>
-
-<section anchor="Packet Loss" title="Packet Loss">
-
-<t>
-As there is no error correction within the Vorbis stream, packet loss will result in a loss of signal. Packet loss is more of an issue for fragmented Vorbis packets as the client will have to cope with the handling of the Fragment Type. In case of loss of fragments the client MUST discard all the remaining fragments and decode the incomplete packet. If we use the fragmented Vorbis packet example above and the first packet is lost the client MUST detect that the next packet has the packet count field set to 0 and the Fragment type 2 and MUST drop it. The next packet, which is the final fragmented packet, MUST be dropped in the same manner. If the missing packet is the last, the received two fragments will be kept and the incomplete vorbis packet decoded. Feedback reports on lost and dropped packets MUST be sent back via RTCP.
-</t>
-
-<t>
-If a particular multicast session has a large number of participants care must be taken to prevent an RTCP feedback implosion, <xref target="rtcp-feedback"></xref>, in the event of packet loss from a large number of participants.
-</t>
-
-<t>
-Loss of any of the Configuration fragment will result in the loss of the full Configuration packet with the result detailed in the <xref target="Loss of Configuration Headers">Loss of Configuration Headers</xref> section.
-</t>
-
-</section>
-</section>
-<section anchor="IANA Considerations" title="IANA Considerations">
-
-<vspace blankLines="1" />
-
-<list style="hanging">
-<t hangText="MIME media type name:"> audio </t>
-
-<vspace blankLines="1" />
-
-<t hangText="MIME subtype:"> vorbis </t>
-
-<vspace blankLines="1" />
-
-<t hangText="Required Parameters:">
-
-<vspace blankLines="1" />
-
-<list style="hanging">
-<t hangText="delivery-method:"> indicates the delivery methods in use, the possible values are: inline, in_band, out_band/specific_name<vspace blankLines="0" />
-Where "specific_name" is the name of the out of band delivery method.
-
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="configuration:"> the <xref target="rfc3548">base16</xref> (hexadecimal) representation of the <xref target="Packed Headers">Packed Headers</xref>.
-</t>
-</list>
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Optional Parameters:">
-
-<vspace blankLines="1" />
-
-<list style="hanging">
-<t hangText="configuration-uri:"> the URI of the configuration headers in case of out of band transmission. In the form of "protocol://path/to/resource/". Depending on the specific method the single ident packet could be retrived by their number, or aggregated in a single stream, aggregates MAY be compressed using <xref target="BZ2">bzip2</xref> or <xref target="rfc1952">gzip</xref> and an <xref target="FIPS180">sha1</xref> checksum MAY be provided in the form of "protocol://path/to/resource/aggregated.bz2!sha1hash"</t>
-</list>
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Encoding considerations:">
-<vspace blankLines="1" />
-This media type is framed and contains binary data.
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Security Considerations:">
-<vspace blankLines="1" />
-See Section 6 of RFC XXXX.</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Interoperability considerations:">
-<vspace blankLines="1" />
-None</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Published specification:">
-
-<vspace blankLines="1" />
-
-<t> RFC XXXX [RFC Editor: please replace by the RFC number of this memo, when published]</t>
-<vspace blankLines="1" />
-<t>Ogg Vorbis I specification: Codec setup and packet decode. Available from the Xiph website, http://www.xiph.org</t>
-
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Applications which use this media type:">
-<vspace blankLines="1"/>
-Audio streaming and conferencing tools </t>
-
-<vspace blankLines="1" />
-
-<t hangText="Additional information:">
-<vspace blankLines="1" />
-None </t>
-
-<vspace blankLines="1" />
-
-<t hangText="Person & email address to contact for further information:">
-
-<vspace blankLines="1" />
-
-<t>Luca Barbato: <lu_zero at gentoo.org></t>
-<t>IETF Audio/Video Transport Working Group</t>
-
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Intended usage:">
-<vspace blankLines="1" />
-COMMON</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Restriction on usage:">
-<vspace blankLines="1" />
-This media type depends on RTP framing, and hence is only defined for transfer via <xref target="rfc3550">RTP</xref></t>
-
-<vspace blankLines="1" />
-
-<t hangText="Author:">
-<vspace blankLines="1"/>Luca Barbato</t>
-
-<vspace blankLines="1" />
-
-<t hangText="Change controller:"><vspace blankLines="1"/> IETF AVT Working Group</t>
-
-<vspace blankLines="1" />
-
-</list>
-
-<section anchor="Mapping MIME Parameters into SDP" title="Mapping MIME Parameters into SDP">
-
-<t>
-The information carried in the MIME media type specification has a specific mapping to fields in the Session Description Protocol (SDP) <xref target="rfc2327"></xref>, which is commonly used to describe RTP sessions. When SDP is used to specify sessions the mapping are as follows:
-</t>
-
-<vspace blankLines="1" />
-<list style="symbols">
-
-<t>The MIME type ("audio") goes in SDP "m=" as the media name.</t>
-<vspace blankLines="1" />
-
-<t>The MIME subtype ("vorbis") goes in SDP "a=rtpmap" as the encoding name.</t>
-<vspace blankLines="1" />
-
-<t>The parameter "rate" also goes in "a=rtpmap" as clock rate.</t>
-<vspace blankLines="1" />
-
-<t>The parameter "channels" also goes in "a=rtpmap" as channel count.</t>
-<vspace blankLines="1" />
-
-<t>The mandated parameters "delivery-method" and "configuration" MUST be included in the SDP "a=fmpt" attribute.</t>
-<vspace blankLines="1" />
-
-<t>The optional parameter "configuration-uri", when present, MUST be included in the SDP "a=fmpt" attribute and MUST follow the delivery-method that applies.</t>
-
-</list>
-
-<t>
-If the stream comprises chained Vorbis files and all of them are known in advance, the Configuration Packet for each file SHOULD be passed to the client using the configuration attribute.
-</t>
-
-<t>
-The URI specified in the configuration-uri attribute MUST point to a location where all of the Configuration Packets needed for the life of the session reside.
-</t>
-
-<t>
-The port value is specified by the server application bound to the address specified in the c attribute. The bitrate value and channels specified in the rtpmap attribute MUST match the Vorbis sample rate value. An example is found below.
-</t>
-
-<section anchor="SDP Example" title="SDP Example">
-<t>The following example shows a basic SDP single stream. The first configuration packet is inlined in the sdp, other configurations could be fetched at any time from the first provided uri using or all the known configuration could be downloaded using the second uri. The inline <xref target="rfc3548">base16</xref> configuration string is omitted because of the lenght.</t>
-
-<list style="empty">
-<t>c=IN IP4 192.0.0.1</t>
-<t>m=audio RTP/AVP 98</t>
-<t>a=rtpmap:98 vorbis/44100/2</t>
-<t>a=delivery:out_band/http</t>
-<t>a=fmtp:98 delivery-method=in_band; configuration=base16string1; delivery-method=out_band/rtsp; configuration-uri=rtsp://path/to/the/resource; delivery-method=out_band/http; configuration-uri=http://another/path/to/resource/aggregate.bz2!sha1hash;</t>
-</list>
-</section>
-
-
-<t>
-Note that the payload format (encoding) names are commonly shown in upper case. MIME subtypes are commonly shown in lower case. These names are case-insensitive in both places. Similarly, parameter names are case-insensitive both in MIME types and in the default mapping to the SDP a=fmtp attribute. The exception regarding case sensitivity is the configuration-uri URI which MUST be regarded as being case sensitive.
-</t>
-
-</section>
-
-<section anchor="Usage with the SDP Offer/Answer Mode" title="Usage with the SDP Offer/Answer Model">
-
-<t>
-The offer, as described in <xref target="rfc3264">An Offer/Answer Model Session Description Protocol</xref>, may contain a large number of delivery methods per single fmtp attribute, the answerer MUST remove every delivery-method and configuration-uri not supported. All the parameters MUST not be altered on answer otherwise.
-</t>
-
-</section>
-
-</section>
-
-<section anchor="Congestion Control" title="Congestion Control">
-
-<t>
-Vorbis clients SHOULD send regular receiver reports detailing congestion. A mechanism for dynamically downgrading the stream, known as bitrate peeling, will allow for a graceful backing off of the stream bitrate. This feature is not available at present so an alternative would be to redirect the client to a lower bitrate stream if one is available.
-</t>
-
-<t>
-If a particular multicast session has a large number of participants care must be taken to prevent an RTCP feedback implosion, <xref target="rtcp-feedback"></xref>, in the event of congestion.
-</t>
-
-</section>
-
-<section anchor="Examples" title="Examples">
-
-<t>
-The following examples are common usage patterns that MAY be applied in such situations, the main scope of this section is to explain better usage of the transmission vectors.
-</t>
-
-<section anchor="Stream Radio" title="Stream Radio">
-
-<t>This is one of the most common situation: one single server streaming content in multicast, the clients may start a session at random time. The content itself could be a mix of live stream, as the wj's voice, and stored streams as the music she plays.</t>
-
-<t>In this situation we don't know in advance how many codebooks we will use. The clients can join anytime and users expect to start listening to the content in a short time.</t>
-
-<t>On join the client will receive the current Configuration necessary to decode the current stream inlined in the SDP so that the decoding will start immediately after.</t>
-
-<t>When the streamed content changes the new Configuration is sent in-band before the actual stream, and the Configuration that has to be sent inline in the SDP updated. Since the inline method is unreliable, an out of band fallback is provided.</t>
-
-<t>The client could choose to fetch the Configuration from the alternate source as soon it discovers a Configuration packet got lost inline or use <xref target="RFC3611">selective retransmission</xref>, if the server supports the feature.</t>
-
-<t>A serverside optimization would be to keep an hash list of the Configurations per session to avoid packing all of them and send the same Configuration with different Ident tags</t>
-
-<t>A clientside optimization would be to keep a tag list of the Configurations per session and don't process configuration packets already known.</t>
-
-</section>
-</section>
-
-<section anchor="Security Considerations" title="Security Considerations">
-<t>
-RTP packets using this payload format are subject to the security considerations discussed in the RTP specification
-<xref target="rfc3550"></xref>. This implies that the confidentiality of the media stream is achieved by using
-encryption. Because the data compression used with this payload format is applied end-to-end, encryption may be performed on the
-compressed data. Where the size of a data block is set care MUST be taken to prevent buffer overflows in the client applications.
-</t>
-
-</section>
-
-<section anchor="Acknowledgments" title="Acknowledgments">
-
-<t>
-This document is a continuation of draft-moffitt-vorbis-rtp-00.txt and draft-kerr-avt-vorbis-rtp-04.txt. The MIME type section is a continuation of draft-short-avt-rtp-vorbis-mime-00.txt.
-</t>
-
-<t>
-Thanks to the AVT, Ogg Vorbis Communities / Xiph.org including Steve Casner, Aaron Colwell, Ross Finlayson, Fluendo, Ramon Garcia, Pascal Hennequin, Ralph Giles, Tor-Einar Jarnbjo, Colin Law, John Lazzaro, Jack Moffitt, Christopher Montgomery, Colin Perkins, Barry Short, Mike Smith, Phil Kerr, Michael Sparks, Magnus Westerlund, David Barrett, Silvia Pfeiffer, Stefan Ehmann, Alessandro Salvatori. Politecnico di Torino (LS)³/IMG Group in particular Federico Ridolfo, Francesco Varano, Giampaolo Mancini, Juan Carlos De Martin.
-</t>
-
-</section>
-
-</middle>
-
-<back>
-
-<references title="Normative References">
-
-<reference anchor="rfc3533">
-<front>
-<title>The Ogg Encapsulation Format Version 0</title>
-<author initials="S." surname="Pfeiffer" fullname="Silvia Pfeiffer"></author>
-</front>
-<seriesInfo name="RFC" value="3533" />
-</reference>
-
-<reference anchor="rfc2119">
-<front>
-<title>Key words for use in RFCs to Indicate Requirement Levels </title>
-<author initials="S." surname="Bradner" fullname="Scott Bradner"></author>
-</front>
-<seriesInfo name="RFC" value="2119" />
-</reference>
-
-<reference anchor="rfc3550">
-<front>
-<title>RTP: A Transport Protocol for real-time applications</title>
-<author initials="H." surname="Schulzrinne" fullname=""></author>
-<author initials="S." surname="Casner" fullname=""></author>
-<author initials="R." surname="Frederick" fullname=""></author>
-<author initials="V." surname="Jacobson" fullname=""></author>
-</front>
-<seriesInfo name="RFC" value="3550" />
-</reference>
-
-<reference anchor="rfc3551">
-<front>
-<title>RTP Profile for Audio and Video Conferences with Minimal Control.</title>
-<author initials="H." surname="Schulzrinne" fullname=""></author>
-<author initials="S." surname="Casner" fullname=""></author>
-</front>
-<date month="July" year="2003" />
-<seriesInfo name="RFC" value="3551" />
-</reference>
-
-<reference anchor="rfc2327">
-<front>
-<title>SDP: Session Description Protocol</title>
-<author initials="M." surname="Handley" fullname="Mark Handley"></author>
-<author initials="V." surname="Jacobson" fullname="Van Jacobson"></author>
-</front>
-<seriesInfo name="RFC" value="2327" />
-</reference>
-
-<reference anchor="rfc1063">
-<front>
-<title>Path MTU Discovery</title>
-<author initials="J." surname="Mogul et al." fullname="J. Mogul et al."></author>
-</front>
-<seriesInfo name="RFC" value="1063" />
-</reference>
-
-<reference anchor="rfc1981">
-<front>
-<title>Path MTU Discovery for IP version 6</title>
-<author initials="J." surname="McCann et al." fullname="J. McCann et al."></author>
-</front>
-<seriesInfo name="RFC" value="1981" />
-</reference>
-
-<reference anchor="rfc3264">
-<front>
-<title>An Offer/Answer Model with Session Description Protocol (SDP)</title>
-<author initials="J." surname="Rosenberg" fullname="Jonathan Rosenberg"></author>
-<author initials="H." surname="Schulzrinne" fullname="Henning Schulzrinne"></author>
-</front>
-<seriesInfo name="RFC" value="3264" />
-</reference>
-
-<reference anchor="rfc3548">
-<front>
-<title>The Base16, Base32, and Base64 Data Encodings</title>
-<author initials="S." surname="Josefsson" fullname="Simon Josefsson"></author>
-</front>
-<seriesInfo name="RFC" value="3548" />
-</reference>
-
-<reference anchor="rtcp-feedback">
-<front>
-<title>Extended RTP Profile for RTCP-based Feedback (RTP/AVPF)</title>
-<author initials="J." surname="Ott" fullname="Joerg Ott"></author>
-<author initials="S." surname="Wenger" fullname="Stephan Wenger"></author>
-<author initials="N." surname="Sato" fullname="Noriyuki Sato"></author>
-<author initials="C." surname="Burmeister" fullname="Carsten Burmeister"></author>
-<author initials="J." surname="Rey" fullname="Jose Rey"></author>
-</front>
-<seriesInfo name="Internet Draft" value="(draft-ietf-avt-rtcp-feedback-11: Work in progress)" />
-</reference>
-
-<reference anchor="rfc1952">
-<front>
-<title>GZIP file format specification version 4.3</title>
-<author initials="P" surname="Deutsch" fullname="L. Peter Deutsch"></author>
-</front>
-<seriesInfo name="RFC" value="1952" />
-</reference>
-
-<reference anchor="FIPS180">
-<front>
-<title>Secure Hash Standard</title>
-<author>
-<organization>National Institute of Standards and Technology</organization>
-</author>
-<date month="May" year="1993"/>
-</front>
-</reference>
-
-<reference anchor="BZ2">
-<front>
-<title>libbz2 and bzip2</title>
-<author initials="J" surname="Seward" fullname="Julian Seward" />
-</front>
-</reference>
-
-
-</references>
-
-<references title="Informative References">
-<reference anchor="libvorbis">
-<front>
-<title>libvorbis: Available from the Xiph website, http://www.xiph.org</title>
-</front>
-</reference>
-
-<reference anchor="vorbis-spec-ref">
-<front>
-<title>Ogg Vorbis I specification: Codec setup and packet decode. Available from the Xiph website, http://www.xiph.org</title>
-</front>
-</reference>
-
-<reference anchor="v-comment">
-<front>
-<title>Ogg Vorbis I specification: Comment field and header specification. Available from the Xiph website,
-http://www.xiph.org</title>
-</front>
-</reference>
-<reference anchor="RFC3611">
-<front>
-<title>RTP Control Protocol Extended Reports (RTCP XR)</title>
-<author initials="T." surname="Friedman" fullname="T. Friedman" />
-<author initials="R." surname="Caceres" fullname="R. Caceres" />
-<author initials="A." surname="Clark" fullname="A. Clark" />
-<date year="2003" month="November"/>
-</front>
-<seriesInfo name="RFC" value="3611"/>
-</reference>
-</references>
-</back>
-</rfc>
Deleted: trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-03.txt
===================================================================
--- trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-03.txt 2006-03-20 20:15:52 UTC (rev 11040)
+++ trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-03.txt 2006-03-20 20:20:37 UTC (rev 11041)
@@ -1,875 +0,0 @@
-
-
-Network Working Group Phil Kerr
-Internet-Draft Ogg Vorbis Community
-October 27, 2003 OpenDrama
-Expires: April 27, 2003
-
-
- RTP Payload Format for Vorbis Encoded Audio
-
- <draft-kerr-avt-vorbis-rtp-03.txt>
-
-Status of this Memo
-
- This document is an Internet-Draft and is in full conformance
- with all provisions of Section 10 of RFC2026.
-
- Internet-Drafts are working documents of the Internet Engineering
- Task Force (IETF), its areas, and its working groups. Note that
- other groups may also distribute working documents as
- Internet-Drafts.
-
- Internet-Drafts are draft documents valid for a maximum of six
- months and may be updated, replaced, or obsoleted by other
- documents at any time. It is inappropriate to use Internet-
- Drafts as reference material or to cite them other than as
- "work in progress".
-
- The list of current Internet-Drafts can be accessed at
- http://www.ietf.org/ietf/1id-abstracts.txt
-
- The list of Internet-Draft Shadow Directories can be accessed at
- http://www.ietf.org/shadow.html.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (2003). All Rights Reserved.
-
-Abstract
-
- This document describes a RTP payload format for transporting
- Vorbis encoded audio. It details the RTP encapsulation mechanism
- for raw Vorbis data and details the delivery mechanisms for the
- decoder probability model, referred to as a codebook, metadata
- and other setup information.
-
- [Note to RFC Editor: All references to RFC XXXX are to be replaced
- by references to the RFC number of this memo, when published.]
-
-
-
-
-
-
-
-
-Kerr Expires April 27, 2003 [Page 1]
-
-Internet Draft draft-kerr-avt-vorbis-rtp-03.txt October 27, 2003
-
-
-Table of Contents
-
- 1. Introduction ........................................ 2
- 1.1 Terminology ......................................... 2
- 2. Payload Format ...................................... 3
- 2.1 RTP Header .......................................... 3
- 2.2 Payload Header ...................................... 4
- 2.3 Payload Data ........................................ 5
- 2.4 Example RTP Packet .................................. 5
- 3. Frame Packetizing ................................... 6
- 3.1 Example Fragmented Vorbis Packet .................... 6
- 3.2 Packet Loss ......................................... 8
- 4. Configuration Headers ............................... 8
- 4.1 RTCP Based Config Header Transmission ............... 9
- 4.2 Codebook Caching .................................... 11
- 5. Session Description ................................. 11
- 5.1 SDP Based Config Header Transmission ................ 12
- 6. IANA Considerations ................................. 13
- 7. Congestion Control .................................. 13
- 8. Security Considerations ............................. 14
- 9. Acknowledgements .................................... 14
- 10. Normative References ................................ 14
- 10.1 Informative References ................................ 15
- 11. Full Copyright Statement ............................ 15
- 11.1 IPR Statement ....................................... 15
- 12. Authors Address ..................................... 15
-
-
-1 Introduction
-
- Vorbis is a general purpose perceptual audio codec intended to allow
- maximum encoder flexibility, thus allowing it to scale competitively
- over an exceptionally wide range of bitrates. At the high
- quality/bitrate end of the scale (CD or DAT rate stereo,
- 16/24 bits), it is in the same league as MPEG-2 and MPC. Similarly,
- the 1.0 encoder can encode high-quality CD and DAT rate stereo at
- below 48k bits/sec without resampling to a lower rate. Vorbis is
- also intended for lower and higher sample rates (from 8kHz
- telephony to 192kHz digital masters) and a range of channel
- representations (monaural, polyphonic, stereo, quadraphonic, 5.1,
- ambisonic, or up to 255 discrete channels).
-
- Vorbis encoded audio is generally encapsulated within an Ogg format
- bitstream [1], which provides framing and synchronization. For the
- purposes of RTP transport, this layer is unnecessary, and so raw
- Vorbis packets are used in the payload.
-
-1.1 Terminology
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
- document are to be interpreted as described in RFC 2119 [2].
-
-
-Kerr Expires April 27, 2003 [Page 2]
-
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-
-
-2 Payload Format
-
- For RTP based transportation of Vorbis encoded audio the standard
- RTP header is followed by an 8 bit payload header, then the payload
- data. The payload header is used to signify if the following packet
- contains fragmented Vorbis data and/or the the number of whole Vorbis
- data frames. The payload data contains the raw Vorbis bitstream
- information.
-
-
-2.1 RTP Header
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
-
- The RTP header begins with an octet of fields (V, P, X, and CC) to
- support specialized RTP uses (see [4] and [5] for details). For
- Vorbis RTP, the following values are used.
-
- Version (V): 2 bits
- This field identifies the version of RTP. The version
- used by this specification is two (2).
-
- Padding (P): 1 bit
- Padding MAY be used with this payload format according to
- section 5.1 of [3].
-
- Extension (X): 1 bit
- Always set to 0, as audio silence suppression is not used by
- the Vorbis codec.
-
- CSRC count (CC): 4 bits
- The CSRC count is used in accordance with [3].
-
-
-
-
-
-
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-
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-
-
- Marker (M): 1 bit
- Set to zero. Audio silence suppression not used. This conforms
- to section 4.1 of [6].
-
- Payload Type (PT): 7 bits
- An RTP profile for a class of applications is expected to assign
- a payload type for this format, or a dynamically allocated
- payload type SHOULD be chosen which designates the payload as
- Vorbis.
-
- Sequence number: 16 bits
- The sequence number increments by one for each RTP data packet
- sent, and may be used by the receiver to detect packet loss and
- to restore packet sequence. This field is detailed further in
- [3].
-
- Timestamp: 32 bits
- A timestamp representing the sampling time of the first sample of
- the first Vorbis packet in the RTP packet. The clock frequency
- MUST be set to the sample rate of the encoded audio data and is
- conveyed out-of-band as a SDP attribute.
-
- SSRC/CSRC identifiers:
- These two fields, 32 bits each with one SSRC field and a maximum
- of 16 CSRC fields, are as defined in [3].
-
-
-2.2 Payload Header
-
- After the RTP Header section the next octet is the Payload Header.
- This octet is split into a number of bitfields detailing the format
- of the following Payload Data packets.
-
- 0 1 2 3 4 5 6 7
- +---+---+---+---+---+---+---+---+
- | C | F | R | # of packets |
- +---+---+---+---+---+---+---+---+
-
- Continuation (C): 1 bit
- Set to one if this is a continuation of a fragmented packet.
-
- Fragmented (F): 1 bit
- Set to one if the payload contains complete packets or if it
- contains the last fragment of a fragmented packet.
-
- Reserved (R): 1 bit
- Reserved, MUST be set to zero by senders, and ignored by
- receivers.
-
- The last 5 bits are the number of complete packets in this payload.
- This provides for a maximum number of 32 Vorbis packets in the
- payload. If C is set to one, this number MUST be 0.
-
-Kerr Expires April 27, 2003 [Page 4]
-
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-
-
-2.3 Payload Data
-
- Vorbis packets are unbounded in length currently. At some future
- point there will likely be a practical limit placed on packet
- length.
-
- Typical Vorbis packet sizes are from very small (2-3 bytes) to
- quite large (8-12 kilobytes). The reference implementation [11]
- typically produces packets less than ~800 bytes, except for the
- header packets which are ~4-12 kilobytes.
-
- Within a RTP context the maximum Vorbis packet SHOULD be kept below
- the MTU size, typically 1500 octets, including the RTP and payload
- headers, to avoid fragmentation. For the delivery of Vorbis audio
- using RTP the maximum size of the header block is limited to 64K.
-
- If the payload contains a single Vorbis packet or a Vorbis packet
- fragment, the Vorbis packet data follows the payload header.
-
- For payloads which consist of multiple Vorbis packets, payload data
- consists of one octet representing the packet length followed by
- the packet data for each of the Vorbis packets in the payload.
-
- The Vorbis packet length field is the length of the Vorbis data
- block minus one octet.
-
- The payload packing of the Vorbis data packets SHOULD follow the
- guidelines set-out in section 4.4 of [5] where the oldest packet
- occurs immediately after the RTP packet header.
-
- Channel mapping of the audio is in accordance with BS. 775-1
- ITU-R.
-
-
-2.4 Example RTP Packet
-
- Here is an example RTP packet containing two Vorbis packets.
-
- RTP Packet Header:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 2 |0|0| 0 |0| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp (in sample rate units) |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronisation source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
-Kerr Expires April 27, 2003 [Page 5]
-
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-
-
- Payload Data:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|1|0| # pks: 2| len | vorbis data ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | ...vorbis data... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | ... | len | next vorbis packet data... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
-
-3 Frame Packetizing
-
- Each RTP packet contains either one complete Vorbis packet, one
- Vorbis packet fragment, or an integer number of complete Vorbis
- packets (up to a max of 32 packets, since the number of packets
- is defined by a 5 bit value).
-
- Any Vorbis packet that is larger than 256 octets and less than the
- path-MTU MUST be placed in a RTP packet by itself.
-
- Any Vorbis packet that is 256 bytes or less SHOULD be bundled in the
- RTP packet with as many Vorbis packets as will fit, up to a maximum
- of 32.
-
- If a Vorbis packet will not fit within the network MTU, it SHOULD be
- fragmented. A fragmented packet has a zero in the last five bits
- of the payload header. Each fragment after the first will also set
- the Continued (C) bit to one in the payload header. The RTP packet
- containing the last fragment of the Vorbis packet will have the
- Fragmented (F) bit set to one. To maintain the correct sequence
- for fragmented packet reception the timestamp field of fragmented
- packets MUST be the same as the first packet sent, with the sequence
- number incremented as normal for the subsequent RTP packets. Path
- MTU is detailed in [9] and [10].
-
-
-
-
-3.1 Example Fragmented Vorbis Packet
-
- Here is an example fragmented Vorbis packet split over three RTP
- packets.
-
-
-
-
-
-
-
-
-
-Kerr Expires April 27, 2003 [Page 6]
-
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-
-
- Packet 1:
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1000 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|0|0| 0| len | vorbis data .. |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | ..vorbis data.. |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- In this packet the initial sequence number is 1000 and the
- timestamp is xxxxx. The number of packets field is set to 0.
-
-
- Packet 2:
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1001 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |1|0|0| 0| len | vorbis data ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | ..vorbis data.. |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- The C bit is set to 1 and the number of packets field is set to 0.
- For large Vorbis fragments there can be several of these type of
- payload packets. The maximum packet size SHOULD be no greater
- than the path MTU, including all RTP and payload headers. The
- sequence number has been incremented by one but the timestamp field
- remains the same as the initial packet.
-
-
-
-
-
-Kerr Expires April 27, 2003 [Page 7]
-
-Internet Draft draft-kerr-avt-vorbis-rtp-03.txt October 27, 2003
-
-
- Packet 3:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1002 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |1|1|0| 0| len | vorbis data .. |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | ..vorbis data.. |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- This is the last Vorbis fragment packet. The C and F bits are
- set and the packet count remains set to 0. As in the previous
- packets the timestamp remains set to the first packet in the
- sequence and the sequence number has been incremented.
-
-
-3.2 Packet Loss
-
- As there is no error correction within the Vorbis stream, packet
- loss will result in a loss of signal. Packet loss is more of an
- issue for fragmented Vorbis packets as the client will have to
- cope with the handling of the C and F flags. If we use the
- fragmented Vorbis packet example above and the first packet is
- lost the client SHOULD detect that the next packet has the packet
- count field set to 0 and the C bit is set and MUST drop it. The
- next packet, which is the final fragmented packet, SHOULD be dropped
- in the same manner, or buffered. Feedback reports on lost and
- dropped packets MUST be sent back via RTCP.
-
-
-4 Configuration Headers
-
- To decode a Vorbis stream three configuration header blocks are
- needed. The first header indicates the sample and bitrates, the
- number of channels and the version of the Vorbis encoder used.
- The second header contains the decoders probability model, or
- codebooks and the third header details stream metadata.
-
-
-
-
-
-
-Kerr Expires April 27, 2003 [Page 8]
-
-Internet Draft draft-kerr-avt-vorbis-rtp-03.txt October 27, 2003
-
-
- As the RTP stream may change certain configuration data mid-session
- there are two different methods for delivering this configuration
- data to a client, RTCP which is detailed below and SDP which is
- detailed in section 5. SDP delivery is used to set-up an initial
- state for the client application and RTCP is used to change state
- during the session. The changes may be due to different metadata
- or codebooks as well as different bitrates of the stream.
-
- Unlike other mainstream audio codecs Vorbis has no statically
- configured probability model, instead it packs all entropy decoding
- configuration, VQ and Huffman models into a self-contained codebook.
- This codebook block also requires additional identification
- information detailing the number of audio channels, bit rates and
- other information used to initialise the Vorbis stream.
-
-
-4.1 RTCP Based Header Transmission
-
- The three header data blocks are sent out-of-band as an APP defined
- RTCP message with the 4 octet name field set to VORB.
-
- Synchronizing the configuration headers to the RTP stream is
- critical. A 32 bit timestamp field is used to indicate the
- timepoint when a VORB header MUST be applied to the RTP stream.
- VORB RTCP packets SHOULD be sent just ahead of the change in the
- RTP stream. As the reception loss of the RTCP header will mean
- the RTP stream will fail to decode properly the freqency of their
- periodic retransmission SHOULD be high enough to minimize the
- stream disturbance whilst remaining under the RTCP bandwidth
- allocation.
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P| subtype | PT=APP=204 | Length |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | SSRC/CSRC |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | VORB |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Timestamp (in sample rate units) |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Vorbis Version |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Audio Sample Rate |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Bitrate Maximum |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Bitrate Nominal |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
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-
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Bitrate Minimum |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | bsz 0 | bsz 1 | Num Audio Channels |c|m|o|x|x|x|x|x|
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | Codebook length | Codebook checksum |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Codebook |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. URI string |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | Vendor string length |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Vendor string ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | User comments list length |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. User comment length / User comment |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
-
- The first Vorbis config header defines the Vorbis stream
- attributes. The Vorbis version MUST be set to zero to comply with
- this document. The fields Sample Rate, Bitrate Maximum/Nominal/
- Minimum and Num Audio Channels are set in accordance with [6] with
- the bsz fields above referring to the blocksize parameters. The
- framing bit is not used for RTP transportation and so applications
- constructing Vorbis files MUST take care to set this if required.
-
- The next 8 bits are used to indicate the presence of the two
- other Vorbis stream config headers and the size overflow header.
-
- The c flag indicates the presence of a codebook header block, the
- m flag indicates the presence of a comment metadata block. The o
- flag indicates if the size of either of the c and m headers would
- make the VORB packet greater than that allowed for a RTCP message.
-
- The remaining five bits, indicated with an x, are reserved/unused
- and MUST be set to 0 for this version of the document.
-
- If the c flag is set then the next header block will contain the
- codebook configuration data.
-
- The configuration information detailed above MUST be completely
- intact, as a client can not decode a stream with an incomplete
- or corrupted codebook set.
-
- A 16 bit codebook length field and a 16 bit 1's complement checksum
- of the codebook precedes the codebook datablock. The length field
- allows for codebooks to be up to 64K in size. The checksum is used
- to detect a corrupted codebook.
-
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-
-
- If a checksum failure is detected then a new config header file
- SHOULD be obtained from SDP, if the codebook has not changed since
- the session has started. If no SDP value is set and no other method
- for obtaining the config headers exists then this is considered to
- be a failure and SHOULD be reported to the client application.
-
- If the m flag is set then the next header block will contain the
- comment metadata, such as artist name, track title and so on. These
- metadata messages are not intended to be fully descriptive but to
- offer basic track/song information. This message MUST be sent at
- the start of the stream, together with the setup and codebook
- headers, even if it contains no information. During a session the
- metadata associated with the stream may change from that specified
- at the start, e.g. a live concert broadcast changing acts/scenes, so
- clients MUST have the ability to receive m header blocks. Details
- on the format of the comments can be found in the Vorbis
- documentation [7].
-
- The format for the data takes the form of a 32 bit codec vendors
- name length field followed by the name encoded in UTF-8. The next
- field denotes the number of user comments and then the user comments
- length and text field pairs, up to the number indicated by the user
- comment list length.
-
- If the o, overflow, bit is set then the URI of a whole header block
- is specified in an overflow URI field, which is a null terminated
- UTF-8 string. The header file specified at the URI MUST NOT have
- the overflow flag set, otherwise a loop condition will occur.
-
-
-4.2 Codebook Caching
-
- Codebook caching allows clients that have previously connected to a
- stream to re-use the codebooks and thus begin the playback of the
- session faster. When a client receives a codebook it may store
- it, together with the MD5 key, locally and can compare the MD5 key
- of locally cached codebooks with the key it receives via SDP, which
- is detailed in section 5.
-
-
-5 Session Description for Vorbis RTP Streams
-
- Session description information concerning the Vorbis stream
- SHOULD be provided if possible and MUST be in accordance with [8].
- The SDP information is split into two sections, a mandatory
- section detailing the RTP stream and an optional section used to
- convey information needed for codebook caching.
-
-
-
-
-
-
-Kerr Expires April 27, 2003 [Page 11]
-
-Internet Draft draft-kerr-avt-vorbis-rtp-03.txt October 27, 2003
-
-
- Below is an outline of the mandatory SDP attributes.
-
- c=IN IP4/6 <Vorbis stream>
- m=audio <port> RTP/AVP 98
- a=rtpmap:98 vorbis/<sample rate>
- a=fmtp:98 header=<URI of Vorbis codebooks>
- a=fmtp:98 md5key=<MD5 key of codebook>
-
- The port value is specified by the server application bound to
- the address specified in the c attribute. The bitrate value
- specified in the a attribute MUST match the Vorbis sample rate
- value.
-
- The Vorbis codebook specified in the header attribute MUST contain
- all of the configuration data. If the codebook MD5 attribute,
- md5key, is set the key is compared to a locally held cache and
- if found the associated local codebook is used, if not the
- client MUST use the configuration headers specified with the
- header attribute.
-
-5.1 SDP Based Config Header Transmission
-
- The optional SDP attributes are used to convey details of the
- Vorbis stream which are required for codebook caching. If the
- following attributes are set they take precedent over values
- specified in the u attribute detailed above. The maximum size
- of the mandatory and optional SDP attributes MUST be less than
- 1K in size to conform to section 4.1 of [8].
-
- a=fmtp:98 bitrate_min=<Bitrate Minimum>
- a=fmtp:98 bitrate_norm=<Bitrate Normal>
- a=fmtp:98 bitrate_max=<Bitrate Maximum>
- a=fmtp:98 bsz0=<Block Size 0>
- a=fmtp:98 bsz1=<Block Size 1>
- a=fmtp:98 channels=<Num Audio Channels>
- a=fmtp:98 meta_vendor=<Vendor Name>
-
-
- The metadata attribute, meta_vendor, provides the bare minimum
- information required for decoding but does not convey any
- meaningful stream metadata information. As outlined in the Vorbis
- comment field and header specification documentation, [7], a number
- of predefined field names are available which SHOULD be used. An
- example would be:
-
-
-
-
-Kerr Expires April 27, 2003 [Page 12]
-
-Internet Draft draft-kerr-avt-vorbis-rtp-03.txt October 27, 2003
-
-
- a=fmtp:98 meta_vendor=Xiph.Org libVorbis I 20020717
- a=fmtp:98 meta_artist=Honest Bob and the Factory-to-Dealer-Incentives
- a=fmtp:98 meta_title=I'm Still Around
- a=fmtp:98 meta_tracknumber=5
-
-
-6 IANA Considerations
-
- MIME media type name: audio
-
- MIME subtype: vorbis
-
- Required Parameters:
- header indicates the URI of the decoding codebook.
- md5key indicates the MD5 key of the codebooks.
-
- Optional Parameters:
- bitrate_min, bitrate_norm and bitrate_max indicate the
- minimum, nominal and maximum bitrates. bsz0 and bsz1
- indicate the blocksize values. channels indicates the
- number of audio channels in the stream. meta_vendor
- indicates the encoding codec vendor.
-
- Encoding considerations:
- This type is only defined for transfer via RTP as specified
- in RFC XXXX.
-
- Security Considerations:
- See Section 6 of RFC 3047.
-
- Interoperability considerations: none
-
- Published specification:
- See the Vorbis documentation [2] for details.
-
- Applications which use this media type:
- Audio streaming and conferencing tools
-
- Additional information: none
-
- Person & email address to contact for further information:
- Phil Kerr
- philkerr at elec.gla.ac.uk/phil at plus24.com
-
- Intended usage: COMMON
-
- Author/Change controller:
- Author: Phil Kerr
- Change controller: IETF AVT Working Group
-
-7 Congestion Control
-
- Vorbis clients SHOULD send regular receiver reports detailing
- congestion. A mechanism for dynamically downgrading the stream,
- known as bitrate peeling, will allow for a graceful backing off
- of the stream bitrate. This feature is not available at present
- so an alternative would be to redirect the client to a lower
- bitrate stream if one is available.
-
-Kerr Expires April 27, 2003 [Page 13]
-
-Internet Draft draft-kerr-avt-vorbis-rtp-03.txt October 27, 2003
-
-
-8 Security Considerations
-
- RTP packets using this payload format are subject to the security
- considerations discussed in the RTP specification [3]. This implies
- that the confidentiality of the media stream is achieved by using
- encryption. Because the data compression used with this payload
- format is applied end-to-end, encryption may be performed on the
- compressed data. Where the size of a data block is set care MUST
- be taken to prevent buffer overflows in the client applications.
-
-
-9 Acknowledgments
-
- This document is a continuation of draft-moffitt-vorbis-rtp-00.txt.
- The MIME type section is a continuation of draft-short-avt-rtp-
- vorbis-mime-00.txt
-
- Thanks to the AVT, Ogg Vorbis Communities / Xiph.org including
- Steve Casner, Ramon Garcia, Pascal Hennequin, Ralph Jiles,
- Tor-Einar Jarnbjo, Colin Law, John Lazzaro, Jack Moffitt,
- Colin Perkins, Barry Short, Mike Smith, Magnus Westerlund.
-
-
-10 Normative References
-
- 1. The Ogg Encapsulation Format Version 0 (RFC 3533), S. Pfeiffer.
-
- 2. Key words for use in RFCs to Indicate Requirement Levels
- (RFC 2119), S. Bradner.
-
- 3. RTP: A Transport Protocol for Real-Time Applications (RFC 1889),
- Schulzrinne, et al.
-
- 4. RTP: A transport protocol for real-time applications. Work
- in progress, draft-ietf-avt-rtp-new-11.txt.
-
- 5. RTP Profile for Audio and Video Conferences with Minimal Control.
- Work in progress, draft-ietf-avt-profile-new-12.txt.
-
- 6. Ogg Vorbis I spec: Codec setup and packet decode.
- http://www.xiph.org/ogg/vorbis/doc/vorbis-spec-ref.html
-
- 7. Ogg Vorbis I spec: Comment field and header specification.
- http://www.xiph.org/ogg/vorbis/doc/v-comment.html
-
- 8. SDP: Session Description Protocol (RFC 2327), Handley, M. and
- V. Jacobson.
-
- 9. Path MTU Discovery (RFC 1063), Mogul & Deering
-
- 10. Path MTU Discovery for IP version 6 (RFC 1981), McCann, J. et al.
-
-
-
-
-
-Kerr Expires April 27, 2003 [Page 14]
-
-Internet Draft draft-kerr-avt-vorbis-rtp-03.txt October 27, 2003
-
-
-10.1 Informative References
-
- 11. libvorbis: Available from the Xiph website, http://www.xiph.org
-
-
-11 Full Copyright Statement
-
- Copyright (C) The Internet Society (2003). All Rights Reserved.
-
- This document and translations of it may be copied and furnished to
- others, and derivative works that comment on or otherwise explain it
- or assist in its implementation may be prepared, copied, published
- and distributed, in whole or in part, without restriction of any
- kind, provided that the above copyright notice and this paragraph are
- included on all such copies and derivative works. However, this
- document itself may not be modified in any way, such as by removing
- the copyright notice or references to the Internet Society or other
- Internet organizations, except as needed for the purpose of
- developing Internet standards in which case the procedures for
- copyrights defined in the Internet Standards process must be
- followed, or as required to translate it into languages other than
- English.
-
- The limited permissions granted above are perpetual and will not be
- revoked by the Internet Society or its successors or assigns.
-
- This document and the information contained herein is provided on an
- "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
- TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
- BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
- HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
- MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-10.1 IPR Statement
-
- "The IETF takes no position regarding the validity or scope of
any intellectual property or other rights that might be claimed
to pertain to the implementation or use of the technology
described in this document or the extent to which any license
under such rights might or might not be available; neither does
it represent that it has made any effort to identify any such
rights. Information on the IETF's procedures with respect to
rights in standards-track and standards-related documentation
can be found in BCP-11. Copies of claims of rights made
available for publication and any assurances of licenses to
be made available, or the result of an attempt made
to obtain a general license or permission for the use of such
proprietary rights by implementors or users of this
specification can be obtained from the IETF Secretariat."
-
- Further IPR details on the Vorbis bitstream may be found on the
- Xiph website: http://www.xiph.org
-
-
-
-12 Authors Address
-
- Phil Kerr
- Centre for Music Technology
- University of Glasgow
- Glasgow, Scotland
- UK, G12 8LT
- Phone: +44 141 330 5740
- Email: philkerr at elec.gla.ac.uk
- phil at plus24.com
-
- WWW: http://www.xiph.org/
-
-
-Kerr Expires April 27, 2003 [Page 15]
-
Deleted: trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-04.xml
===================================================================
--- trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-04.xml 2006-03-20 20:15:52 UTC (rev 11040)
+++ trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-04.xml 2006-03-20 20:20:37 UTC (rev 11041)
@@ -1,928 +0,0 @@
-<?xml version='1.0'?>
-<!DOCTYPE rfc SYSTEM 'rfc2629.dtd'>
-<?rfc toc="yes" ?>
-
-<rfc ipr="full3667" docName="RTP Payload Format for Vorbis Encoded Audio">
-
-<front>
-<title>draft-kerr-avt-vorbis-rtp-04</title>
-
-<author initials="P" surname="Kerr" fullname="Phil Kerr">
-<organization>Xiph.Org</organization>
-<address>
-<email>phil at plus24.com</email>
-<uri>http://www.xiph.org/</uri>
-</address>
-</author>
-
-<date day="31" month="December" year="2004" />
-
-<area>General</area>
-<workgroup>AVT Working Group</workgroup>
-<keyword>I-D</keyword>
-
-<keyword>Internet-Draft</keyword>
-<keyword>Vorbis</keyword>
-<keyword>RTP</keyword>
-
-<abstract>
-<t>This document describes a RTP payload format for transporting
-Vorbis encoded audio. It details the RTP encapsulation mechanism
-for raw Vorbis data and details the delivery mechanisms for the
-decoder probability model, referred to as a codebook, metadata
-and other setup information.</t>
-</abstract>
-
-<note title="Editors Note">
-<t>
-All references to RFC XXXX are to be replaced by references to the RFC number of this memo, when published.
-</t>
-</note>
-
-</front>
-
-<middle>
-
-<section anchor="Introduction" title="Introduction">
-<t>
-Vorbis is a general purpose perceptual audio codec intended to allow
-maximum encoder flexibility, thus allowing it to scale competitively
-over an exceptionally wide range of bitrates. At the high
-quality/bitrate end of the scale (CD or DAT rate stereo,
-16/24 bits), it is in the same league as MPEG-2 and MPC. Similarly,
-the 1.0 encoder can encode high-quality CD and DAT rate stereo at
-below 48k bits/sec without resampling to a lower rate. Vorbis is
-also intended for lower and higher sample rates (from 8kHz
-telephony to 192kHz digital masters) and a range of channel
-representations (monaural, polyphonic, stereo, quadraphonic, 5.1,
-ambisonic, or up to 255 discrete channels).
-
-Vorbis encoded audio is generally encapsulated within an Ogg format
-bitstream <xref target="rfc3533"></xref>, which provides framing and synchronization. For the
-purposes of RTP transport, this layer is unnecessary, and so raw
-Vorbis packets are used in the payload.
-</t>
-
-<section anchor="Terminology" title="Terminology">
-
-<t>
-The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-document are to be interpreted as described in RFC 2119 <xref target="rfc2119"></xref>.
-</t>
-
-</section>
-</section>
-
-<section anchor="Payload Format" title="Payload Format">
-<t>
-For RTP based transportation of Vorbis encoded audio the standard
-RTP header is followed by a 5 octet payload header, then the payload
-data. The payload headers are used to associate the Vorbis data with
-its associated decoding codebooks as well as indicating if the following packet
-contains fragmented Vorbis data and/or the the number of whole Vorbis
-data frames. The payload data contains the raw Vorbis bitstream
-information.
-</t>
-
-<section anchor="RTP Header" title="RTP Header">
-
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-
-<t>
-The RTP header begins with an octet of fields (V, P, X, and CC) to
-support specialized RTP uses (see <xref target="rfc3550"></xref> and <xref target="rfc3551"></xref> for details). For Vorbis RTP, the following values are used.
-</t>
-
-<t>
-Version (V): 2 bits</t><t>
-This field identifies the version of RTP. The version
-used by this specification is two (2).
-</t>
-
-<t>
-Padding (P): 1 bit</t><t>
-Padding MAY be used with this payload format according to
-section 5.1 of <xref target="rfc3550"></xref>.
-</t>
-
-<t>
-Extension (X): 1 bit</t><t>
-Always set to 0, as audio silence suppression is not used by
-the Vorbis codec.
-</t>
-
-<t>
-CSRC count (CC): 4 bits</t><t>
-The CSRC count is used in accordance with <xref target="rfc3550"></xref>.
-</t>
-
-<t>
-Marker (M): 1 bit</t><t>
-Set to zero. Audio silence suppression not used. This conforms
-to section 4.1 of <xref target="vorbis-spec-ref"></xref>.
-</t>
-
-<t>
-Payload Type (PT): 7 bits</t><t>
-An RTP profile for a class of applications is expected to assign
-a payload type for this format, or a dynamically allocated
-payload type SHOULD be chosen which designates the payload as
-Vorbis.
-</t>
-
-<t>
-Sequence number: 16 bits</t><t>
-The sequence number increments by one for each RTP data packet
-sent, and may be used by the receiver to detect packet loss and
-to restore packet sequence. This field is detailed further in
-<xref target="rfc3550"></xref>.
-</t>
-
-<t>
-Timestamp: 32 bits</t><t>
-A timestamp representing the sampling time of the first sample of
-the first Vorbis packet in the RTP packet. The clock frequency
-MUST be set to the sample rate of the encoded audio data and is
-conveyed out-of-band as a SDP attribute.
-</t>
-
-<t>
-SSRC/CSRC identifiers: </t><t>
-These two fields, 32 bits each with one SSRC field and a maximum
-of 16 CSRC fields, are as defined in <xref target="rfc3550"></xref>.
-</t>
-
-</section>
-
-<section anchor="Payload Header" title="Payload Header">
-
-<t>
-After the RTP Header section the following five octets are the Payload Header.
-This header is split into a number of bitfields detailing the format
-of the following Payload Data packets.
-</t>
-
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |C|F| T |# pkts.|
- +-+-+-+-+-+-+-+-+
-]]></artwork>
-
-<t>
-Codebook Ident: 32 bits</t><t>
-This 32 bit field is used to associate the Vorbis data to a decoding Codebook.
-It is created by making a CRC32 checksum of the codebook required to decode the
-particular Vorbis audio stream.
-</t>
-
-<t>
-Continuation (C): 1 bit</t><t>
-Set to one if this is a continuation of a fragmented packet.
-</t>
-
-<t>
-Fragmented (F): 1 bit</t><t>
-Set to one if the payload contains complete packets or if it
-contains the last fragment of a fragmented packet.
-</t>
-
-<t>
-Payload Type (T): 2 bits</t><t>
-This field sets the packet payload type. There are currently four type of packet payloads.
-</t>
-
-<vspace blankLines="1" />
-<list style="empty">
-<t> 0 = Raw Vorbis payload</t>
-<t> 1 = Configuration payload</t>
-<t> 2 = Codebook payload</t>
-<t> 3 = Metadata payload</t>
-</list>
-
-<t>
-The last 4 bits are the number of complete packets in this payload.
-This provides for a maximum number of 15 Vorbis packets in the
-payload. If the packet contains fragmented data the number of packets MUST be set to 0.
-</t>
-
-</section>
-
-<section anchor="Payload Data" title="Payload Data">
-
-<t>
-Raw Vorbis packets are unbounded in length currently, although at some future
-point there will likely be a practical limit placed on them.
-Typical Vorbis packet sizes are from very small (2-3 bytes) to
-quite large (8-12 kilobytes). The reference implementation <xref target="libvorbis"></xref>
-typically produces packets less than ~800 bytes, except for the
-codebook header packets which are ~4-12 kilobytes.
-Within an RTP context the maximum Vorbis packet size, including the RTP and payload
-headers, SHOULD be kept below the path MTU to avoid packet fragmentation.
-</t>
-
-<t>
-Each Vorbis payload packet starts with a one octet length header,
-which is used to represent the size of the following data payload, followed
-by the raw Vorbis data.
-</t>
-
-<t>
-For payloads which consist of multiple Vorbis packets the payload data
-consists of the packet length followed by the packet data for each of
-the Vorbis packets in the payload.
-</t>
-
-<t>
-The Vorbis packet length header is the length of the Vorbis data
-block only and does not count the length octet.
-</t>
-
-<t>
-The payload packing of the Vorbis data packets SHOULD follow the
-guidelines set-out in <xref target="rfc3551"></xref> where the oldest packet
-occurs immediately after the RTP packet header.
-</t>
-
-<t>
-Channel mapping of the audio is in accordance with BS. 775-1
-ITU-R.
-</t>
-
-</section>
-
-<section anchor="Example RTP Packet" title="Example RTP Packet">
-
-<t>
-Here is an example RTP packet containing two Vorbis packets.
-</t>
-<t>
-RTP Packet Header:
-</t>
-
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 2 |0|0| 0 |0| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp (in sample rate units) |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronisation source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-
-<t>
-Payload Data:
-</t>
-
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|1| 0 | 2 pks | len | vorbis data ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. ...vorbis data... ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. data | len | next vorbis packet data... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-
-</section>
-
-</section>
-
-<section anchor="Frame Packetizing" title="Frame Packetizing">
-
-<t>
-Each RTP packet contains either one complete Vorbis packet, one
-Vorbis packet fragment, or an integer number of complete Vorbis
-packets (up to a max of 15 packets, since the number of packets
-is defined by a 4 bit value).
-</t>
-
-<t>
-Any Vorbis data packet that is 256 octets or less SHOULD be bundled in the
-RTP packet with as many Vorbis packets as will fit, up to a maximum
-of 15.
-</t>
-
-<t>
-If a Vorbis packet is larger than 256 octets it MUST be
-fragmented. A fragmented packet has a zero in the last four bits
-of the payload header. Each fragment after the first will also set
-the Continued (C) bit to one in the payload header. The RTP packet
-containing the last fragment of the Vorbis packet will have the
-Fragmented (F) bit set to one. To maintain the correct sequence
-for fragmented packet reception the timestamp field of fragmented
-packets MUST be the same as the first packet sent, with the sequence
-number incremented as normal for the subsequent RTP packets. Path
-MTU is detailed in <xref target="rfc1063"></xref> and <xref target="rfc1981"></xref>.
-</t>
-
-<section anchor="Example Fragmented Vorbis Packet" title="Example Fragmented Vorbis Packet">
-
-<t>
-Here is an example fragmented Vorbis packet split over three RTP
-packets.
-</t>
-
-<artwork><![CDATA[
- Packet 1:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1000 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|0| 0 | 0| len | vorbis data .. |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | ..vorbis data.. |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-
-<t>
-In this packet the initial sequence number is 1000 and the
-timestamp is xxxxx. The number of packets field is set to 0.
-</t>
-
-<artwork><![CDATA[
- Packet 2:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1001 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |1|0| 0 | 0| len | vorbis data ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | ..vorbis data.. |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-
-<t>
-The C bit is set to 1 and the number of packets field is set to 0.
-For large Vorbis fragments there can be several of these type of
-payload packets. The maximum packet size SHOULD be no greater
-than the path MTU, including all RTP and payload headers. The
-sequence number has been incremented by one but the timestamp field
-remains the same as the initial packet.
-</t>
-
-<artwork><![CDATA[
- Packet 3:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1002 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |1|1| 0 | 0| len | vorbis data .. |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | ..vorbis data.. |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-
-<t>
-This is the last Vorbis fragment packet. The C and F bits are
-set and the packet count remains set to 0. As in the previous
-packets the timestamp remains set to the first packet in the
-sequence and the sequence number has been incremented.
-</t>
-</section>
-
-<section anchor="Packet Loss" title="Packet Loss">
-
-<t>
-As there is no error correction within the Vorbis stream, packet
-loss will result in a loss of signal. Packet loss is more of an
-issue for fragmented Vorbis packets as the client will have to
-cope with the handling of the C and F flags. If we use the
-fragmented Vorbis packet example above and the first packet is
-lost the client SHOULD detect that the next packet has the packet
-count field set to 0 and the C bit is set and MUST drop it. The
-next packet, which is the final fragmented packet, SHOULD be dropped
-in the same manner, or buffered. Feedback reports on lost and
-dropped packets MUST be sent back via RTCP.
-</t>
-
-</section>
-
-</section>
-
-<section anchor="Configuration Headers" title="Configuration Headers">
-
-<t>
-Unlike other mainstream audio codecs Vorbis has no statically
-configured probability model, instead it packs all entropy decoding
-configuration, VQ and Huffman models into a self-contained codebook.
-This codebook block also requires additional identification
-information detailing the number of audio channels, bitrates and
-other information used to initialise the Vorbis stream.
-</t>
-
-<t>
-To decode a Vorbis stream three configuration header blocks are
-needed. The first header indicates the sample and bitrates, the
-number of channels and the version of the Vorbis encoder used.
-The second header contains the decoders probability model, or
-codebook and the third header details stream metadata.
-</t>
-
-<t>
-As the RTP stream may change certain configuration data mid-session
-there are two different methods for delivering this configuration
-data to a client, in-band and SDP which is
-detailed below. SDP delivery is used to set-up an initial
-state for the client application and in-band is used to change state
-during the session. The changes may be due to different metadata
-or codebooks as well as different bitrates of the stream.
-</t>
-
-<t>
-Out of the two delivery vectors the use of an SDP attribute to indicate an URI
-where the configuration and codebook data can be obtained is preferred
-as they can be fetched reliably using TCP. The in-band codebook delivery SHOULD
-only be used in situations where the link between the client is unidirectional or if
-the SDP-based information is not available.
-</t>
-
-<t>
-Synchronizing the configuration and codebook headers to the RTP stream is
-critical. The 32 bit Codebook Ident field is used to indicate when a change in the stream has
-taken place. The client application MUST have in advance the correct configuration and codebook
-headers and if the client detects a change in the Ident value and does not have this information
-it MUST NOT decode the raw Vorbis data.
-</t>
-
-<section anchor="In-band Header Transmission" title="In-band Header Transmission">
-
-<t>
-The three header data blocks are sent in-band with the packet type bits set to
-match the payload type. Normally the codebook and configuration
-headers are sent once per session if the stream is an encoding of live audio, as typically
-the encoder state will not change, but the encoder state can change at the boundary
-of chained Vorbis audio files. Metadata can be sent at the start as well as any time during
-the life of the session. Clients MUST be capable of dealing with periodic re-transmission of the
-configuration headers.
-</t>
-
-<t>
-A Vorbis configuration header is indicated with the payload type field set to 1.
-The Vorbis version MUST be set to zero to comply with
-this document. The fields Sample Rate, Bitrate Maximum/Nominal/
-Minimum and Num Audio Channels are set in accordance with <xref target="vorbis-spec-ref"></xref> with
-the bsz fields above referring to the blocksize parameters. The
-framing bit is not used for RTP transportation and so applications
-constructing Vorbis files MUST take care to set this if required.
-</t>
-
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | xxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|1| 2 | 1| bsz 0 | bsz 1 | Num Audio Channels |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Vorbis Version |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Audio Sample Rate |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Bitrate Maximum |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Bitrate Nominal |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Bitrate Minimum |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-
-<t>
-If the payload type field is set to 2, this indicates the packet contains codebook data.
-</t>
-
-<t>
-The configuration information detailed below MUST be completely
-intact, as a client can not decode a stream with an incomplete
-or corrupted codebook set.
-</t>
-
-<t>
-A 16 bit codebook length field precedes the codebook datablock. The length field
-allows for codebooks to be up to 64K in size. Packet fragmentation,
-as per the Vorbis data, MUST be performed if the codebooks size exceeds
-path MTU. The Codebook Ident field MUST be set to match the associated codebook
-needed to decode the Vorbis stream.
-</t>
-
-<t>
-The Codebook Ident is the CRC32 checksum of the codebook and
-is used to detect a corrupted codebook as well as
-associating it with its Vorbis data stream. This Ident value
-MUST NOT be set to the value of the current stream if this header is
-being sent before the boundary of the chained file has been reached.
-If a checksum failure is detected then this is considered to
-be a failure and MUST be reported to the client application.
-</t>
-
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | xxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|1| 2 | 1| Codebook Length |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | Codebook ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Codebook |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-
-
-<t>
-With the payload type flag set to 3, this indicates that the packet contain the
-comment metadata, such as artist name, track title and so on. These
-metadata messages are not intended to be fully descriptive but to
-offer basic track/song information. This message MUST be sent at
-the start of the stream, together with the setup and codebook
-headers, even if it contains no information. During a session the
-metadata associated with the stream may change from that specified
-at the start, e.g. a live concert broadcast changing acts/scenes, so
-clients MUST have the ability to receive header blocks. Details
-on the format of the comments can be found in the Vorbis
-documentation <xref target="v-comment"></xref>.
-</t>
-
-
- 1) [vendor_length] = read an unsigned integer of 32 bits
- 2) [vendor_string] = read a UTF-8 vector as [vendor_length] octets
- 3) [user_comment_list_length] = read an unsigned integer of 32 bits
- 4) iterate [user_comment_list_length] times {
-
- 5) [length] = read an unsigned integer of 32 bits
- 6) this iteration's user comment = read a UTF-8 vector as [length] octets
-
- }
-
- 7) [framing_bit] = read a single bit as boolean
- 8) if ( [framing_bit] unset or end of packet ) then ERROR
- 9) done.
-
-
-<t>
-The format for the data takes the form of a 32 bit codec vendors
-name length field followed by the name encoded in UTF-8. The next 32
-bit field denotes the number of user comments. Each of the user comments
-is prefixed by a 32 bit length field followed by the comment text.
-</t>
-
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | xxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|1| 3 | 1| Vendor string length |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | Vendor string ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | User comments list length |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. User comment length / User comment |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-
-</section>
-
-<section anchor="Session Description for Vorbis RTP Streams" title="Session Description for Vorbis RTP Streams">
-<t>
-Session description information concerning the Vorbis stream
-SHOULD be provided if possible and MUST be in accordance with <xref target="rfc2327"></xref>.
-</t>
-
-<t>
-If the stream comprises chained Vorbis files the configuration and codebook headers for each
-file SHOULD be packaged together and passed to the client using the headers attribute.
-</t>
-
-<t>
-Below is an outline of the mandatory SDP attributes.
-</t>
-
-<vspace blankLines="1" />
-<list style="empty">
-<t>c=IN IP4/6 </t>
-<t>m=audio RTP/AVP 98</t>
-<t>a=rtpmap:98 VORBIS/44100/2</t>
-<t>a=fmtp:98 header=<URI of configuration header> </t>
-</list>
-
-<t>
-The Vorbis configuration specified in the header attribute MUST contain
-all of the configuration data and codebooks needed for the life of the session.
-</t>
-
-<t>
-The port value is specified by the server application bound to
-the address specified in the c attribute. The bitrate value
-and channels specified in the m attribute MUST match the Vorbis
-sample rate value.
-</t>
-
-</section>
-
-<section anchor="Codebook Caching" title="Codebook Caching">
-
-<t>
-Codebook caching allows clients that have previously connected to a
-stream to re-use the associated codebooks and configuration data.
-When a client receives a codebook it may store it locally and can
-compare the CRC32 key with that of the new stream and begin decoding
-before it has received any of the headers.
-</t>
-
-</section>
-
-</section>
-
-<section anchor="IANA Considerations" title="IANA Considerations">
-
-<t>
-MIME media type name: audio
-</t>
-<t>
-MIME subtype: vorbis
-</t>
-
-<t>
-Required Parameters:</t><t>
-header indicates the URI of the decoding configuration headers.
-</t>
-
-<t>
-Optional Parameters: </t><t>
-None.
-</t>
-
-<t>
-Encoding considerations:</t><t>
-This type is only defined for transfer via RTP as specified
-in RFC XXXX.
-</t>
-
-<t>
-Security Considerations:</t><t>
-See Section 6 of RFC 3047.
-</t>
-
-<t>
-Interoperability considerations: none
-</t>
-
-<t>
-Published specification:</t>
-<t>See the Vorbis documentation <xref target="vorbis-spec-ref"></xref> for details.</t>
-
-<t>
-Applications which use this media type:</t><t>
-Audio streaming and conferencing tools
-</t>
-
-<t>
-Additional information: none
-</t>
-
-<t>
-Person & email address to contact for further information:</t><t>
-Phil Kerr: <phil at plus24.com>
-</t>
-
-<t>
-Intended usage: COMMON
-</t>
-
-<t>
-Author/Change controller:</t><t>
-Author: Phil Kerr
-Change controller: IETF AVT Working Group
-</t>
-
-</section>
-
-<section anchor="Congestion Control" title="Congestion Control">
-
-<t>
-Vorbis clients SHOULD send regular receiver reports detailing
-congestion. A mechanism for dynamically downgrading the stream,
-known as bitrate peeling, will allow for a graceful backing off
-of the stream bitrate. This feature is not available at present
-so an alternative would be to redirect the client to a lower
-bitrate stream if one is available.
-</t>
-
-</section>
-
-<section anchor="Security Considerations" title="Security Considerations">
-<t>
-RTP packets using this payload format are subject to the security
-considerations discussed in the RTP specification <xref target="rfc3550"></xref>. This implies
-that the confidentiality of the media stream is achieved by using
-encryption. Because the data compression used with this payload
-format is applied end-to-end, encryption may be performed on the
-compressed data. Where the size of a data block is set care MUST
-be taken to prevent buffer overflows in the client applications.
-</t>
-
-</section>
-
-<section anchor="Acknowledgments" title="Acknowledgments">
-
-<t>
-This document is a continuation of draft-moffitt-vorbis-rtp-00.txt.
-The MIME type section is a continuation of draft-short-avt-rtp-
-vorbis-mime-00.txt
-</t>
-
-<t>
-Thanks to the AVT, Ogg Vorbis Communities / Xiph.org including
-Steve Casner, Aaron Colwell, Ross Finlayson, Ramon Garcia, Pascal Hennequin, Ralph Giles,
-Tor-Einar Jarnbjo, Colin Law, John Lazzaro, Jack Moffitt, Christopher Montgomery,
-Colin Perkins, Barry Short, Mike Smith, Magnus Westerlund.
-</t>
-
-</section>
-
-</middle>
-
-<back>
-
-<references title="Normative References">
-
-<reference anchor="rfc3533">
-<front>
-<title>The Ogg Encapsulation Format Version 0</title>
-<author initials="S." surname="Pfeiffer" fullname="Silvia Pfeiffer"></author>
-</front>
-<seriesInfo name="RFC" value="3533" />
-</reference>
-
-<reference anchor="rfc2119">
-<front>
-<title>Key words for use in RFCs to Indicate Requirement Levels </title>
-<author initials="S." surname="Bradner" fullname="Scott Bradner"></author>
-</front>
-<seriesInfo name="RFC" value="2119" />
-</reference>
-
-<reference anchor="rfc3550">
-<front>
-<title>RTP: A Transport Protocol for real-time applications</title>
-<author initials="H." surname="Schulzrinne" fullname=""></author>
-<author initials="S." surname="Casner" fullname=""></author>
-<author initials="R." surname="Frederick" fullname=""></author>
-<author initials="V." surname="Jacobson" fullname=""></author>
-</front>
-<seriesInfo name="RFC" value="3550" />
-</reference>
-
-<reference anchor="rfc3551">
-<front>
-<title>RTP Profile for Audio and Video Conferences with Minimal Control.</title>
-<author initials="H." surname="Schulzrinne" fullname=""></author>
-<author initials="S." surname="Casner" fullname=""></author>
-</front>
-<date month="July" year="2003" />
-<seriesInfo name="RFC" value="3551" />
-</reference>
-
-<reference anchor="rfc2327">
-<front>
-<title>SDP: Session Description Protocol</title>
-<author initials="M." surname="Handley" fullname="Mark Handley"></author>
-<author initials="V." surname="Jacobson" fullname="Van Jacobson"></author>
-</front>
-<seriesInfo name="RFC" value="2327" />
-</reference>
-
-<reference anchor="rfc1063">
-<front>
-<title>Path MTU Discovery</title>
-<author initials="J." surname="Mogul et al." fullname="J. Mogul et al."></author>
-</front>
-<seriesInfo name="RFC" value="1063" />
-</reference>
-
-<reference anchor="rfc1981">
-<front>
-<title>Path MTU Discovery for IP version 6</title>
-<author initials="J." surname="McCann et al." fullname="J. McCann et al."></author>
-</front>
-<seriesInfo name="RFC" value="1981" />
-</reference>
-</references>
-
-<references title="Informative References">
-<reference anchor="libvorbis">
-<front>
-<title>libvorbis: Available from the Xiph website, http://www.xiph.org</title>
-</front>
-</reference>
-
-<reference anchor="vorbis-spec-ref">
-<front>
-<title>Ogg Vorbis I spec: Codec setup and packet decode. http://www.xiph.org/ogg/vorbis/doc/vorbis-spec-ref.html</title>
-</front>
-</reference>
-
-<reference anchor="v-comment">
-<front>
-<title>Ogg Vorbis I spec: Comment field and header specification. http://www.xiph.org/ogg/vorbis/doc/v-comment.html</title>
-</front>
-</reference>
-
-</references>
-</back>
-</rfc>
Deleted: trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-05.txt
===================================================================
--- trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-05.txt 2006-03-20 20:15:52 UTC (rev 11040)
+++ trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-05.txt 2006-03-20 20:20:37 UTC (rev 11041)
@@ -1,1290 +0,0 @@
-
-
-
-
-AVT Working Group L. Barbato
-Internet-Draft Xiph.Org
-Expires: April 24, 2006 October 21, 2005
-
-
- draft-kerr-avt-vorbis-rtp-05
- RTP Payload Format for Vorbis Encoded Audio
-
-Status of this Memo
-
- By submitting this Internet-Draft, each author represents that any
- applicable patent or other IPR claims of which he or she is aware
- have been or will be disclosed, and any of which he or she becomes
- aware will be disclosed, in accordance with Section 6 of BCP 79.
-
- Internet-Drafts are working documents of the Internet Engineering
- Task Force (IETF), its areas, and its working groups. Note that
- other groups may also distribute working documents as Internet-
- Drafts.
-
- Internet-Drafts are draft documents valid for a maximum of six months
- and may be updated, replaced, or obsoleted by other documents at any
- time. It is inappropriate to use Internet-Drafts as reference
- material or to cite them other than as "work in progress."
-
- The list of current Internet-Drafts can be accessed at
- http://www.ietf.org/ietf/1id-abstracts.txt.
-
- The list of Internet-Draft Shadow Directories can be accessed at
- http://www.ietf.org/shadow.html.
-
- This Internet-Draft will expire on April 24, 2006.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (2005).
-
-Abstract
-
- This document describes an RTP payload format for transporting Vorbis
- encoded audio. It details the RTP encapsulation mechanism for raw
- Vorbis data and details the delivery mechanisms for the decoder
- probability model, referred to as a codebook and other setup
- information.
-
- Also included within the document are the necessary details for the
- use of Vorbis with MIME and Session Description Protocol (SDP).
-
-
-
-
-Barbato Expires April 24, 2006 [Page 1]
-
-Internet-Draft draft-kerr-avt-vorbis-rtp-05 October 2005
-
-
-Editors Note
-
- All references to RFC XXXX are to be replaced by references to the
- RFC number of this memo, when published.
-
-
-Table of Contents
-
- 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
- 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
- 2. Payload Format . . . . . . . . . . . . . . . . . . . . . . . . 3
- 2.1. RTP Header . . . . . . . . . . . . . . . . . . . . . . . . 3
- 2.2. Payload Header . . . . . . . . . . . . . . . . . . . . . . 5
- 2.3. Payload Data . . . . . . . . . . . . . . . . . . . . . . . 6
- 2.4. Example RTP Packet . . . . . . . . . . . . . . . . . . . . 7
- 3. Configuration Headers . . . . . . . . . . . . . . . . . . . . 8
- 3.1. In-band Header Transmission . . . . . . . . . . . . . . . 9
- 3.1.1. Packed Configuration . . . . . . . . . . . . . . . . . 9
- 3.2. Out of Band Transmission . . . . . . . . . . . . . . . . . 10
- 3.2.1. Packed Headers . . . . . . . . . . . . . . . . . . . . 10
- 3.3. Loss of Configuration Headers . . . . . . . . . . . . . . 12
- 4. Comment Headers . . . . . . . . . . . . . . . . . . . . . . . 12
- 5. Frame Packetizing . . . . . . . . . . . . . . . . . . . . . . 13
- 5.1. Example Fragmented Vorbis Packet . . . . . . . . . . . . . 14
- 5.2. Packet Loss . . . . . . . . . . . . . . . . . . . . . . . 16
- 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
- 6.1. Mapping MIME Parameters into SDP . . . . . . . . . . . . . 18
- 7. Congestion Control . . . . . . . . . . . . . . . . . . . . . . 19
- 8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
- 8.1. Stream Radio . . . . . . . . . . . . . . . . . . . . . . . 19
- 9. Security Considerations . . . . . . . . . . . . . . . . . . . 20
- 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
- 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
- 11.1. Normative References . . . . . . . . . . . . . . . . . . . 21
- 11.2. Informative References . . . . . . . . . . . . . . . . . . 21
- Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 22
- Intellectual Property and Copyright Statements . . . . . . . . . . 23
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Barbato Expires April 24, 2006 [Page 2]
-
-Internet-Draft draft-kerr-avt-vorbis-rtp-05 October 2005
-
-
-1. Introduction
-
- Vorbis is a general purpose perceptual audio codec intended to allow
- maximum encoder flexibility, thus allowing it to scale competitively
- over an exceptionally wide range of bitrates. At the high quality/
- bitrate end of the scale (CD or DAT rate stereo, 16/24 bits), it is
- in the same league as MPEG-2 and MPC. Similarly, the version 1.1
- reference encoder can encode high-quality CD and DAT rate stereo at
- below 48k bits/sec without resampling to a lower rate. Vorbis is
- also intended for lower and higher sample rates (from 8kHz telephony
- to 192kHz digital masters) and a range of channel representations
- (monaural, polyphonic, stereo, quadraphonic, 5.1, ambisonic, or up to
- 255 discrete channels).
-
- Vorbis encoded audio is generally encapsulated within an Ogg format
- bitstream [1], which provides framing and synchronization. For the
- purposes of RTP transport, this layer is unnecessary, and so raw
- Vorbis packets are used in the payload.
-
-1.1. Terminology
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
- document are to be interpreted as described in RFC 2119 [2].
-
-
-2. Payload Format
-
- For RTP based transportation of Vorbis encoded audio the standard RTP
- header is followed by a 4 octet payload header, then the payload
- data. The payload headers are used to associate the Vorbis data with
- its associated decoding codebooks as well as indicating if the
- following packet contains fragmented Vorbis data and/or the the
- number of whole Vorbis data frames. The payload data contains the
- raw Vorbis bitstream information.
-
-2.1. RTP Header
-
- The format of the RTP header is specified in [3] and shown in Figure
- Figure 1. This payload format uses the fields of the header in a
- manner consistent with that specification.
-
-
-
-
-
-
-
-
-
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-
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 1: RTP Header
-
- The RTP header begins with an octet of fields (V, P, X, and CC) to
- support specialized RTP uses (see [3] and [4] for details). For
- Vorbis RTP, the following values are used.
-
- Version (V): 2 bits
-
- This field identifies the version of RTP. The version used by this
- specification is two (2).
-
- Padding (P): 1 bit
-
- Padding MAY be used with this payload format according to section 5.1
- of [3].
-
- Extension (X): 1 bit
-
- The Extension bit is used in accordance with [3].
-
- CSRC count (CC): 4 bits
-
- The CSRC count is used in accordance with [3].
-
- Marker (M): 1 bit
-
- Set to zero. Audio silence suppression not used. This conforms to
- section 4.1 of [12].
-
- Payload Type (PT): 7 bits
-
- An RTP profile for a class of applications is expected to assign a
- payload type for this format, or a dynamically allocated payload type
- SHOULD be chosen which designates the payload as Vorbis.
-
-
-
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-
-
- Sequence number: 16 bits
-
- The sequence number increments by one for each RTP data packet sent,
- and may be used by the receiver to detect packet loss and to restore
- packet sequence. This field is detailed further in [3].
-
- Timestamp: 32 bits
-
- A timestamp representing the sampling time of the first sample of the
- first Vorbis packet in the RTP packet. The clock frequency MUST be
- set to the sample rate of the encoded audio data and is conveyed out-
- of-band as a SDP attribute.
-
- SSRC/CSRC identifiers:
-
- These two fields, 32 bits each with one SSRC field and a maximum of
- 16 CSRC fields, are as defined in [3].
-
-2.2. Payload Header
-
- After the RTP Header section the following 4 octets are the Payload
- Header. This header is split into a number of bitfields detailing
- the format of the following payload data packets.
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | F |VDT|# pkts.|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 2: Payload Header
-
- Ident: 24 bits
-
- This 24 bit field is used to associate the Vorbis data to a decoding
- Configuration.
-
- Fragment type (F): 2 bits
-
- This field is set accordingly the following list
-
- 0 = Not Fragmented
- 1 = Start Fragment
- 2 = Continuation Fragment
- 3 = End Fragment
-
- Vorbis Data Type (VDT): 2 bits
-
-
-
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-
-
- This field sets the packet payload type for the Vorbis data. There
- are currently three type of Vorbis payloads.
-
- 0 = Raw Vorbis payload
- 1 = Vorbis Packed Configuration payload
- 2 = Legacy Vorbis Comment payload
- 3 = Reserved
-
- The last 4 bits are the number of complete packets in this payload.
- This provides for a maximum number of 15 Vorbis packets in the
- payload. If the packet contains fragmented data the number of
- packets MUST be set to 0.
-
-2.3. Payload Data
-
- Raw Vorbis packets are unbounded in length currently, although at
- some future point there will likely be a practical limit placed on
- them. Typical Vorbis packet sizes are from very small (2-3 bytes) to
- quite large (8-12 kilobytes). The reference implementation [11]
- typically produces packets less than ~800 bytes, except for the setup
- header packets which are ~4-12 kilobytes. Within an RTP context the
- maximum packet size, including the RTP and payload headers, SHOULD be
- kept below the path MTU to avoid packet fragmentation.
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis packet data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 3: Payload Data Header
-
- Each Vorbis payload packet starts with a two octet length header,
- which is used to represent the size of the following data payload,
- followed by the raw Vorbis data padded to the nearest byte boundary.
-
- For payloads which consist of multiple Vorbis packets the payload
- data consists of the packet length followed by the packet data for
- each of the Vorbis packets in the payload.
-
- The Vorbis packet length header is the length of the Vorbis data
- block only and does not count the length field.
-
- The payload packing of the Vorbis data packets MUST follow the
- guidelines set-out in [4] where the oldest packet occurs immediately
- after the RTP packet header.
-
- Channel mapping of the audio is in accordance with the Vorbis I
-
-
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-
-
- Specification [12].
-
-2.4. Example RTP Packet
-
- Here is an example RTP packet containing two Vorbis packets.
-
- RTP Packet Header:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 2 |0|0| 0 |0| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp (in sample rate units) |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronisation source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 4: Example Packet (RTP Headers)
-
- Payload Data:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 0 | 2 pks |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | next vorbis packet data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 5: Example Packet (Payload Data)
-
- The payload data section of the RTP packet starts with the 24 bit
- Ident field followed by the one octet bitfield header, which has the
- number of Vorbis frames set to 2. Each of the Vorbis data frames is
- prefixed by the two octet length field. The Packet Type and Fragment
- Type are set to 0. The decode Configuration that will be used to
- decode the packets is the one indexed by the ident value.
-
-
-
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-
-
-3. Configuration Headers
-
- Unlike other mainstream audio codecs Vorbis has no statically
- configured probability model. Instead, it packs all entropy decoding
- configuration, VQ and Huffman models into a data block that must be
- transmitted to the decoder along with the compressed data. A decoder
- also requires identification information detailing the number of
- audio channels, bitrates and other information to configure itself
- for a particular compressed data stream. These two blocks of
- information are often referred to collectively as the "codebooks" for
- a Vorbis stream, and are nominally included as special "header"
- packets at the start of the compressed data.
-
- Thus these two codebook header packets must be received by the
- decoder before any audio data can be interpreted. In addition, the
- Vorbis I specification [12] requires the presense of a comment header
- packet which gives simple metadata about the stream. This
- requirement poses problems in RTP, which is often used over
- unreliable transports.
-
- Since this information must be transmitted reliably and, as the RTP
- stream may change certain configuration data mid-session, there are
- different methods for delivering this configuration data to a client,
- both in-band and out-of-band which is detailed below. SDP delivery
- is used to setup an initial state for the client application. The
- changes may be due to different codebooks as well as different
- bitrates of the stream.
-
- The delivery vectors in use are specified by an SDP attribute to
- indicate the method and the optional URI where the Vorbis Packed
- Configuration (Section 3.1.1) Packets could be fetched. Different
- delivery methods MAY be advertised for the same session. The in-band
- Configuration delivery SHOULD be considered as baseline, out-of-band
- delivery methods that don't use RTP will not be described in this
- document. For non chained streams, the Configuration delivery method
- RECOMMENDED is inline the Packed Configuration (Section 3.1.1) in the
- SDP as explained in the IANA considerations (Section 6.1) section.
-
- The 24 bit Ident field is used to map which Configuration will be
- used to decodea packet. When the Ident field changes, it indicates
- that a change in the stream has taken place. The client application
- MUST have in advance the correct configuration and if the client
- detects a change in the Ident value and does not have this
- information it MUST NOT decode the raw Vorbis data associated until
- it fetches the correct Configuration.
-
-
-
-
-
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-
-
-3.1. In-band Header Transmission
-
- The Packed Configuration (Section 3.1.1) Payload is sent in-band with
- the packet type bits set to match the payload type. Clients MUST be
- capable of dealing with fragmentation and periodic re-transmission of
- the configuration headers.
-
-3.1.1. Packed Configuration
-
- A Vorbis Packed Configuration is indicated with the payload type
- field set to 1. Of the three headers, defined in the Vorbis I
- specification [12], the identification and the setup will be packed
- together, the comment header is completely suppressed. Is up to the
- client provide a minimal size comment header to the decoder if
- required by the implementation.
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | xxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 1 | 1|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. | Setup ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 6: Packed Configuration Figure
-
-
-
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-
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-
-
- The Ident field is set with the value that will be used by the Raw
- Payload Packets to address this Configuration. The Fragment type is
- set to 0 since the packet bears the full Packed configuration, the
- number of packet is set to 1.
-
-3.2. Out of Band Transmission
-
- This section, as stated before, won't cover all the possible out-of-
- band delivery methods since they rely to different protocols and be
- linked to a specific application. The following packet definition
- SHOULD be used in out-of-band delivery and MUST be used when
- Configuration is inlined in the SDP.
-
-3.2.1. Packed Headers
-
- As mentioned above the RECOMMENDED delivery vector for Vorbis
- configuration data is via a retrieval method that can be performed
- using a reliable transport protocol. As the RTP headers are not
- required for this method of delivery the structure of the
- configuration data is slightly different. The packed header starts
- with a 32 bit count field which details the number of packed headers
- that are contained in the bundle. Next is the Packed header payload
- for each chained Vorbis stream.
-
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Number of packed headers |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Packed header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Packed header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 7: Packed Headers Overview
-
- Since the Configuration Ident and the Identification Header are fixed
- length there is only a 2 byte length tag to define the length of the
- packed headers.
-
-
-
-
-
-
-
-
-
-
-
-
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-
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-
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. length | Identification Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Setup Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 8: Packed Headers Detail
-
- The key difference between the in-band format and this one, is there
- is no need for the payload header octet.
-
-3.2.1.1. Packed Headers IANA Considerations
-
- The following IANA considerations MUST only be applied to the packed
- headers.
-
- MIME media type name: audio
-
- MIME subtype: vorbis-config
-
- Required Parameters:
-
- None.
-
- Optional Parameters:
-
- None.
-
- Encoding considerations:
-
- This type is only defined for transfer via non RTP protocols as
- specified in RFC XXXX.
-
- Security Considerations:
-
- See Section 6 of RFC 3047.
-
- Interoperability considerations: none
-
- Published specification:
-
-
-
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-
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-
-
- See RFC XXXX for details.
-
- Applications which use this media type:
-
- Vorbis encoded audio, configuration data.
-
- Additional information: none
-
- Person & email address to contact for further information:
-
- Luca Barbato: <lu_zero at gentoo.org>
-
- Intended usage: COMMON
-
- Author/Change controller:
-
- Author: Luca Barbato
-
- Change controller: IETF AVT Working Group
-
-3.3. Loss of Configuration Headers
-
- Unlike the loss of raw Vorbis payload data, loss of a configuration
- header can lead to a situation where it will not be possible to
- successfully decode the stream.
-
- Loss of Configuration Packet results in the halting of stream
- decoding and SHOULD be reported to the client as well as a loss
- report sent via RTCP.
-
-
-4. Comment Headers
-
- With the payload type flag set to 2, this indicates that the packet
- contain the comment metadata, such as artist name, track title and so
- on. These metadata messages are not intended to be fully descriptive
- but to offer basic track/song information. Clients MAY ignore it
- completely. The details on the format of the comments can be found
- in the Vorbis documentation [12].
-
-
-
-
-
-
-
-
-
-
-
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-
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | xxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 2 | 1|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 9: Comment Packet
-
- The 2 bytes length field is necessary since this packet could be
- fragmented.
-
-
-5. Frame Packetizing
-
- Each RTP packet contains either one Vorbis packet fragment, or an
- integer number of complete Vorbis packets (up to a max of 15 packets,
- since the number of packets is defined by a 4 bit value).
-
- Any Vorbis data packet that is less than path MTU SHOULD be bundled
- in the RTP packet with as many Vorbis packets as will fit, up to a
- maximum of 15. Path MTU is detailed in [6] and [7].
-
- If a Vorbis packet, not only data but also Configuration and Comment,
- is larger than 65535 octets it MUST be fragmented. A fragmented
- packet has a zero in the last four bits of the payload header. The
- first fragment will set the Fragment type to 1. Each fragment after
- the first will set the Fragment type to 2 in the payload header. The
- RTP packet containing the last fragment of the Vorbis packet will
- have the Fragment type set to 3. To maintain the correct sequence
- for fragmented packet reception the timestamp field of fragmented
- packets MUST be the same as the first packet sent, with the sequence
- number incremented as normal for the subsequent RTP packets. The
-
-
-
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-
-
- length field shows the fragment length.
-
-5.1. Example Fragmented Vorbis Packet
-
- Here is an example fragmented Vorbis packet split over three RTP
- packets. Each packet contains the standard RTP headers as well as
- the 4 octet Vorbis headers.
-
- Packet 1:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1000 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 1 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 10: Example Fragmented Packet (Packet 1)
-
- In this packet the initial sequence number is 1000 and the timestamp
- is xxxxx. The Fragment type is set to 1, the number of packets field
- is set to 0, and as the payload is raw Vorbis data the VDT field is
- set to 0.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
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-
-
- Packet 2:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1001 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 2 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 11: Example Fragmented Packet (Packet 2)
-
- The Fragment type field is set to 2 and the number of packets field
- is set to 0. For large Vorbis fragments there can be several of
- these type of payload packets. The maximum packet size SHOULD be no
- greater than the path MTU, including all RTP and payload headers.
- The sequence number has been incremented by one but the timestamp
- field remains the same as the initial packet.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-
- Packet 3:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1002 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 3 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 12: Example Fragmented Packet (Packet 3)
-
- This is the last Vorbis fragment packet. The Fragment type is set to
- 3 and the packet count remains set to 0. As in the previous packets
- the timestamp remains set to the first packet in the sequence and the
- sequence number has been incremented.
-
-5.2. Packet Loss
-
- As there is no error correction within the Vorbis stream, packet loss
- will result in a loss of signal. Packet loss is more of an issue for
- fragmented Vorbis packets as the client will have to cope with the
- handling of the Fragment Type. In case of loss of fragments the
- client MUST discard all the remaining fragments and decode the
- incomplete packet. If we use the fragmented Vorbis packet example
- above and the first packet is lost the client MUST detect that the
- next packet has the packet count field set to 0 and the Fragment type
- 2 and MUST drop it. The next packet, which is the final fragmented
- packet, MUST be dropped in the same manner. If the missing packet is
- the last, the received two fragments will be kept and the incomplete
- vorbis packet decoded. Feedback reports on lost and dropped packets
- MUST be sent back via RTCP.
-
- If a particular multicast session has a large number of participants
- care must be taken to prevent an RTCP feedback implosion, [10], in
- the event of packet loss from a large number of participants.
-
-
-
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-
-
- Loss of any of the Configuration fragment will result in the loss of
- the full Configuration packet with the result detailed in the Loss of
- Configuration Headers (Section 3.3) section.
-
-
-6. IANA Considerations
-
- MIME media type name: audio
-
- MIME subtype: vorbis
-
- Required Parameters:
-
- delivery-method: indicates the delivery methods in use, the possible
- values are:inline, in_band, out_band
-
- configuration: the base16 [9] (hexadecimal) representation of the
- Packed Headers (Section 3.2.1).
-
- Optional Parameters:
-
- configuration-uri: the URI of the configuration headers in case of
- out of band transmission. In the form of
- "protocol://path/to/resource/". Depending on the specific method the
- single ident packet could be retrived by their number, or aggregated
- in a single stream.
-
- Encoding considerations:
-
- This type is only defined for transfer via RTP as specified in RFC
- XXXX.
-
- Security Considerations:
-
- See Section 6 of RFC 3047.
-
- Interoperability considerations: none
-
- Published specification:
-
- See the Vorbis documentation [12] for details.
-
- Applications which use this media type:
-
- Audio streaming and conferencing tools
-
- Additional information: none
-
-
-
-
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-
-
- Person & email address to contact for further information:
-
- Luca Barbato: <lu_zero at gentoo.org>
-
- Intended usage: COMMON
-
- Author/Change controller:
-
- Author: Luca Barbato
-
- Change controller: IETF AVT Working Group
-
-6.1. Mapping MIME Parameters into SDP
-
- The information carried in the MIME media type specification has a
- specific mapping to fields in the Session Description Protocol (SDP)
- [5], which is commonly used to describe RTP sessions. When SDP is
- used to specify sessions the mapping are as follows:
-
- o The MIME type ("audio") goes in SDP "m=" as the media name.
-
- o The MIME subtype ("vorbis") goes in SDP "a=rtpmap" as the encoding
- name.
-
- o The parameter "rate" also goes in "a=rtpmap" as clock rate.
-
- o The parameter "channels" also goes in "a=rtpmap" as channel count.
-
- o The mandated parameters "delivery-method" and "configuration" MUST
- be included in the SDP "a=fmpt" attribute.
-
- o The optional parameter "configuration-uri", when present, MUST be
- included in the SDP "a=fmpt" attribute.
-
- If the stream comprises chained Vorbis files and all of them are
- known in advance, the Configuration Packet for each file SHOULD be
- passed to the client using the configuration attribute.
-
- The URI specified in the configuration-uri attribute MUST point to a
- location where all of the Configuration Packets needed for the life
- of the session reside.
-
- The port value is specified by the server application bound to the
- address specified in the c attribute. The bitrate value and channels
- specified in the rtpmap attribute MUST match the Vorbis sample rate
- value. An example is found below.
-
- The answer to any offer, [8], MUST NOT change the URI specified in
-
-
-
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-
-
- the configuration-uri attribute. The Configuration inlined in the
- configuration parameter MAY change.
-
- c=IN IP4/6
- m=audio RTP/AVP 98
- a=rtpmap:98 VORBIS/44100/2
- a=delivery:out_band/http
- a=fmtp:98 delivery-method:in_band,out_band/http;
- configuration=base16string1;
- configuration-uri=http://path/to/the/resource
-
- Note that the payload format (encoding) names are commonly shown in
- upper case. MIME subtypes are commonly shown in lower case. These
- names are case-insensitive in both places. Similarly, parameter
- names are case-insensitive both in MIME types and in the default
- mapping to the SDP a=fmtp attribute. The exception regarding case
- sensitivity is the configuration-uri URI which MUST be regarded as
- being case sensitive.
-
-
-7. Congestion Control
-
- Vorbis clients SHOULD send regular receiver reports detailing
- congestion. A mechanism for dynamically downgrading the stream,
- known as bitrate peeling, will allow for a graceful backing off of
- the stream bitrate. This feature is not available at present so an
- alternative would be to redirect the client to a lower bitrate stream
- if one is available.
-
- If a particular multicast session has a large number of participants
- care must be taken to prevent an RTCP feedback implosion, [10], in
- the event of congestion.
-
-
-8. Examples
-
- The following examples are common usage patterns that MAY be applied
- in such situations, the main scope of this section is to explain
- better usage of the transmission vectors.
-
-8.1. Stream Radio
-
- That is one of the most common situation: one single server streaming
- content in multicast, the clients may start a session at random time.
- The content itself could be a mix of live stream as the dj's speech
- and stored streams as the music she plays.
-
- In this situation we don't know in advance how many codebooks we will
-
-
-
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-
-
- use and. The clients can join anytime and users expect to start
- listening to the content in a short time
-
- On join the client will receive the current Configuration necessary
- to decode the current stream inlined in the SDP. And can start
- decoding the current stream.
-
- When the streamed content changes the new Configuration is sent in-
- band befoe the actual stream, and the Configuration that has to be
- sent inline in the SDP updated.
-
- A serverside optimization would be keep an hash list of the
- Configurations per session to avoid packing them and send the same
- Configuration with different Ident tags
-
- A clientside optimization would be keep a tag list of the
- Configurations per session and don't process configuration packets
- already known.
-
- Let's assume that the client playout buffer can store at least 7
- packets and that is the maximum latency.
-
-
-9. Security Considerations
-
- RTP packets using this payload format are subject to the security
- considerations discussed in the RTP specification [3]. This implies
- that the confidentiality of the media stream is achieved by using
- encryption. Because the data compression used with this payload
- format is applied end-to-end, encryption may be performed on the
- compressed data. Where the size of a data block is set care MUST be
- taken to prevent buffer overflows in the client applications.
-
-
-10. Acknowledgments
-
- This document is a continuation of draft-moffitt-vorbis-rtp-00.txt
- and draft-kerr-avt-vorbis-rtp-04.txt. The MIME type section is a
- continuation of draft-short-avt-rtp-vorbis-mime-00.txt.
-
- Thanks to the AVT, Ogg Vorbis Communities / Xiph.org including Steve
- Casner, Aaron Colwell, Ross Finlayson, Fluendo, Ramon Garcia, Pascal
- Hennequin, Ralph Giles, Tor-Einar Jarnbjo, Colin Law, John Lazzaro,
- Jack Moffitt, Christopher Montgomery, Colin Perkins, Barry Short,
- Mike Smith, Phil Kerr, Michael Sparks, Magnus Westerlund, David
- Barrett, Silvia Pfeiffer, Politecnico di Torino (LS)^3/IMG Group in
- particular Federico Ridolfo, Francesco Varano, Giampaolo Mancini,
- Juan Carlos De Martin.
-
-
-
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-
-
-11. References
-
-11.1. Normative References
-
- [1] Pfeiffer, S., "The Ogg Encapsulation Format Version 0",
- RFC 3533.
-
- [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
- Levels", RFC 2119.
-
- [3] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
- "RTP: A Transport Protocol for real-time applications",
- RFC 3550.
-
- [4] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
- Conferences with Minimal Control.", RFC 3551.
-
- [5] Handley, M. and V. Jacobson, "SDP: Session Description
- Protocol", RFC 2327.
-
- [6] Mogul et al., J., "Path MTU Discovery", RFC 1063.
-
- [7] McCann et al., J., "Path MTU Discovery for IP version 6",
- RFC 1981.
-
- [8] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
- Session Description Protocol (SDP)", RFC 3264.
-
- [9] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings",
- RFC 3548.
-
- [10] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
- "Extended RTP Profile for RTCP-based Feedback (RTP/AVPF)",
- Internet Draft (draft-ietf-avt-rtcp-feedback-11: Work in
- progress).
-
-11.2. Informative References
-
- [11] "libvorbis: Available from the Xiph website,
- http://www.xiph.org".
-
- [12] "Ogg Vorbis I specification: Codec setup and packet decode.
- Available from the Xiph website, http://www.xiph.org".
-
- [13] "Ogg Vorbis I specification: Comment field and header
- specification. Available from the Xiph website,
- http://www.xiph.org".
-
-
-
-
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-
-
-Author's Address
-
- Luca Barbato
- Xiph.Org
-
- Email: lu_zero at gentoo.org
- URI: http://www.xiph.org/
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-Barbato Expires April 24, 2006 [Page 22]
-
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-
-
-Intellectual Property Statement
-
- The IETF takes no position regarding the validity or scope of any
- Intellectual Property Rights or other rights that might be claimed to
- pertain to the implementation or use of the technology described in
- this document or the extent to which any license under such rights
- might or might not be available; nor does it represent that it has
- made any independent effort to identify any such rights. Information
- on the procedures with respect to rights in RFC documents can be
- found in BCP 78 and BCP 79.
-
- Copies of IPR disclosures made to the IETF Secretariat and any
- assurances of licenses to be made available, or the result of an
- attempt made to obtain a general license or permission for the use of
- such proprietary rights by implementers or users of this
- specification can be obtained from the IETF on-line IPR repository at
- http://www.ietf.org/ipr.
-
- The IETF invites any interested party to bring to its attention any
- copyrights, patents or patent applications, or other proprietary
- rights that may cover technology that may be required to implement
- this standard. Please address the information to the IETF at
- ietf-ipr at ietf.org.
-
-
-Disclaimer of Validity
-
- This document and the information contained herein are provided on an
- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-
-Copyright Statement
-
- Copyright (C) The Internet Society (2005). This document is subject
- to the rights, licenses and restrictions contained in BCP 78, and
- except as set forth therein, the authors retain all their rights.
-
-
-Acknowledgment
-
- Funding for the RFC Editor function is currently provided by the
- Internet Society.
-
-
-
-
-Barbato Expires April 24, 2006 [Page 23]
-
-
Deleted: trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-05.xml
===================================================================
--- trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-05.xml 2006-03-20 20:15:52 UTC (rev 11040)
+++ trunk/vorbis/doc/draft-kerr-avt-vorbis-rtp-05.xml 2006-03-20 20:20:37 UTC (rev 11041)
@@ -1,1031 +0,0 @@
-<?xml version='1.0'?>
-<!DOCTYPE rfc SYSTEM 'rfc2629.dtd'>
-<?rfc toc="yes" ?>
-<?rfc compact='yes'?>
-
-<rfc ipr="full3978" docName="RTP Payload Format for Vorbis Encoded Audio">
-
-<front>
-<title>draft-kerr-avt-vorbis-rtp-05</title>
-
-<author initials="L" surname="Barbato" fullname="Luca Barbato">
-<organization>Xiph.Org</organization>
-<address>
-<email>lu_zero at gentoo.org</email>
-<uri>http://www.xiph.org/</uri>
-</address>
-</author>
-
-<date day="21" month="October" year="2005" />
-
-<area>General</area>
-<workgroup>AVT Working Group</workgroup>
-<keyword>I-D</keyword>
-
-<keyword>Internet-Draft</keyword>
-<keyword>Vorbis</keyword>
-<keyword>RTP</keyword>
-
-<abstract>
-<t>
-This document describes an RTP payload format for transporting Vorbis encoded audio. It details the RTP encapsulation mechanism for raw Vorbis data and details the delivery mechanisms for the decoder probability model, referred to as a codebook and other setup information.
-</t>
-
-<t>
-Also included within the document are the necessary details for the use of Vorbis with MIME and Session Description Protocol (SDP).
-</t>
-
-</abstract>
-
-<note title="Editors Note">
-<t>
-All references to RFC XXXX are to be replaced by references to the RFC number of this memo, when published.
-</t>
-</note>
-
-</front>
-
-<middle>
-
-<section anchor="Introduction" title="Introduction">
-
-<t>
-Vorbis is a general purpose perceptual audio codec intended to allow
-maximum encoder flexibility, thus allowing it to scale competitively
-over an exceptionally wide range of bitrates. At the high
-quality/bitrate end of the scale (CD or DAT rate stereo, 16/24 bits), it
-is in the same league as MPEG-2 and MPC.
-Similarly, the version 1.1 reference encoder can encode high-quality CD
-and DAT rate stereo at below 48k bits/sec without resampling to a lower
-rate. Vorbis is also intended for lower and higher sample rates (from
-8kHz telephony to 192kHz digital masters) and a range of channel
-representations (monaural, polyphonic, stereo, quadraphonic, 5.1,
-ambisonic, or up to 255 discrete channels).
-</t>
-
-<t>
-Vorbis encoded audio is generally encapsulated within an Ogg format bitstream <xref target="rfc3533"></xref>, which provides
-framing and synchronization. For the purposes of RTP transport, this layer is unnecessary, and so raw Vorbis packets are used
-in the payload.
-</t>
-
-<section anchor="Terminology" title="Terminology">
-
-<t>
-The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
-in this document are to be interpreted as described in RFC 2119 <xref target="rfc2119"></xref>.
-</t>
-
-</section>
-</section>
-
-<section anchor="Payload Format" title="Payload Format">
-
-<t>
-For RTP based transportation of Vorbis encoded audio the standard RTP header is followed by a 4 octet payload header, then the payload data. The payload headers are used to associate the Vorbis data with its associated decoding codebooks as well as indicating if the following packet contains fragmented Vorbis data and/or the the number of whole Vorbis data frames. The payload data contains the raw Vorbis bitstream information.
-</t>
-
-<section anchor="RTP Header" title="RTP Header">
-
-<t>
-The format of the RTP header is specified in <xref target="rfc3550"></xref> and shown in Figure <xref target="RTP Header Figure"/>. This payload format uses the fields of the header in a manner consistent with that specification.
-</t>
-
-<t>
-<figure anchor="RTP Header Figure" title="RTP Header">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-</t>
-
-<t>
-The RTP header begins with an octet of fields (V, P, X, and CC) to support specialized RTP uses (see <xref target="rfc3550">
-</xref> and <xref target="rfc3551"></xref> for details). For Vorbis RTP, the following values are used.
-</t>
-
-<t>
-Version (V): 2 bits</t>
-<t>
-This field identifies the version of RTP. The version used by this specification is two (2).
-</t>
-
-<t>
-Padding (P): 1 bit</t>
-<t>
-Padding MAY be used with this payload format according to section 5.1 of <xref target="rfc3550"></xref>.
-</t>
-
-<t>
-Extension (X): 1 bit</t>
-<t>
-The Extension bit is used in accordance with <xref target="rfc3550"></xref>.
-</t>
-
-<t>
-CSRC count (CC): 4 bits</t>
-<t>
-The CSRC count is used in accordance with <xref target="rfc3550"></xref>.
-</t>
-
-<t>
-Marker (M): 1 bit</t>
-<t>
-Set to zero. Audio silence suppression not used. This conforms to section 4.1 of <xref target="vorbis-spec-ref"></xref>.
-</t>
-
-<t>
-Payload Type (PT): 7 bits</t>
-<t>
-An RTP profile for a class of applications is expected to assign a payload type for this format, or a dynamically allocated
-payload type SHOULD be chosen which designates the payload as Vorbis.
-</t>
-
-<t>
-Sequence number: 16 bits</t>
-<t>
-The sequence number increments by one for each RTP data packet sent, and may be used by the receiver to detect packet loss and
-to restore packet sequence. This field is detailed further in <xref target="rfc3550"></xref>.
-</t>
-
-<t>
-Timestamp: 32 bits</t>
-<t>
-A timestamp representing the sampling time of the first sample of the first Vorbis packet in the RTP packet. The clock frequency
-MUST be set to the sample rate of the encoded audio data and is conveyed out-of-band as a SDP attribute.
-</t>
-
-<t>
-SSRC/CSRC identifiers: </t>
-<t>
-These two fields, 32 bits each with one SSRC field and a maximum of 16 CSRC fields, are as defined in <xref target="rfc3550">
-</xref>.
-</t>
-
-</section>
-
-<section anchor="Payload Header" title="Payload Header">
-
-<t>
-After the RTP Header section the following 4 octets are the Payload Header. This header is split into a number of bitfields detailing the format of the following payload data packets.
-</t>
-
-<figure anchor="Payload Header Figure" title="Payload Header">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | F |VDT|# pkts.|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-Ident: 24 bits</t>
-<t>
-This 24 bit field is used to associate the Vorbis data to a decoding Configuration.
-</t>
-
-<t>
-Fragment type (F): 2 bits</t>
-<t>
-This field is set accordingly the following list
-</t>
-<vspace blankLines="1" />
-<list style="empty">
-<t> 0 = Not Fragmented</t>
-<t> 1 = Start Fragment</t>
-<t> 2 = Continuation Fragment</t>
-<t> 3 = End Fragment</t>
-</list>
-
-<t>
-Vorbis Data Type (VDT): 2 bits</t>
-<t>
-This field sets the packet payload type for the Vorbis data. There are currently three type of Vorbis payloads.
-</t>
-
-<vspace blankLines="1" />
-<list style="empty">
-<t> 0 = Raw Vorbis payload</t>
-<t> 1 = Vorbis Packed Configuration payload</t>
-<t> 2 = Legacy Vorbis Comment payload</t>
-<t> 3 = Reserved</t>
-</list>
-
-<t>
-The last 4 bits are the number of complete packets in this payload. This provides for a maximum number of 15 Vorbis packets in the payload. If the packet contains fragmented data the number of packets MUST be set to 0.
-</t>
-
-</section>
-
-<section anchor="Payload Data" title="Payload Data">
-
-<t>
-Raw Vorbis packets are unbounded in length currently, although at some future point there will likely be a practical limit placed on them. Typical Vorbis packet sizes are from very small (2-3 bytes) to quite large (8-12 kilobytes). The reference implementation <xref target="libvorbis"></xref> typically produces packets less than ~800 bytes, except for the setup header packets which are ~4-12 kilobytes. Within an RTP context the maximum packet size, including the RTP and payload headers, SHOULD be kept below the path MTU to avoid packet fragmentation.
-</t>
-
-<figure anchor="Payload Data Figure" title="Payload Data Header">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis packet data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-Each Vorbis payload packet starts with a two octet length header, which is used to represent the size of the following data payload, followed by the raw Vorbis data padded to the nearest byte boundary.
-</t>
-
-<t>
-For payloads which consist of multiple Vorbis packets the payload data consists of the packet length followed by the packet data for each of the Vorbis packets in the payload.
-</t>
-
-<t>
-The Vorbis packet length header is the length of the Vorbis data block only and does not count the length field.
-</t>
-
-<t>
-The payload packing of the Vorbis data packets MUST follow the guidelines set-out in <xref target="rfc3551"></xref> where the oldest packet occurs immediately after the RTP packet header.
-</t>
-
-<t>
-Channel mapping of the audio is in accordance with the <xref target="vorbis-spec-ref">Vorbis I Specification</xref>.
-</t>
-
-</section>
-
-<section anchor="Example RTP Packet" title="Example RTP Packet">
-
-<t>
-Here is an example RTP packet containing two Vorbis packets.
-</t>
-
-<t>
-RTP Packet Header:
-</t>
-
-<figure anchor="Example Header Packet (RTP Headers)" title="Example Packet (RTP Headers)">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 2 |0|0| 0 |0| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp (in sample rate units) |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronisation source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-Payload Data:
-</t>
-
-<figure anchor="Example Packet (Payload Data)" title="Example Packet (Payload Data)">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 0 | 2 pks |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | next vorbis packet data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-The payload data section of the RTP packet starts with the 24 bit Ident field followed by the one octet bitfield header, which has the number of Vorbis frames set to 2. Each of the Vorbis data frames is prefixed by the two octet length field. The Packet Type and Fragment Type are set to 0. The decode Configuration that will be used to decode the packets is the one indexed by the ident value.
-</t>
-
-</section>
-</section>
-
-
-
-<section anchor="Configuration Headers" title="Configuration Headers">
-
-<t>
-Unlike other mainstream audio codecs Vorbis has no statically
-configured probability model. Instead, it packs all entropy decoding
-configuration, VQ and Huffman models into a data block that must be
-transmitted to the decoder along with the compressed data. A decoder
-also requires identification information detailing the number of audio
-channels, bitrates and other information to configure itself for a
-particular compressed data stream. These two blocks of information are
-often referred to collectively as the "codebooks" for a Vorbis stream,
-and are nominally included as special "header" packets at the start
-of the compressed data.
-</t>
-
-<t>
-Thus these two codebook header packets must be received by the decoder
-before any audio data can be interpreted. In addition,
-the <xref target="vorbis-spec-ref">Vorbis I specification</xref>
-requires the presense of a comment header packet which gives simple
-metadata about the stream. This requirement poses problems in RTP,
-which is often used over unreliable transports.
-</t>
-
-<t>
-Since this information must be transmitted reliably and, as the RTP
-stream may change certain configuration data mid-session, there are
-different methods for delivering this configuration data to a
-client, both in-band and out-of-band which is detailed below. SDP
-delivery is used to setup an initial state for the client application.
-The changes may be due to different codebooks as well as different
-bitrates of the stream.
-</t>
-
-<t>
-The delivery vectors in use are specified by an SDP attribute to indicate the method and the optional URI where the Vorbis <xref target="Packed Configuration">Packed Configuration</xref> Packets could be fetched. Different delivery methods MAY be advertised for the same session. The in-band Configuration delivery SHOULD be considered as baseline, out-of-band delivery methods that don't use RTP will not be described in this document. For non chained streams, the Configuration delivery method RECOMMENDED is inline the <xref target="Packed Configuration">Packed Configuration</xref> in the SDP as explained in the <xref target="Mapping MIME Parameters into SDP"> IANA considerations</xref> section.
-</t>
-
-<t>
-The 24 bit Ident field is used to map which Configuration will be used to decodea packet. When the Ident field changes, it indicates that a change in the stream has taken place. The client application MUST have in advance the correct configuration and if the client detects a change in the Ident value and does not have this information it MUST NOT decode the raw Vorbis data associated until it fetches the correct Configuration.
-</t>
-
-<section anchor="In-band Header Transmission" title="In-band Header Transmission">
-
-<t>
-The <xref target="Packed Configuration">Packed Configuration</xref> Payload is sent in-band with the packet type bits set to match the payload type. Clients MUST be capable of dealing with fragmentation and periodic re-transmission of the configuration headers.
-</t>
-
-<section anchor="Packed Configuration" title="Packed Configuration">
-
-<t>
-A Vorbis Packed Configuration is indicated with the payload type field set to 1. Of the three headers, defined in the <xref target="vorbis-spec-ref">Vorbis I specification</xref>, the identification and the setup will be packed together, the comment header is completely suppressed. Is up to the client provide a minimal size comment header to the decoder if required by the implementation.
-</t>
-
-<figure anchor="Packed Configuration Figure" title="Packed Configuration Figure">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | xxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 1 | 1|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. | Setup ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>The Ident field is set with the value that will be used by the Raw Payload Packets to address this Configuration. The Fragment type is set to 0 since the packet bears the full Packed configuration, the number of packet is set to 1.</t>
-</section>
-</section>
-
-<section anchor="Out of Band Transmission" title="Out of Band Transmission">
-
-
-<t>
-This section, as stated before, won't cover all the possible out-of-band delivery methods since they rely to different protocols and be linked to a specific application. The following packet definition SHOULD be used in out-of-band delivery and MUST be used when Configuration is inlined in the SDP.
-</t>
-
-<section anchor="Packed Headers" title="Packed Headers">
-
-<t>
-As mentioned above the RECOMMENDED delivery vector for Vorbis configuration data is via a retrieval method that can be performed using a reliable transport protocol. As the RTP headers are not required for this method of delivery the structure of the configuration data is slightly different. The packed header starts with a 32 bit count field which details the number of packed headers that are contained in the bundle. Next is the Packed header payload for each chained Vorbis stream.
-</t>
-
-<figure anchor="Packed Headers Overview Figure" title="Packed Headers Overview">
-<artwork><![CDATA[
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Number of packed headers |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Packed header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Packed header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-Since the Configuration Ident and the Identification Header are fixed length there is only a 2 byte length tag to define the length of the packed headers.
-</t>
-
-<figure anchor="Packed Headers Detail Figure" title="Packed Headers Detail">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. length | Identification Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Setup Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-<t>
-The key difference between the in-band format and this one, is there is no need for the payload header octet.
-</t>
-
-<section anchor="Packed Headers IANA Considerations" title="Packed Headers IANA Considerations">
-
-<t>
-The following IANA considerations MUST only be applied to the packed headers.
-</t>
-
-<t>
-MIME media type name: audio
-</t>
-<t>
-MIME subtype: vorbis-config
-</t>
-
-<t>
-Required Parameters:</t><t>
-None.
-</t>
-
-<t>
-Optional Parameters: </t><t>
-None.
-</t>
-
-<t>
-Encoding considerations:</t><t>
-This type is only defined for transfer via non RTP protocols as specified in RFC XXXX.
-</t>
-
-<t>
-Security Considerations:</t><t>
-See Section 6 of RFC 3047.
-</t>
-
-<t>
-Interoperability considerations: none
-</t>
-
-<t>
-Published specification:</t>
-<t>See RFC XXXX for details.</t>
-
-<t>
-Applications which use this media type:</t><t>
-Vorbis encoded audio, configuration data.
-</t>
-
-<t>
-Additional information: none
-</t>
-
-<t>
-Person & email address to contact for further information:</t><t>
-Luca Barbato: <lu_zero at gentoo.org>
-</t>
-
-<t>
-Intended usage: COMMON
-</t>
-
-<t>Author/Change controller:</t>
-<t>Author: Luca Barbato</t>
-<t>Change controller: IETF AVT Working Group</t>
-
-
-</section>
-</section>
-</section>
-
-<section anchor="Loss of Configuration Headers" title="Loss of Configuration Headers">
-
-<t>
-Unlike the loss of raw Vorbis payload data, loss of a configuration header can lead to a situation where it will not be possible to successfully decode the stream.
-</t>
-
-<t>
-Loss of Configuration Packet results in the halting of stream decoding and SHOULD be reported to the client as well as a loss report sent via RTCP.
-</t>
-
-</section>
-
-<!-- <section anchor="Mapping between Configuration and Stream" title="Mapping between Configuration and Stream">
-
-<t>
-The mapping between the stream and the the configuration is explicit.
-</t>
-
-</section> -->
-
-
-</section>
-
-<section anchor="Comment Headers" title="Comment Headers">
-
-<t>
-With the payload type flag set to 2, this indicates that the packet contain the comment metadata, such as artist name, track title and so on. These metadata messages are not intended to be fully descriptive but to offer basic track/song information. Clients MAY ignore it completely. The details on the format of the comments can be found in the <xref target="vorbis-spec-ref">Vorbis documentation</xref>.
-</t>
-<figure anchor="Comment Packet Figure" title="Comment Packet">
-<artwork><![CDATA[
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | xxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 2 | 1|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>The 2 bytes length field is necessary since this packet could be fragmented.</t>
-
-</section>
-<section anchor="Frame Packetizing" title="Frame Packetizing">
-
-<t>
-Each RTP packet contains either one Vorbis packet fragment, or an integer number of complete Vorbis packets (up to a max of 15 packets, since the number of packets is defined by a 4 bit value).
-</t>
-
-<t>
-Any Vorbis data packet that is less than path MTU SHOULD be bundled in the RTP packet with as many Vorbis packets as will fit, up to a maximum of 15. Path MTU is detailed in <xref target="rfc1063"></xref> and <xref target="rfc1981"></xref>.
-</t>
-
-<t>
-If a Vorbis packet, not only data but also Configuration and Comment, is larger than 65535 octets it MUST be fragmented. A fragmented packet has a zero in the last four bits of the payload header. The first fragment will set the Fragment type to 1. Each fragment after the first will set the Fragment type to 2 in the payload header. The RTP packet containing the last fragment of the Vorbis packet will have the Fragment type set to 3. To maintain the correct sequence for fragmented packet reception the timestamp field of fragmented packets MUST be the same as the first packet sent, with the sequence number incremented as normal for the subsequent RTP packets. The length field shows the fragment length.
-</t>
-
-<section anchor="Example Fragmented Vorbis Packet" title="Example Fragmented Vorbis Packet">
-
-<t>
-Here is an example fragmented Vorbis packet split over three RTP packets. Each packet contains the standard RTP headers as well as the 4 octet Vorbis headers.
-</t>
-
-<figure anchor="Example Fragmented Packet (Packet 1)" title="Example Fragmented Packet (Packet 1)">
-<artwork><![CDATA[
- Packet 1:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1000 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 1 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-In this packet the initial sequence number is 1000 and the timestamp is xxxxx. The Fragment type is set to 1, the number of packets field is set to 0, and as the payload is raw Vorbis data the VDT field is set to 0.
-</t>
-
-<figure anchor="Example Fragmented Packet (Packet 2)" title="Example Fragmented Packet (Packet 2)">
-<artwork><![CDATA[
- Packet 2:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1001 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 2 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-The Fragment type field is set to 2 and the number of packets field is set to 0. For large Vorbis fragments there can be several of these type of payload packets. The maximum packet size SHOULD be no greater than the path MTU, including all RTP and payload headers. The sequence number has been incremented by one but the timestamp field remains the same as the initial packet.
-</t>
-
-<figure anchor="Example Fragmented Packet (Packet 3)" title="Example Fragmented Packet (Packet 3)">
-<artwork><![CDATA[
- Packet 3:
-
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1002 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 3 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-This is the last Vorbis fragment packet. The Fragment type is set to 3 and the packet count remains set to 0. As in the previous packets the timestamp remains set to the first packet in the sequence and the sequence number has been incremented.
-</t>
-</section>
-
-<section anchor="Packet Loss" title="Packet Loss">
-
-<t>
-As there is no error correction within the Vorbis stream, packet loss will result in a loss of signal. Packet loss is more of an issue for fragmented Vorbis packets as the client will have to cope with the handling of the Fragment Type. In case of loss of fragments the client MUST discard all the remaining fragments and decode the incomplete packet. If we use the fragmented Vorbis packet example above and the first packet is lost the client MUST detect that the next packet has the packet count field set to 0 and the Fragment type 2 and MUST drop it. The next packet, which is the final fragmented packet, MUST be dropped in the same manner. If the missing packet is the last, the received two fragments will be kept and the incomplete vorbis packet decoded. Feedback reports on lost and dropped packets MUST be sent back via RTCP.
-</t>
-
-<t>
-If a particular multicast session has a large number of participants care must be taken to prevent an RTCP feedback implosion, <xref target="rtcp-feedback"></xref>, in the event of packet loss from a large number of participants.
-</t>
-
-<t>
-Loss of any of the Configuration fragment will result in the loss of the full Configuration packet with the result detailed in the <xref target="Loss of Configuration Headers">Loss of Configuration Headers</xref> section.
-</t>
-
-</section>
-</section>
-<section anchor="IANA Considerations" title="IANA Considerations">
-
-<t>
-MIME media type name: audio
-</t>
-<t>
-MIME subtype: vorbis
-</t>
-
-<t>
-Required Parameters:
-</t>
-
-<t>
-delivery-method: indicates the delivery methods in use, the possible values are:inline, in_band, out_band
-</t><t>
-configuration: the <xref target="rfc3548">base16</xref> (hexadecimal) representation of the <xref target="Packed Headers">Packed Headers</xref>.
-</t>
-
-<t>
-Optional Parameters: </t><t>
-configuration-uri: the URI of the configuration headers in case of out of band transmission. In the form of "protocol://path/to/resource/". Depending on the specific method the single ident packet could be retrived by their number, or aggregated in a single stream.
-</t>
-
-<t>
-Encoding considerations:</t><t>
-This type is only defined for transfer via RTP as specified
-in RFC XXXX.
-</t>
-
-<t>
-Security Considerations:</t><t>
-See Section 6 of RFC 3047.
-</t>
-
-<t>
-Interoperability considerations: none
-</t>
-
-<t>
-Published specification:</t>
-<t>See the Vorbis documentation <xref target="vorbis-spec-ref"></xref> for details.</t>
-
-<t>
-Applications which use this media type:</t><t>
-Audio streaming and conferencing tools
-</t>
-
-<t>
-Additional information: none
-</t>
-
-<t>
-Person & email address to contact for further information:</t><t>
-Luca Barbato: <lu_zero at gentoo.org>
-</t>
-
-<t>
-Intended usage: COMMON
-</t>
-
-<t>Author/Change controller:</t>
-<t>Author: Luca Barbato</t>
-<t>Change controller: IETF AVT Working Group</t>
-
-<section anchor="Mapping MIME Parameters into SDP" title="Mapping MIME Parameters into SDP">
-
-<t>
-The information carried in the MIME media type specification has a specific mapping to fields in the Session Description Protocol (SDP) <xref target="rfc2327"></xref>, which is commonly used to describe RTP sessions. When SDP is used to specify sessions the mapping are as follows:
-</t>
-
-<vspace blankLines="1" />
-<list style="symbols">
-
-<t>The MIME type ("audio") goes in SDP "m=" as the media name.</t>
-<vspace blankLines="1" />
-
-<t>The MIME subtype ("vorbis") goes in SDP "a=rtpmap" as the encoding name.</t>
-<vspace blankLines="1" />
-
-<t>The parameter "rate" also goes in "a=rtpmap" as clock rate.</t>
-<vspace blankLines="1" />
-
-<t>The parameter "channels" also goes in "a=rtpmap" as channel count.</t>
-<vspace blankLines="1" />
-
-<t>The mandated parameters "delivery-method" and "configuration" MUST be included in the SDP "a=fmpt" attribute.</t>
-<vspace blankLines="1" />
-
-<t>The optional parameter "configuration-uri", when present, MUST be included in the SDP "a=fmpt" attribute.</t>
-
-</list>
-
-<t>
-If the stream comprises chained Vorbis files and all of them are known in advance, the Configuration Packet for each file SHOULD be passed to the client using the configuration attribute.
-</t>
-
-<t>
-The URI specified in the configuration-uri attribute MUST point to a location where all of the Configuration Packets needed for the life of the session reside.
-</t>
-
-<t>
-The port value is specified by the server application bound to the address specified in the c attribute. The bitrate value and channels specified in the rtpmap attribute MUST match the Vorbis sample rate value. An example is found below.
-</t>
-
-<t>
-The answer to any offer, <xref target="rfc3264"></xref>, MUST NOT change the URI specified in the configuration-uri attribute. The Configuration inlined in the configuration parameter MAY change.
-</t>
-
-<vspace blankLines="1" />
-<list style="empty">
-<t>c=IN IP4/6 </t>
-<t>m=audio RTP/AVP 98</t>
-<t>a=rtpmap:98 VORBIS/44100/2</t>
-<t>a=delivery:out_band/http</t>
-<t>a=fmtp:98 delivery-method:in_band,out_band/http; configuration=base16string1; configuration-uri=http://path/to/the/resource</t>
-</list>
-
-<t>
-Note that the payload format (encoding) names are commonly shown in upper case. MIME subtypes are commonly shown in lower case. These names are case-insensitive in both places. Similarly, parameter names are case-insensitive both in MIME types and in the default mapping to the SDP a=fmtp attribute. The exception regarding case sensitivity is the configuration-uri URI which MUST be regarded as being case sensitive.
-</t>
-
-</section>
-</section>
-
-
-<section anchor="Congestion Control" title="Congestion Control">
-
-<t>
-Vorbis clients SHOULD send regular receiver reports detailing congestion. A mechanism for dynamically downgrading the stream, known as bitrate peeling, will allow for a graceful backing off of the stream bitrate. This feature is not available at present so an alternative would be to redirect the client to a lower bitrate stream if one is available.
-</t>
-
-<t>
-If a particular multicast session has a large number of participants care must be taken to prevent an RTCP feedback implosion, <xref target="rtcp-feedback"></xref>, in the event of congestion.
-</t>
-
-</section>
-
-<section anchor="Examples" title="Examples">
-
-<t>
-The following examples are common usage patterns that MAY be applied in such situations, the main scope of this section is to explain better usage of the transmission vectors.
-</t>
-
-<section anchor="Stream Radio" title="Stream Radio">
-
-<t>That is one of the most common situation: one single server streaming content in multicast, the clients may start a session at random time. The content itself could be a mix of live stream as the dj's speech and stored streams as the music she plays.</t>
-
-<t>In this situation we don't know in advance how many codebooks we will use and. The clients can join anytime and users expect to start listening to the content in a short time</t>
-
-<t>On join the client will receive the current Configuration necessary to decode the current stream inlined in the SDP. And can start decoding the current stream.</t>
-
-<t>When the streamed content changes the new Configuration is sent in-band befoe the actual stream, and the Configuration that has to be sent inline in the SDP updated.</t>
-
-<t>A serverside optimization would be keep an hash list of the Configurations per session to avoid packing them and send the same Configuration with different Ident tags</t>
-<t>A clientside optimization would be keep a tag list of the Configurations per session and don't process configuration packets already known.</t>
-
-<t>Let's assume that the client playout buffer can store at least 7 packets and that is the maximum latency.</t>
-
-</section>
-</section>
-
-<section anchor="Security Considerations" title="Security Considerations">
-<t>
-RTP packets using this payload format are subject to the security considerations discussed in the RTP specification
-<xref target="rfc3550"></xref>. This implies that the confidentiality of the media stream is achieved by using
-encryption. Because the data compression used with this payload format is applied end-to-end, encryption may be performed on the
-compressed data. Where the size of a data block is set care MUST be taken to prevent buffer overflows in the client applications.
-</t>
-
-</section>
-
-<section anchor="Acknowledgments" title="Acknowledgments">
-
-<t>
-This document is a continuation of draft-moffitt-vorbis-rtp-00.txt and draft-kerr-avt-vorbis-rtp-04.txt. The MIME type section is a continuation of draft-short-avt-rtp-vorbis-mime-00.txt.
-</t>
-
-<t>
-Thanks to the AVT, Ogg Vorbis Communities / Xiph.org including Steve Casner, Aaron Colwell, Ross Finlayson, Fluendo, Ramon Garcia, Pascal Hennequin, Ralph Giles, Tor-Einar Jarnbjo, Colin Law, John Lazzaro, Jack Moffitt, Christopher Montgomery, Colin Perkins, Barry Short, Mike Smith, Phil Kerr, Michael Sparks, Magnus Westerlund, David Barrett, Silvia Pfeiffer, Politecnico di Torino (LS)³/IMG Group in particular Federico Ridolfo, Francesco Varano, Giampaolo Mancini, Juan Carlos De Martin.
-</t>
-
-</section>
-
-</middle>
-
-<back>
-
-<references title="Normative References">
-
-<reference anchor="rfc3533">
-<front>
-<title>The Ogg Encapsulation Format Version 0</title>
-<author initials="S." surname="Pfeiffer" fullname="Silvia Pfeiffer"></author>
-</front>
-<seriesInfo name="RFC" value="3533" />
-</reference>
-
-<reference anchor="rfc2119">
-<front>
-<title>Key words for use in RFCs to Indicate Requirement Levels </title>
-<author initials="S." surname="Bradner" fullname="Scott Bradner"></author>
-</front>
-<seriesInfo name="RFC" value="2119" />
-</reference>
-
-<reference anchor="rfc3550">
-<front>
-<title>RTP: A Transport Protocol for real-time applications</title>
-<author initials="H." surname="Schulzrinne" fullname=""></author>
-<author initials="S." surname="Casner" fullname=""></author>
-<author initials="R." surname="Frederick" fullname=""></author>
-<author initials="V." surname="Jacobson" fullname=""></author>
-</front>
-<seriesInfo name="RFC" value="3550" />
-</reference>
-
-<reference anchor="rfc3551">
-<front>
-<title>RTP Profile for Audio and Video Conferences with Minimal Control.</title>
-<author initials="H." surname="Schulzrinne" fullname=""></author>
-<author initials="S." surname="Casner" fullname=""></author>
-</front>
-<date month="July" year="2003" />
-<seriesInfo name="RFC" value="3551" />
-</reference>
-
-<reference anchor="rfc2327">
-<front>
-<title>SDP: Session Description Protocol</title>
-<author initials="M." surname="Handley" fullname="Mark Handley"></author>
-<author initials="V." surname="Jacobson" fullname="Van Jacobson"></author>
-</front>
-<seriesInfo name="RFC" value="2327" />
-</reference>
-
-<reference anchor="rfc1063">
-<front>
-<title>Path MTU Discovery</title>
-<author initials="J." surname="Mogul et al." fullname="J. Mogul et al."></author>
-</front>
-<seriesInfo name="RFC" value="1063" />
-</reference>
-
-<reference anchor="rfc1981">
-<front>
-<title>Path MTU Discovery for IP version 6</title>
-<author initials="J." surname="McCann et al." fullname="J. McCann et al."></author>
-</front>
-<seriesInfo name="RFC" value="1981" />
-</reference>
-
-<reference anchor="rfc3264">
-<front>
-<title>An Offer/Answer Model with Session Description Protocol (SDP)</title>
-<author initials="J." surname="Rosenberg" fullname="Jonathan Rosenberg"></author>
-<author initials="H." surname="Schulzrinne" fullname="Henning Schulzrinne"></author>
-</front>
-<seriesInfo name="RFC" value="3264" />
-</reference>
-
-<reference anchor="rfc3548">
-<front>
-<title>The Base16, Base32, and Base64 Data Encodings</title>
-<author initials="S." surname="Josefsson" fullname="Simon Josefsson"></author>
-</front>
-<seriesInfo name="RFC" value="3548" />
-</reference>
-
-<reference anchor="rtcp-feedback">
-<front>
-<title>Extended RTP Profile for RTCP-based Feedback (RTP/AVPF)</title>
-<author initials="J." surname="Ott" fullname="Joerg Ott"></author>
-<author initials="S." surname="Wenger" fullname="Stephan Wenger"></author>
-<author initials="N." surname="Sato" fullname="Noriyuki Sato"></author>
-<author initials="C." surname="Burmeister" fullname="Carsten Burmeister"></author>
-<author initials="J." surname="Rey" fullname="Jose Rey"></author>
-</front>
-<seriesInfo name="Internet Draft" value="(draft-ietf-avt-rtcp-feedback-11: Work in progress)" />
-</reference>
-
-
-</references>
-
-<references title="Informative References">
-<reference anchor="libvorbis">
-<front>
-<title>libvorbis: Available from the Xiph website, http://www.xiph.org</title>
-</front>
-</reference>
-
-<reference anchor="vorbis-spec-ref">
-<front>
-<title>Ogg Vorbis I specification: Codec setup and packet decode. Available from the Xiph website, http://www.xiph.org</title>
-</front>
-</reference>
-
-<reference anchor="v-comment">
-<front>
-<title>Ogg Vorbis I specification: Comment field and header specification. Available from the Xiph website,
-http://www.xiph.org</title>
-</front>
-</reference>
-
-</references>
-</back>
-</rfc>
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