[xiph-commits] r14399 - trunk/vorbis/doc
lu_zero at svn.xiph.org
lu_zero at svn.xiph.org
Mon Jan 14 11:17:32 PST 2008
Author: lu_zero
Date: 2008-01-14 11:17:32 -0800 (Mon, 14 Jan 2008)
New Revision: 14399
Added:
trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-09.txt
trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-09.xml
Removed:
trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-08.txt
trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-08.xml
Log:
Bump version
Deleted: trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-08.txt
===================================================================
--- trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-08.txt 2008-01-14 19:14:25 UTC (rev 14398)
+++ trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-08.txt 2008-01-14 19:17:32 UTC (rev 14399)
@@ -1,1401 +0,0 @@
-
-
-
-AVT Working Group L. Barbato
-Internet-Draft Xiph
-Expires: July 8, 2008 Jan 05, 2008
-
-
- RTP Payload Format for Vorbis Encoded Audio
- draft-ietf-avt-rtp-vorbis-08
-
-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 July 8, 2008.
-
-Copyright Notice
-
- Copyright (C) The IETF Trust (2008).
-
-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 this memo are media type registrations, and the
- details necessary for the use of Vorbis with the Session Description
- Protocol (SDP).
-
-
-
-Barbato Expires July 8, 2008 [Page 1]
-
-Internet-Draft Vorbis RTP Payload Format Jan 2008
-
-
-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. Conformance and Document Conventions . . . . . . . . . . . 3
- 2. Payload Format . . . . . . . . . . . . . . . . . . . . . . . . 3
- 2.1. RTP Header . . . . . . . . . . . . . . . . . . . . . . . . 4
- 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 . . . . . . . . . . . . . . . . . 11
- 3.2.1. Packed Headers . . . . . . . . . . . . . . . . . . . . 11
- 3.3. Loss of Configuration Headers . . . . . . . . . . . . . . 12
- 4. Comment Headers . . . . . . . . . . . . . . . . . . . . . . . 12
- 5. Frame Packetization . . . . . . . . . . . . . . . . . . . . . 13
- 5.1. Example Fragmented Vorbis Packet . . . . . . . . . . . . . 14
- 5.2. Packet Loss . . . . . . . . . . . . . . . . . . . . . . . 16
- 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
- 6.1. Packed Headers IANA Considerations . . . . . . . . . . . . 18
- 7. SDP related considerations . . . . . . . . . . . . . . . . . . 20
- 7.1. Mapping Media Type Parameters into SDP . . . . . . . . . . 20
- 7.1.1. SDP Example . . . . . . . . . . . . . . . . . . . . . 21
- 7.2. Usage with the SDP Offer/Answer Model . . . . . . . . . . 21
- 8. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
- 8.1. Stream Radio . . . . . . . . . . . . . . . . . . . . . . . 22
- 9. Security Considerations . . . . . . . . . . . . . . . . . . . 22
- 10. Copying Conditions . . . . . . . . . . . . . . . . . . . . . . 23
- 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23
- 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
- 12.1. Normative References . . . . . . . . . . . . . . . . . . . 23
- 12.2. Informative References . . . . . . . . . . . . . . . . . . 24
-
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-Barbato Expires July 8, 2008 [Page 2]
-
-Internet-Draft Vorbis RTP Payload Format Jan 2008
-
-
-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-4 AAC. 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 [11], 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. Conformance and Document Conventions
-
- 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 BCP 14, [1] and
- indicate requirement levels for compliant implementations.
- Requirements apply to all implementations unless otherwise stated.
-
- An implementation is a software module that supports one of the media
- types defined in this document. Software modules may support
- multiple media types, but conformance is considered individually for
- each type.
-
- Implementations that fail to satisfy one or more "MUST" requirements
- are considered non-compliant. Implementations that satisfy all
- "MUST" requirements, but fail to satisfy one or more "SHOULD"
- requirements, are said to be "conditionally compliant". All other
- implementations are "unconditionally compliant".
-
-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. There are 3 types of Vorbis data, an RTP
- payload MUST contain just one of them at a time.
-
-
-
-
-
-Barbato Expires July 8, 2008 [Page 3]
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-
-
-2.1. RTP Header
-
- The format of the RTP header is specified in [2] and shown in Figure
- Figure 1. This payload format uses the fields of the header in a
- manner consistent with that specification.
-
-
- 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 [2] and [3] 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 [2].
-
- Extension (X): 1 bit
-
- The Extension bit is used in accordance with [2].
-
- CSRC count (CC): 4 bits
-
- The CSRC count is used in accordance with [2].
-
- Marker (M): 1 bit
-
- Set to zero. Audio silence suppression not used. This conforms to
- section 4.1 of [10].
-
-
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-
- 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 [2].
-
- Timestamp: 32 bits
-
- A timestamp representing the sampling time of the first sample of the
- first Vorbis packet in the RTP payload. The clock frequency MUST be
- set to the sample rate of the encoded audio data and is conveyed out-
- of-band (e.g. as an 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 [2].
-
-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. It is stored as network byte order integer.
-
- Fragment type (F): 2 bits
-
- This field is set according to the following list
-
-
-
-
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-Barbato Expires July 8, 2008 [Page 5]
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-
- 0 = Not Fragmented
- 1 = Start Fragment
- 2 = Continuation Fragment
- 3 = End Fragment
-
- Vorbis Data Type (VDT): 2 bits
-
- This field specifies the kind of Vorbis data stored in this RTP
- packet. There are currently three different types of Vorbis
- payloads. Each packet MUST contain only a single type of Vorbis
- packet (e.g. you must not aggregate configuration and comment packets
- in the same RTP payload)
-
- 0 = Raw Vorbis payload
- 1 = Vorbis Packed Configuration payload
- 2 = Legacy Vorbis Comment payload
- 3 = Reserved
-
- The packets with a VDT 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 payload 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 [12] 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 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 in bytes of the following data
- payload, followed by the raw Vorbis data padded to the nearest byte
-
-
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-Barbato Expires July 8, 2008 [Page 6]
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-
- boundary, as explained by the vorbis specification [10]. The length
- value is stored as network byte order integer.
-
- 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 include the length field.
-
- The payload packing of the Vorbis data packets MUST follow the
- guidelines set-out in [3] where the oldest Vorbis packet occurs
- immediately after the RTP packet header. Subsequent Vorbis packets,
- if any, MUST follow in temporal order.
-
- Channel mapping of the audio is in accordance with the Vorbis I
- Specification [10].
-
-2.4. Example RTP Packet
-
- Here is an example RTP payload containing two Vorbis 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
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 2 |0|0| 0 |0| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp (in sample rate units) |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronisation source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 0 | 2 pks |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | next vorbis packet data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
-
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-
- Figure 4: Example Raw Vorbis Packet
-
- 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.
-
-3. Configuration Headers
-
- Unlike other mainstream audio codecs Vorbis has no statically
- configured probability model. Instead, it packs all entropy decoding
- configuration, Vector Quantization 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 [10] 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 typically 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 RTP stream.
-
- The delivery vectors in use can be 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 recommended Configuration
- delivery method is inline the Packed Configuration (Section 3.1.1) in
- the SDP as explained in the IANA considerations (Section 7.1).
-
- The 24 bit Ident field is used to map which Configuration will be
-
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- 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.
-
-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 Vorbis Data Type. Clients MUST
- be capable of dealing with fragmentation and periodic re-transmission
- of [14] the configuration headers. The RTP timestamp value MUST
- reflect the transmission time of the next data packet.
-
-3.1.1. Packed Configuration
-
- A Vorbis Packed Configuration is indicated with the Vorbis Data Type
- field set to 1. Of the three headers defined in the Vorbis I
- specification [10], the Identification and the Setup MUST be packed
- as they are, while the comment header MAY be replaced with a dummy
- one.
-
- The packed configuration follows a generic way to store Xiph codec
- configurations: The first field stores the number of the following
- packets minus one (count field), the next ones represent the size of
- the headers (length fields), the headers immediately follow the list
- of length fields. The size of the last header is implicit.
-
- The count and the length fields are encoded using the following
- logic: the data is in network byte order, every byte has the most
- significant bit used as flag and the following 7 used to store the
- value. The first N bit are to be taken, where N is number of bits
- needed to represent the value, taken modulo 7, and stored in the
- first byte. If there are more bits, the flag bit is set to 1 and the
- subsequent 7bit are stored in the following byte, if there are
- remaining bits set the flag to 1 and the same procedure is repeated.
- The ending byte has the flag bit set to 0. In order to decode it is
- enough to iterate over the bytes until the flag bit set to 0, for
- every byte the data is added to the accumulated value multiplied by
- 128.
-
- The headers are packed in the same order they are present in ogg:
- Identification, Comment, Setup.
-
- The 2 byte length tag defines the length of the packed headers as the
- sum of the Configuration, Comment and Setup lengths.
-
-
-
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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 | 1 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | n. of headers | length1 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length2 | Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification | Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment | Setup ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 5: 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.
-
-
-
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-
-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
- 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 (network byte ordered) 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 6: Packed Headers Overview
-
-
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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 ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. | n. of headers | length1 | length2 ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. | Identification Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .................................................................
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. | Comment Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .................................................................
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Setup Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .................................................................
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 7: Packed Headers Detail
-
- The key difference between the in-band format and this one, is that
- there is no need for the payload header octet. In this figure the
- comment has a size bigger than 127 bytes.
-
-3.3. Loss of Configuration Headers
-
- Unlike the loss of raw Vorbis payload data, loss of a configuration
- header lead to a situation where it will not be possible to
- successfully decode the stream. Implementations MAY try to recover
- from error by requesting again the missing Configuration or, if the
- delivery method is in-band, by buffering the payloads waiting for the
- Configuration needed to decode them. The baseline reaction SHOULD be
- either reset or end the RTP session.
-
-4. Comment Headers
-
- With the Vorbis Data 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 [10].
-
-
-
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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 8: Comment Packet
-
- The 2 bytes length field is necessary since this packet could be
- fragmented.
-
-5. Frame Packetization
-
- Each RTP payload 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 payload 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 consecutive fragments MUST be sent without any
- other payloads being sent between the first and the last fragment.
- The RTP payload 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
-
-
-
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-
-
- the sequence number incremented as normal for the subsequent RTP
- payloads, this will affect the RTCP jitter measurement. The length
- field shows the fragment length.
-
-5.1. Example Fragmented Vorbis Packet
-
- Here is an example fragmented Vorbis packet split over three RTP
- payloads. Each of them 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 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 12345 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 1 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 9: Example Fragmented Packet (Packet 1)
-
- In this payload the initial sequence number is 1000 and the timestamp
- is 12345. 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 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 12345 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 2 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 10: 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 this
- type of payloads. 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 payload.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
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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 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 12345 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 3 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
- Figure 11: Example Fragmented Packet (Packet 3)
-
- This is the last Vorbis fragment payload. The Fragment type is set
- to 3 and the packet count remains set to 0. As in the previous
- payloads the timestamp remains set to the first payload timestamp 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 Vorbis fragments and decode the
- incomplete packet. If we use the fragmented Vorbis packet example
- above and the first RTP payload is lost the client MUST detect that
- the next RTP payload has the packet count field set to 0 and the
- Fragment type 2 and MUST drop it. The next RTP payload, which is the
- final fragmented packet, MUST be dropped in the same manner. If the
- missing RTP payload is the last, the received two fragments will be
- kept and the incomplete Vorbis packet decoded.
-
- 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.
-
-
-
-
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-
-
-6. IANA Considerations
-
- Type name: audio
-
- Subtype name: vorbis
-
- Required parameters:
-
- rate: indicates the RTP timestamp clock rate as described in RTP
- Profile for Audio and Video Conferences with Minimal Control.
- [3]
-
- channels: indicates the number of audio channels as described in
- RTP Profile for Audio and Video Conferences with Minimal
- Control. [3]
-
- delivery-method: indicates the delivery methods in use, the
- possible values are: inline, in_band, out_band. The parameter
- MAY be included multiple time, followed by the configuration or
- configuration-uri parameter associated.
-
- configuration: the base64 [9] representation of the Packed
- Headers (Section 3.2.1). It MUST follow the associated
- delivery-method parameter ("inline").
-
- Optional parameters:
-
- configuration-uri: the URI [4] of the configuration headers in
- case of out of band transmission. In the form of
- "scheme://path/to/resource/", depending on the specific method,
- a single configuration packet could be retrived by its Ident
- number, or multiple packets could be aggregated in a single
- stream. Non hierarchical protocols MAY point to a resource
- using their specific syntax.
-
- Encoding considerations:
-
- This media type is framed and contains binary data.
-
- Security considerations:
-
- See Section 10 of RFC XXXX.
-
- Interoperability considerations:
-
- None
-
-
-
-
-
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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://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 [2]
-
- Author:
-
- Luca Barbato
-
- Change controller:
-
- IETF AVT Working Group delegated from the IESG
-
-
-6.1. Packed Headers IANA Considerations
-
- The following IANA considerations MUST only be applied to the Packed
- Headers (Section 3.2.1).
-
-
-
-
-
-
-
-
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-
-
- Type name: audio
-
- Subtype name: vorbis-config
-
- Required parameters:
-
- None
-
- Optional parameters:
-
- None
-
- Encoding considerations:
-
- This media type contains binary data.
-
- Security considerations:
-
- See Section 10 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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-
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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 delegated from the IESG
-
-7. SDP related considerations
-
- The following paragraphs define the mapping of the parameters
- described in the IANA considerations section and their usage in the
- Offer/Answer Model [8].
-
-7.1. Mapping Media Type Parameters into SDP
-
- The information carried in the 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 type name ("audio") goes in SDP "m=" as the media name.
-
- o The subtype name ("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=fmtp" attribute.
-
- o The optional parameter "configuration-uri", when present, MUST be
- included in the SDP "a=fmtp" 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.
-
-
-
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-
-
- The port value is specified by the server application bound to the
- address specified in the c= line. The sample rate and channel count
- value specified in the rtpmap attribute SHOULD match the current
- Vorbis stream or considered the maximum number of channels to be
- expected and the least common multiple for the session. The
- Configuration payload delivers the exact information, thus the SDP
- information SHOULD be considered as a hint. An example is found
- below.
-
-7.1.1. 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 URIs provided. The inline
- base64 [9] configuration string is folded in this example due to RFC
- line length limitations.
- c=IN IP4 192.0.2.1
- m=audio RTP/AVP 98
- a=rtpmap:98 vorbis/44100/2
- a=fmtp:98 delivery-method=inline;
- configuration=AAAAAZ2f4g9NAh4aAXZvcmJpcwA...; delivery-
- method=out_band; configuration-uri=rtsp://path/to/the/resource;
- delivery-method=out_band;
- configuration-uri=http://another/path/to/resource/;
-
- Note that the payload format (encoding) names are commonly shown in
- upper case. Media Type subtypes are commonly shown in lower case.
- These names are case-insensitive in both places. Similarly,
- parameter names are case-insensitive both in Media Type 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. The a=fmtp line is a single line
- even if it is shown as multiple lines in this document for clarity.
-
-7.2. Usage with the SDP Offer/Answer Model
-
- The only parameter negotiable is the delivery method. All the others
- are declarative: 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.
-
-8. Example
-
- The following example shows a common usage pattern that MAY be
- applied in such situation, the main scope of this section is to
- explain better usage of the transmission vectors.
-
-
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-
-
-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 webjockey'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
- 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 in-band method is
- unreliable, an out of band fallback is provided.
-
- The client may choose to fetch the Configuration from the alternate
- source as soon as it discovers a Configuration packet got lost in-
- band or use selective retransmission [13], 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 [2], the base64
- specification [9] and the URI Generic syntax specification [4].
- Among other considerations, this implies that the confidentiality of
- the media stream is archieved 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. Additional care
- MAY be needed for delivery methods that point to external resources,
- using secure protocols to fetch the configuration payloads. Where
- the size of a data block is set, care MUST be taken to prevent buffer
- overflows in the client applications.
-
-
-
-
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-
-
-10. Copying Conditions
-
- The authors agree to grant third parties the irrevocable right to
- copy, use and distribute the work, with or without modification, in
- any medium, without royalty, provided that, unless separate
- permission is granted, redistributed modified works do not contain
- misleading author, version, name of work, or endorsement information.
-
-11. Acknowledgments
-
- This document is a continuation of draft-moffitt-vorbis-rtp-00.txt
- and draft-kerr-avt-vorbis-rtp-04.txt. The Media Type declaration is
- a continuation of draft-short-avt-rtp-vorbis-mime-00.txt.
-
- Thanks to the AVT, Vorbis Communities / Xiph.Org Foundation 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, Dario Gallucci, Juan
- Carlos De Martin.
-
-12. References
-
-12.1. Normative References
-
- [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
- Levels", RFC 2119.
-
- [2] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
- "RTP: A Transport Protocol for real-time applications", STD 64,
- RFC 3550.
-
- [3] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
- Conferences with Minimal Control.", STD 65, RFC 3551.
-
- [4] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
- Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986.
-
- [5] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
- Description Protocol", RFC 4566, July 2006.
-
- [6] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
- November 1990.
-
- [7] McCann et al., J., "Path MTU Discovery for IP version 6",
-
-
-
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-
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-
-
- 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] "Ogg Vorbis I specification: Codec setup and packet decode.
- Available from the Xiph website,
- http://xiph.org/vorbis/doc/Vorbis_I_spec.html".
-
-12.2. Informative References
-
- [11] Pfeiffer, S., "The Ogg Encapsulation Format Version 0",
- RFC 3533.
-
- [12] "libvorbis: Available from the dedicated website,
- http://vorbis.com".
-
- [13] Friedman, T., Caceres, R., and A. Clark, "RTP Control Protocol
- Extended Reports (RTCP XR)", RFC 3611, November 2003.
-
- [14] Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R. Hakenberg,
- "RTP Retransmission Payload Format", RFC 4588, July 2006.
-
-Author's Address
-
- Luca Barbato
- Xiph.Org Foundation
-
- EMail: lu_zero at gentoo.org
- URI: http://xiph.org/
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
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-
-
-Full Copyright Statement
-
- Copyright (C) The IETF Trust (2008).
-
- 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.
-
- 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, THE IETF TRUST 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.
-
-Intellectual Property
-
- 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.
-
-Acknowledgement
-
- Funding for the RFC Editor function is provided by the IETF
- Administrative Support Activity (IASA).
-
-
-
-
-
-
-
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Deleted: trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-08.xml
===================================================================
--- trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-08.xml 2008-01-14 19:14:25 UTC (rev 14398)
+++ trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-08.xml 2008-01-14 19:17:32 UTC (rev 14399)
@@ -1,1352 +0,0 @@
-<?xml version="1.0"?>
-<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
-<?rfc toc="yes" ?>
-<?rfc compact="yes" ?>
-<?rfc rfcedstyle="yes" ?>
-
-<rfc ipr="full3978" docName="draft-ietf-avt-rtp-vorbis-08">
-
-<front>
-<title abbrev="Vorbis RTP Payload Format">RTP Payload Format for Vorbis Encoded Audio</title>
-
-<author initials="L" surname="Barbato" fullname="Luca Barbato">
-<organization abbrev="Xiph">Xiph.Org Foundation</organization>
-<address>
-<email>lu_zero at gentoo.org</email>
-<uri>http://xiph.org/</uri>
-</address>
-</author>
-
-<date day="14" month="Jan" year="2008" />
-
-<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 this memo are media type registrations, and the details
-necessary for the use of Vorbis with the 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-4 AAC.
-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="Conformance and Document Conventions">
-
-<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 BCP 14, <xref target="rfc2119"/> and indicate requirement levels for compliant implementations. Requirements apply to all implementations unless otherwise stated.</t>
-<t>An implementation is a software module that supports one of the media types defined in this document. Software modules may support multiple media types, but conformance is considered individually for each type.</t>
-<t>Implementations that fail to satisfy one or more "MUST" requirements are considered non-compliant. Implementations that satisfy all "MUST" requirements, but fail to satisfy one or more "SHOULD" requirements, are said to be "conditionally compliant". All other implementations are "unconditionally compliant".</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. There are 3 types of Vorbis
-data, an RTP payload MUST contain just one of them at a time.
-</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 payload. The clock frequency MUST be set to the sample
-rate of the encoded audio data and is conveyed out-of-band (e.g. as an 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. It is stored as network byte order integer.
-</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 specifies the kind of Vorbis data stored in this RTP packet. There
-are currently three different types of Vorbis payloads. Each packet MUST contain only a single type of Vorbis packet (e.g. you must not aggregate configuration and comment packets in the same RTP payload)
-</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 VDT 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
-payload 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 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 in bytes of the following data payload, followed by the
-raw Vorbis data padded to the nearest byte boundary, as explained by the <xref target="vorbis-spec-ref">vorbis specification</xref>. The length value is stored
-as network byte order integer.
-</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 include 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 Vorbis packet occurs
-immediately after the RTP packet header. Subsequent Vorbis 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 payload containing two Vorbis packets.
-</t>
-
-<figure anchor="Example Raw Vorbis Packet" title="Example Raw Vorbis 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
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 2 |0|0| 0 |0| PT | sequence number |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | timestamp (in sample rate units) |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronisation source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 0 | 0 | 2 pks |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | next vorbis packet data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis 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, Vector Quantization 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 typically 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 RTP stream.
-</t>
-
-<!--
-<t>
-The delivery vectors in use can be 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.
--->
-<t>For non chained streams, the recommended Configuration delivery
-method is inline the <xref target="Packed Configuration">Packed Configuration</xref> in the SDP as explained in the <xref target="Mapping Media Type Parameters into SDP"> IANA considerations</xref>.
-</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 Vorbis Data Type.
-Clients MUST be capable of dealing with fragmentation and periodic
-<xref target="rfc4588">re-transmission of</xref> the configuration headers.
-The RTP timestamp value MUST reflect the transmission time of the first data packet for which this configuration applies.
-</t>
-
-<section anchor="Packed Configuration" title="Packed Configuration">
-
-<t>
-A Vorbis Packed Configuration is indicated with the Vorbis Data 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 MUST be packed as they are, while the comment
-header MAY be replaced with a dummy one.</t>
-<t>
-The packed configuration follows a generic way to store Xiph codec
-configurations: The first field stores the number of the following packets
-minus one (count field), the next ones represent the size of the headers
-(length fields), the headers immediately follow the list of length fields.
-The size of the last header is implicit.</t>
-<t>
-The count and the length fields are encoded using the following logic: the data
-is in network byte order, every byte has the most significant bit used as flag
-and the following 7 used to store the value.
-The first N bit are to be taken, where N is number of bits needed to represent
-the value, taken modulo 7, and stored in the first byte.
-If there are more bits, the flag bit is set to 1 and the subsequent 7bit are
-stored in the following byte, if there are remaining bits set the flag to 1 and
-the same procedure is repeated.
-The ending byte has the flag bit set to 0. In order to decode it is enough to
-iterate over the bytes until the flag bit set to 0, for every byte the data is
-added to the accumulated value multiplied by 128.</t>
-<t>
-The headers are packed in the same order they are present in ogg:
-Identification, Comment, Setup.</t>
-
-<t>
-The 2 byte length tag defines the length of the packed headers as the sum of
-the Configuration, Comment and Setup lengths.</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 | 1 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | n. of headers | length1 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length2 | Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Identification | Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment | 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>
-The following packet definition 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 (network byte ordered) 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>
-
-<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 ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. | n. of headers | length1 | length2 ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. | Identification Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .................................................................
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. | Comment Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .................................................................
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Comment Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Setup Header ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .................................................................
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-<t>
-The key difference between the in-band format and this one, is that there is no
-need for the payload header octet. In this figure the comment has a size bigger
-than 127 bytes.
-</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
-lead to a situation where it will not be possible to successfully decode the
-stream. Implementations MAY try to recover from error by requesting again the
-missing Configuration or, if the delivery method is in-band, by buffering the
-payloads waiting for the Configuration needed to decode them.
-The baseline reaction SHOULD be either reset or end the RTP session.
-</t>
-
-</section>
-
-</section>
-
-<section anchor="Comment Headers" title="Comment Headers">
-
-<t>
-With the Vorbis Data 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 payload 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
-payload 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="rfc1191"></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 consecutive
-fragments MUST be sent without any other payloads being sent between the first
-and the last fragment. The RTP payload 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 payloads, this will affect the
-RTCP jitter measurement. 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 payloads.
-Each of them 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 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 12345 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Ident | 1 | 0 | 0|
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-In this payload the initial sequence number is 1000 and the timestamp is 12345. 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 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 12345 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 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 this type of payloads.
-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 payload.
-</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 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 12345 |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | 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 payload. The Fragment type is set to 3 and the
-packet count remains set to 0. As in the previous payloads the timestamp remains
-set to the first payload timestamp 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 Vorbis fragments and decode the incomplete packet. If we use the
-fragmented Vorbis packet example above and the first RTP payload is lost the
-client MUST detect that the next RTP payload has the packet count field set
-to 0 and the Fragment type 2 and MUST drop it.
-The next RTP payload, which is the final fragmented packet, MUST be dropped
-in the same manner.
-If the missing RTP payload is the last, the received two fragments will be
-kept and the incomplete Vorbis packet decoded.
-</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="Type name:"> audio </t>
-<vspace blankLines="1" />
-
-<t hangText="Subtype name:"> vorbis </t>
-<vspace blankLines="1" />
-
-<t hangText="Required parameters:">
-
-<vspace blankLines="1" />
-
-<list style="hanging">
-<t hangText="rate:"> indicates the RTP timestamp clock rate as described in <xref target="rfc3551">RTP Profile for Audio and Video Conferences with Minimal Control.</xref>
-</t>
-<vspace blankLines="1" />
-
-<t hangText="channels:"> indicates the number of audio channels as described in <xref target="rfc3551">RTP Profile for Audio and Video Conferences with Minimal Control.</xref>
-</t>
-
-<vspace blankLines="1" />
-
-<t hangText="configuration:"> the <xref target="rfc3548">base64</xref> representation of the <xref target="Packed Headers">Packed Headers</xref>.
-</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 10 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]
-<vspace blankLines="1" />
-Ogg Vorbis I specification: Codec setup and packet decode. Available from the Xiph website, http://xiph.org
-</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" />
-
-Luca Barbato: <lu_zero at gentoo.org><br/>
-IETF Audio/Video Transport Working Group
-
-</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 delegated from the IESG</t>
-
-<vspace blankLines="1" />
-</list>
-
-<section anchor="Packed Headers IANA Considerations" title="Packed Headers IANA Considerations">
-
-<t>
-The following IANA considerations refers to the split configuration <xref target="Packed Headers">Packed Headers</xref> used within RFC XXXX.
-</t>
-
-<vspace blankLines="1" />
-
-<list style="hanging">
-<t hangText="Type name:"> audio </t>
-
-<vspace blankLines="1" />
-
-<t hangText="Subtype name:"> 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 10 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 delegated from the IESG</t>
-</list>
-
-</section>
-
-</section>
-
-<section anchor="SDP related considerations" title="SDP related considerations">
-<t>
-The following paragraphs define the mapping of the parameters described in the IANA considerations section and their usage in the <xref target="rfc3264">Offer/Answer Model</xref>. In order to be forward compatible the implementation MUST ignore unknown parameters.
-</t>
-
-<section anchor="Mapping Media Type Parameters into SDP" title="Mapping Media Type Parameters into SDP">
-
-<t>
-The information carried in the Media Type specification has a
-specific mapping to fields in the <xref target="rfc4566">Session Description
-Protocol (SDP)</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 type name ("audio") goes in SDP "m=" as the media name.</t>
-<vspace blankLines="1" />
-
-<t>The subtype name ("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 "configuration" MUST be included in the SDP
-"a=fmtp" attribute.</t>
-<vspace blankLines="1" />
-
-</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 port value is specified by the server application bound to the address
-specified in the c= line. The sample rate and channel count value specified
-in the rtpmap attribute SHOULD match the current Vorbis stream or considered
-the maximum number of channels to be expected and the least common multiple
-sample rate for the session. The Configuration payload delivers the exact
-information, thus the SDP information SHOULD be considered as a hint.
-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 URIs provided. The inline
-<xref target="rfc3548">base64</xref> configuration string is folded in this
-example due to RFC line length limitations.</t>
-
-<list style="empty">
-<t>c=IN IP4 192.0.2.1</t>
-<t>m=audio RTP/AVP 98</t>
-<t>a=rtpmap:98 vorbis/44100/2</t>
-<t>a=fmtp:98 configuration=AAAAAZ2f4g9NAh4aAXZvcmJpcwA...;</t>
-</list>
-</section>
-
-<t>
-Note that the payload format (encoding) names are commonly shown in upper case.
-Media Type subtypes are commonly shown in lower case. These names are
-case-insensitive in both places. Similarly, parameter names are
-case-insensitive both in Media Type types and in the default mapping to the SDP
-a=fmtp attribute. The a=fmtp line is a single line even if it is shown as multiple lines in this document for clarity.
-</t>
-
-</section>
-
-<section anchor="Usage with the SDP Offer/Answer Mode" title="Usage with the SDP Offer/Answer Model">
-
-<t>
-The are no negotiable parameters. All the of them are declarative.
-</t>
-
-</section>
-
-</section>
-<section anchor="Congestion Control" title="Congestion Control">
-<t>
- Vorbis clients SHOULD send regular receiver reports detailing
- congestion. A way to handle bandwidth changes MAY be redirect
- the client to a lower bitrate stream if one is available.
-</t>
-</section>
-<section anchor="Example" title="Example">
-
-<t>
-The following example shows a common usage pattern that MAY be applied in
-such situation, 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 webjockey'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 in-band method is unreliable, an out of band
-fallback is provided.</t>
-
-<t>The client may choose to fetch the Configuration from the alternate source
-as soon as it discovers a Configuration packet got lost in-band 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
-<xref target="rfc3550">RTP specification</xref>, the
-<xref target="rfc3548">base64 specification</xref> and the
-<xref target="rfc3986">URI Generic syntax specification</xref>.
-Among other considerations, this implies that the confidentiality of the
-media stream is archieved 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.
-</t>
-
-</section>
-<section title="Copying Conditions">
- <t>The authors agree to grant third parties the irrevocable right to copy,
- use and distribute the work, with or without modification, in any medium,
- without royalty, provided that, unless separate permission is granted,
- redistributed modified works do not contain misleading author, version,
- name of work, or endorsement information.</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 Media Type declaration is a
-continuation of draft-short-avt-rtp-vorbis-mime-00.txt.
-</t>
-
-<t>
-Thanks to the AVT, Vorbis Communities / Xiph.Org Foundation 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, Dario Gallucci, Juan Carlos De Martin.
-</t>
-
-</section>
-
-</middle>
-
-<back>
-
-<references title="Normative References">
-
-<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="STD" value="64"/>
-<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="STD" value="65"/>
-<seriesInfo name="RFC" value="3551" />
-</reference>
-
-<reference anchor="rfc3986">
-<front>
-<title abbrev="URI Generic Syntax">Uniform Resource Identifier (URI): Generic Syntax</title>
-<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
-</author>
-<author initials="R." surname="Fielding" fullname="Roy T. Fielding">
-</author>
-<author initials="L." surname="Masinter" fullname="Larry Masinter">
-</author>
-</front>
-<date year="2005" month="January" />
-<seriesInfo name="STD" value="66"/>
-<seriesInfo name="RFC" value="3986" />
-</reference>
-
-<reference anchor="rfc4566">
-<front>
-<title>SDP: Session Description Protocol</title>
-<author initials="M." surname="Handley" fullname="M. Handley">
-<organization /></author>
-<author initials="V." surname="Jacobson" fullname="V. Jacobson">
-<organization /></author>
-<author initials="C." surname="Perkins" fullname="C. Perkins">
-<organization /></author>
-<date year="2006" month="July" />
-</front>
-<seriesInfo name="RFC" value="4566" />
-<format type="TXT" octets="108820" target="ftp://ftp.isi.edu/in-notes/rfc4566.txt" />
-</reference>
-
-<reference anchor="rfc1191">
-<front>
-<title>Path MTU discovery</title>
-<author initials="J." surname="Mogul" fullname="Jeffrey Mogul">
-<organization>Digital Equipment Corporation (DEC) , Western Research Laboratory</organization>
-<address>
-<email>mogul at decwrl.dec.com</email></address></author>
-<author initials="S." surname="Deering" fullname="Steve Deering">
-<organization>Xerox Palo Alto Research Center</organization>
-<address>
-<email>deering at xerox.com</email></address></author>
-<date year="1990" day="1" month="November" />
-</front>
-<seriesInfo name="RFC" value="1191" />
-<format type="TXT" octets="47936" target="ftp://ftp.isi.edu/in-notes/rfc1191.txt" />
-</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="vorbis-spec-ref">
-<front>
-<title>Ogg Vorbis I specification: Codec setup and packet decode. Available from the Xiph website, http://xiph.org/vorbis/doc/Vorbis_I_spec.html</title>
-</front>
-</reference>
-
-</references>
-
-<references title="Informative 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="libvorbis">
-<front>
-<title>libvorbis: Available from the dedicated website, http://vorbis.com</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>
-<reference anchor="rfc4588">
-<front>
-<title>RTP Retransmission Payload Format</title>
-<author initials="J." surname="Rey" fullname="J. Rey">
-<organization /></author>
-<author initials="D." surname="Leon" fullname="D. Leon">
-<organization /></author>
-<author initials="A." surname="Miyazaki" fullname="A. Miyazaki">
-<organization /></author>
-<author initials="V." surname="Varsa" fullname="V. Varsa">
-<organization /></author>
-<author initials="R." surname="Hakenberg" fullname="R. Hakenberg">
-<organization /></author>
-<date year="2006" month="July" />
-</front>
-<seriesInfo name="RFC" value="4588" />
-<format type="TXT" octets="76630" target="ftp://ftp.isi.edu/in-notes/rfc4588.txt" />
-</reference>
-</references>
-</back>
-</rfc>
Added: trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-09.txt
===================================================================
--- trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-09.txt (rev 0)
+++ trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-09.txt 2008-01-14 19:17:32 UTC (rev 14399)
@@ -0,0 +1,1401 @@
+
+
+
+AVT Working Group L. Barbato
+Internet-Draft Xiph
+Expires: July 17, 2008 Jan 14, 2008
+
+
+ RTP Payload Format for Vorbis Encoded Audio
+ draft-ietf-avt-rtp-vorbis-09
+
+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 July 17, 2008.
+
+Copyright Notice
+
+ Copyright (C) The IETF Trust (2008).
+
+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 this memo are media type registrations, and the
+ details necessary for the use of Vorbis with the Session Description
+ Protocol (SDP).
+
+
+
+Barbato Expires July 17, 2008 [Page 1]
+
+Internet-Draft Vorbis RTP Payload Format Jan 2008
+
+
+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. Conformance and Document Conventions . . . . . . . . . . . 3
+ 2. Payload Format . . . . . . . . . . . . . . . . . . . . . . . . 3
+ 2.1. RTP Header . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 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 . . . . . . . . . . . . . . . . . 11
+ 3.2.1. Packed Headers . . . . . . . . . . . . . . . . . . . . 11
+ 3.3. Loss of Configuration Headers . . . . . . . . . . . . . . 12
+ 4. Comment Headers . . . . . . . . . . . . . . . . . . . . . . . 12
+ 5. Frame Packetization . . . . . . . . . . . . . . . . . . . . . 13
+ 5.1. Example Fragmented Vorbis Packet . . . . . . . . . . . . . 14
+ 5.2. Packet Loss . . . . . . . . . . . . . . . . . . . . . . . 16
+ 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
+ 6.1. Packed Headers IANA Considerations . . . . . . . . . . . . 18
+ 7. SDP related considerations . . . . . . . . . . . . . . . . . . 19
+ 7.1. Mapping Media Type Parameters into SDP . . . . . . . . . . 20
+ 7.1.1. SDP Example . . . . . . . . . . . . . . . . . . . . . 20
+ 7.2. Usage with the SDP Offer/Answer Model . . . . . . . . . . 21
+ 8. Congestion Control . . . . . . . . . . . . . . . . . . . . . . 21
+ 9. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
+ 9.1. Stream Radio . . . . . . . . . . . . . . . . . . . . . . . 21
+ 10. Security Considerations . . . . . . . . . . . . . . . . . . . 22
+ 11. Copying Conditions . . . . . . . . . . . . . . . . . . . . . . 22
+ 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22
+ 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
+ 13.1. Normative References . . . . . . . . . . . . . . . . . . . 22
+ 13.2. Informative References . . . . . . . . . . . . . . . . . . 23
+
+
+
+
+
+
+
+
+
+
+
+
+Barbato Expires July 17, 2008 [Page 2]
+
+Internet-Draft Vorbis RTP Payload Format Jan 2008
+
+
+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-4 AAC. 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 [11], 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. Conformance and Document Conventions
+
+ 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 BCP 14, [1] and
+ indicate requirement levels for compliant implementations.
+ Requirements apply to all implementations unless otherwise stated.
+
+ An implementation is a software module that supports one of the media
+ types defined in this document. Software modules may support
+ multiple media types, but conformance is considered individually for
+ each type.
+
+ Implementations that fail to satisfy one or more "MUST" requirements
+ are considered non-compliant. Implementations that satisfy all
+ "MUST" requirements, but fail to satisfy one or more "SHOULD"
+ requirements, are said to be "conditionally compliant". All other
+ implementations are "unconditionally compliant".
+
+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. There are 3 types of Vorbis data, an RTP
+ payload MUST contain just one of them at a time.
+
+
+
+
+
+Barbato Expires July 17, 2008 [Page 3]
+
+Internet-Draft Vorbis RTP Payload Format Jan 2008
+
+
+2.1. RTP Header
+
+ The format of the RTP header is specified in [2] and shown in Figure
+ Figure 1. This payload format uses the fields of the header in a
+ manner consistent with that specification.
+
+
+ 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 [2] and [3] 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 [2].
+
+ Extension (X): 1 bit
+
+ The Extension bit is used in accordance with [2].
+
+ CSRC count (CC): 4 bits
+
+ The CSRC count is used in accordance with [2].
+
+ Marker (M): 1 bit
+
+ Set to zero. Audio silence suppression not used. This conforms to
+ section 4.1 of [10].
+
+
+
+Barbato Expires July 17, 2008 [Page 4]
+
+Internet-Draft Vorbis RTP Payload Format Jan 2008
+
+
+ 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 [2].
+
+ Timestamp: 32 bits
+
+ A timestamp representing the sampling time of the first sample of the
+ first Vorbis packet in the RTP payload. The clock frequency MUST be
+ set to the sample rate of the encoded audio data and is conveyed out-
+ of-band (e.g. as an 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 [2].
+
+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. It is stored as network byte order integer.
+
+ Fragment type (F): 2 bits
+
+ This field is set according to the following list
+
+
+
+
+
+Barbato Expires July 17, 2008 [Page 5]
+
+Internet-Draft Vorbis RTP Payload Format Jan 2008
+
+
+ 0 = Not Fragmented
+ 1 = Start Fragment
+ 2 = Continuation Fragment
+ 3 = End Fragment
+
+ Vorbis Data Type (VDT): 2 bits
+
+ This field specifies the kind of Vorbis data stored in this RTP
+ packet. There are currently three different types of Vorbis
+ payloads. Each packet MUST contain only a single type of Vorbis
+ packet (e.g. you must not aggregate configuration and comment packets
+ in the same RTP payload)
+
+ 0 = Raw Vorbis payload
+ 1 = Vorbis Packed Configuration payload
+ 2 = Legacy Vorbis Comment payload
+ 3 = Reserved
+
+ The packets with a VDT 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 payload 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 [12] 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 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 in bytes of the following data
+ payload, followed by the raw Vorbis data padded to the nearest byte
+
+
+
+Barbato Expires July 17, 2008 [Page 6]
+
+Internet-Draft Vorbis RTP Payload Format Jan 2008
+
+
+ boundary, as explained by the vorbis specification [10]. The length
+ value is stored as network byte order integer.
+
+ 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 include the length field.
+
+ The payload packing of the Vorbis data packets MUST follow the
+ guidelines set-out in [3] where the oldest Vorbis packet occurs
+ immediately after the RTP packet header. Subsequent Vorbis packets,
+ if any, MUST follow in temporal order.
+
+ Channel mapping of the audio is in accordance with the Vorbis I
+ Specification [10].
+
+2.4. Example RTP Packet
+
+ Here is an example RTP payload containing two Vorbis 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
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | 2 |0|0| 0 |0| PT | sequence number |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | timestamp (in sample rate units) |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronisation source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Ident | 0 | 0 | 2 pks |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length | vorbis data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. vorbis data |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length | next vorbis packet data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. vorbis data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. vorbis data |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+
+
+
+Barbato Expires July 17, 2008 [Page 7]
+
+Internet-Draft Vorbis RTP Payload Format Jan 2008
+
+
+ Figure 4: Example Raw Vorbis Packet
+
+ 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.
+
+3. Configuration Headers
+
+ Unlike other mainstream audio codecs Vorbis has no statically
+ configured probability model. Instead, it packs all entropy decoding
+ configuration, Vector Quantization 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 [10] 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 typically 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 RTP stream.
+
+ For non chained streams, the recommended Configuration delivery
+ method is inline the Packed Configuration (Section 3.1.1) in the SDP
+ as explained in the IANA considerations (Section 7.1).
+
+ 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.
+
+
+
+Barbato Expires July 17, 2008 [Page 8]
+
+Internet-Draft Vorbis RTP Payload Format Jan 2008
+
+
+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 Vorbis Data Type. Clients MUST
+ be capable of dealing with fragmentation and periodic re-transmission
+ of [14] the configuration headers. The RTP timestamp value MUST
+ reflect the transmission time of the first data packet for which this
+ configuration applies.
+
+3.1.1. Packed Configuration
+
+ A Vorbis Packed Configuration is indicated with the Vorbis Data Type
+ field set to 1. Of the three headers defined in the Vorbis I
+ specification [10], the Identification and the Setup MUST be packed
+ as they are, while the comment header MAY be replaced with a dummy
+ one.
+
+ The packed configuration follows a generic way to store Xiph codec
+ configurations: The first field stores the number of the following
+ packets minus one (count field), the next ones represent the size of
+ the headers (length fields), the headers immediately follow the list
+ of length fields. The size of the last header is implicit.
+
+ The count and the length fields are encoded using the following
+ logic: the data is in network byte order, every byte has the most
+ significant bit used as flag and the following 7 used to store the
+ value. The first N bit are to be taken, where N is number of bits
+ needed to represent the value, taken modulo 7, and stored in the
+ first byte. If there are more bits, the flag bit is set to 1 and the
+ subsequent 7bit are stored in the following byte, if there are
+ remaining bits set the flag to 1 and the same procedure is repeated.
+ The ending byte has the flag bit set to 0. In order to decode it is
+ enough to iterate over the bytes until the flag bit set to 0, for
+ every byte the data is added to the accumulated value multiplied by
+ 128.
+
+ The headers are packed in the same order they are present in ogg:
+ Identification, Comment, Setup.
+
+ The 2 byte length tag defines the length of the packed headers as the
+ sum of the Configuration, Comment and Setup lengths.
+
+
+
+
+
+
+
+
+
+
+Barbato Expires July 17, 2008 [Page 9]
+
+Internet-Draft Vorbis RTP Payload Format Jan 2008
+
+
+ 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 | 1 | 0 | 0|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length | n. of headers | length1 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length2 | Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification | Comment ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment | Setup ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Setup ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Setup ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 5: 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.
+
+
+
+
+
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+
+Internet-Draft Vorbis RTP Payload Format Jan 2008
+
+
+3.2. Out of Band Transmission
+
+ The following packet definition 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 (network byte ordered) 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 6: Packed Headers Overview
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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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 ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. | n. of headers | length1 | length2 ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. | Identification Header ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .................................................................
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. | Comment Header ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .................................................................
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment Header |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Setup Header ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .................................................................
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Setup Header |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 7: Packed Headers Detail
+
+ The key difference between the in-band format and this one, is that
+ there is no need for the payload header octet. In this figure the
+ comment has a size bigger than 127 bytes.
+
+3.3. Loss of Configuration Headers
+
+ Unlike the loss of raw Vorbis payload data, loss of a configuration
+ header lead to a situation where it will not be possible to
+ successfully decode the stream. Implementations MAY try to recover
+ from error by requesting again the missing Configuration or, if the
+ delivery method is in-band, by buffering the payloads waiting for the
+ Configuration needed to decode them. The baseline reaction SHOULD be
+ either reset or end the RTP session.
+
+4. Comment Headers
+
+ With the Vorbis Data 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 [10].
+
+
+
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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 8: Comment Packet
+
+ The 2 bytes length field is necessary since this packet could be
+ fragmented.
+
+5. Frame Packetization
+
+ Each RTP payload 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 payload 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 consecutive fragments MUST be sent without any
+ other payloads being sent between the first and the last fragment.
+ The RTP payload 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
+
+
+
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+
+
+ the sequence number incremented as normal for the subsequent RTP
+ payloads, this will affect the RTCP jitter measurement. The length
+ field shows the fragment length.
+
+5.1. Example Fragmented Vorbis Packet
+
+ Here is an example fragmented Vorbis packet split over three RTP
+ payloads. Each of them 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 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | 12345 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Ident | 1 | 0 | 0|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length | vorbis data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. vorbis data |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 9: Example Fragmented Packet (Packet 1)
+
+ In this payload the initial sequence number is 1000 and the timestamp
+ is 12345. 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 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | 12345 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Ident | 2 | 0 | 0|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length | vorbis data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. vorbis data |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 10: 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 this
+ type of payloads. 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 payload.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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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 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | 12345 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Ident | 3 | 0 | 0|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length | vorbis data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. vorbis data |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 11: Example Fragmented Packet (Packet 3)
+
+ This is the last Vorbis fragment payload. The Fragment type is set
+ to 3 and the packet count remains set to 0. As in the previous
+ payloads the timestamp remains set to the first payload timestamp 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 Vorbis fragments and decode the
+ incomplete packet. If we use the fragmented Vorbis packet example
+ above and the first RTP payload is lost the client MUST detect that
+ the next RTP payload has the packet count field set to 0 and the
+ Fragment type 2 and MUST drop it. The next RTP payload, which is the
+ final fragmented packet, MUST be dropped in the same manner. If the
+ missing RTP payload is the last, the received two fragments will be
+ kept and the incomplete Vorbis packet decoded.
+
+ 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.
+
+
+
+
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+
+
+6. IANA Considerations
+
+ Type name: audio
+
+ Subtype name: vorbis
+
+ Required parameters:
+
+ rate: indicates the RTP timestamp clock rate as described in RTP
+ Profile for Audio and Video Conferences with Minimal Control.
+ [3]
+
+ channels: indicates the number of audio channels as described in
+ RTP Profile for Audio and Video Conferences with Minimal
+ Control. [3]
+
+ configuration: the base64 [9] representation of the Packed
+ Headers (Section 3.2.1).
+
+ Encoding considerations:
+
+ This media type is framed and contains binary data.
+
+ Security considerations:
+
+ See Section 10 of RFC XXXX.
+
+ Interoperability considerations:
+
+ None
+
+ 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://xiph.org
+
+ Applications which use this media type:
+
+ Audio streaming and conferencing tools
+
+ Additional information:
+
+ None
+
+
+
+
+
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+
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+
+
+ 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 [2]
+
+ Author:
+
+ Luca Barbato
+
+ Change controller:
+
+ IETF AVT Working Group delegated from the IESG
+
+
+6.1. Packed Headers IANA Considerations
+
+ The following IANA considerations refers to the split configuration
+ Packed Headers (Section 3.2.1) used within RFC XXXX.
+
+ Type name: audio
+
+ Subtype name: vorbis-config
+
+ Required parameters:
+
+ None
+
+ Optional parameters:
+
+ None
+
+ Encoding considerations:
+
+ This media type contains binary data.
+
+
+
+
+
+
+
+
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+
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+
+
+ Security considerations:
+
+ See Section 10 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
+
+ Restriction on usage:
+
+ This media type doesn't depend on the transport.
+
+ Author:
+
+ Luca Barbato
+
+ Change controller:
+
+ IETF AVT Working Group delegated from the IESG
+
+7. SDP related considerations
+
+ The following paragraphs define the mapping of the parameters
+ described in the IANA considerations section and their usage in the
+ Offer/Answer Model [8]. In order to be forward compatible the
+ implementation MUST ignore unknown parameters.
+
+
+
+
+
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+
+
+7.1. Mapping Media Type Parameters into SDP
+
+ The information carried in the 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 type name ("audio") goes in SDP "m=" as the media name.
+
+ o The subtype name ("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 "configuration" MUST be included in the
+ SDP "a=fmtp" 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 port value is specified by the server application bound to the
+ address specified in the c= line. The sample rate and channel count
+ value specified in the rtpmap attribute SHOULD match the current
+ Vorbis stream or considered the maximum number of channels to be
+ expected and the least common multiple sample rate for the session.
+ The Configuration payload delivers the exact information, thus the
+ SDP information SHOULD be considered as a hint. An example is found
+ below.
+
+7.1.1. 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 URIs provided. The inline
+ base64 [9] configuration string is folded in this example due to RFC
+ line length limitations.
+ c=IN IP4 192.0.2.1
+ m=audio RTP/AVP 98
+ a=rtpmap:98 vorbis/44100/2
+ a=fmtp:98 configuration=AAAAAZ2f4g9NAh4aAXZvcmJpcwA...;
+
+ Note that the payload format (encoding) names are commonly shown in
+ upper case. Media Type subtypes are commonly shown in lower case.
+ These names are case-insensitive in both places. Similarly,
+
+
+
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+
+
+ parameter names are case-insensitive both in Media Type types and in
+ the default mapping to the SDP a=fmtp attribute. The a=fmtp line is
+ a single line even if it is shown as multiple lines in this document
+ for clarity.
+
+7.2. Usage with the SDP Offer/Answer Model
+
+ The are no negotiable parameters. All the of them are declarative.
+
+8. Congestion Control
+
+ Vorbis clients SHOULD send regular receiver reports detailing
+ congestion. A way to handle bandwidth changes MAY be redirect the
+ client to a lower bitrate stream if one is available.
+
+9. Example
+
+ The following example shows a common usage pattern that MAY be
+ applied in such situation, the main scope of this section is to
+ explain better usage of the transmission vectors.
+
+9.1. 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 webjockey'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
+ 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 in-band method is
+ unreliable, an out of band fallback is provided.
+
+ The client may choose to fetch the Configuration from the alternate
+ source as soon as it discovers a Configuration packet got lost in-
+ band or use selective retransmission [13], 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
+
+
+
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+
+
+ 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.
+
+10. Security Considerations
+
+ RTP packets using this payload format are subject to the security
+ considerations discussed in the RTP specification [2], the base64
+ specification [9] and the URI Generic syntax specification [4].
+ Among other considerations, this implies that the confidentiality of
+ the media stream is archieved 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.
+
+11. Copying Conditions
+
+ The authors agree to grant third parties the irrevocable right to
+ copy, use and distribute the work, with or without modification, in
+ any medium, without royalty, provided that, unless separate
+ permission is granted, redistributed modified works do not contain
+ misleading author, version, name of work, or endorsement information.
+
+12. Acknowledgments
+
+ This document is a continuation of draft-moffitt-vorbis-rtp-00.txt
+ and draft-kerr-avt-vorbis-rtp-04.txt. The Media Type declaration is
+ a continuation of draft-short-avt-rtp-vorbis-mime-00.txt.
+
+ Thanks to the AVT, Vorbis Communities / Xiph.Org Foundation 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, Dario Gallucci, Juan
+ Carlos De Martin.
+
+13. References
+
+13.1. Normative References
+
+ [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
+ Levels", RFC 2119.
+
+ [2] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
+
+
+
+Barbato Expires July 17, 2008 [Page 22]
+
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+
+
+ "RTP: A Transport Protocol for real-time applications", STD 64,
+ RFC 3550.
+
+ [3] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
+ Conferences with Minimal Control.", STD 65, RFC 3551.
+
+ [4] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
+ Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986.
+
+ [5] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
+ Description Protocol", RFC 4566, July 2006.
+
+ [6] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
+ November 1990.
+
+ [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] "Ogg Vorbis I specification: Codec setup and packet decode.
+ Available from the Xiph website,
+ http://xiph.org/vorbis/doc/Vorbis_I_spec.html".
+
+13.2. Informative References
+
+ [11] Pfeiffer, S., "The Ogg Encapsulation Format Version 0",
+ RFC 3533.
+
+ [12] "libvorbis: Available from the dedicated website,
+ http://vorbis.com".
+
+ [13] Friedman, T., Caceres, R., and A. Clark, "RTP Control Protocol
+ Extended Reports (RTCP XR)", RFC 3611, November 2003.
+
+ [14] Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R. Hakenberg,
+ "RTP Retransmission Payload Format", RFC 4588, July 2006.
+
+
+
+
+
+
+
+
+
+
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+
+
+Author's Address
+
+ Luca Barbato
+ Xiph.Org Foundation
+
+ EMail: lu_zero at gentoo.org
+ URI: http://xiph.org/
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2008).
+
+ 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.
+
+ 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, THE IETF TRUST 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.
+
+Intellectual Property
+
+ 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.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is provided by the IETF
+ Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Barbato Expires July 17, 2008 [Page 25]
+
+
Copied: trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-09.xml (from rev 14398, trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-08.xml)
===================================================================
--- trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-09.xml (rev 0)
+++ trunk/vorbis/doc/draft-ietf-avt-rtp-vorbis-09.xml 2008-01-14 19:17:32 UTC (rev 14399)
@@ -0,0 +1,1352 @@
+<?xml version="1.0"?>
+<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
+<?rfc toc="yes" ?>
+<?rfc compact="yes" ?>
+<?rfc rfcedstyle="yes" ?>
+
+<rfc ipr="full3978" docName="draft-ietf-avt-rtp-vorbis-09">
+
+<front>
+<title abbrev="Vorbis RTP Payload Format">RTP Payload Format for Vorbis Encoded Audio</title>
+
+<author initials="L" surname="Barbato" fullname="Luca Barbato">
+<organization abbrev="Xiph">Xiph.Org Foundation</organization>
+<address>
+<email>lu_zero at gentoo.org</email>
+<uri>http://xiph.org/</uri>
+</address>
+</author>
+
+<date day="14" month="Jan" year="2008" />
+
+<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 this memo are media type registrations, and the details
+necessary for the use of Vorbis with the 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-4 AAC.
+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="Conformance and Document Conventions">
+
+<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 BCP 14, <xref target="rfc2119"/> and indicate requirement levels for compliant implementations. Requirements apply to all implementations unless otherwise stated.</t>
+<t>An implementation is a software module that supports one of the media types defined in this document. Software modules may support multiple media types, but conformance is considered individually for each type.</t>
+<t>Implementations that fail to satisfy one or more "MUST" requirements are considered non-compliant. Implementations that satisfy all "MUST" requirements, but fail to satisfy one or more "SHOULD" requirements, are said to be "conditionally compliant". All other implementations are "unconditionally compliant".</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. There are 3 types of Vorbis
+data, an RTP payload MUST contain just one of them at a time.
+</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 payload. The clock frequency MUST be set to the sample
+rate of the encoded audio data and is conveyed out-of-band (e.g. as an 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. It is stored as network byte order integer.
+</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 specifies the kind of Vorbis data stored in this RTP packet. There
+are currently three different types of Vorbis payloads. Each packet MUST contain only a single type of Vorbis packet (e.g. you must not aggregate configuration and comment packets in the same RTP payload)
+</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 VDT 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
+payload 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 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 in bytes of the following data payload, followed by the
+raw Vorbis data padded to the nearest byte boundary, as explained by the <xref target="vorbis-spec-ref">vorbis specification</xref>. The length value is stored
+as network byte order integer.
+</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 include 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 Vorbis packet occurs
+immediately after the RTP packet header. Subsequent Vorbis 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 payload containing two Vorbis packets.
+</t>
+
+<figure anchor="Example Raw Vorbis Packet" title="Example Raw Vorbis 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
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | 2 |0|0| 0 |0| PT | sequence number |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | timestamp (in sample rate units) |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronisation source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Ident | 0 | 0 | 2 pks |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length | vorbis data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. vorbis data |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length | next vorbis packet data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. vorbis 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, Vector Quantization 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 typically 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 RTP stream.
+</t>
+
+<!--
+<t>
+The delivery vectors in use can be 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.
+-->
+<t>For non chained streams, the recommended Configuration delivery
+method is inline the <xref target="Packed Configuration">Packed Configuration</xref> in the SDP as explained in the <xref target="Mapping Media Type Parameters into SDP"> IANA considerations</xref>.
+</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 Vorbis Data Type.
+Clients MUST be capable of dealing with fragmentation and periodic
+<xref target="rfc4588">re-transmission of</xref> the configuration headers.
+The RTP timestamp value MUST reflect the transmission time of the first data packet for which this configuration applies.
+</t>
+
+<section anchor="Packed Configuration" title="Packed Configuration">
+
+<t>
+A Vorbis Packed Configuration is indicated with the Vorbis Data 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 MUST be packed as they are, while the comment
+header MAY be replaced with a dummy one.</t>
+<t>
+The packed configuration follows a generic way to store Xiph codec
+configurations: The first field stores the number of the following packets
+minus one (count field), the next ones represent the size of the headers
+(length fields), the headers immediately follow the list of length fields.
+The size of the last header is implicit.</t>
+<t>
+The count and the length fields are encoded using the following logic: the data
+is in network byte order, every byte has the most significant bit used as flag
+and the following 7 used to store the value.
+The first N bit are to be taken, where N is number of bits needed to represent
+the value, taken modulo 7, and stored in the first byte.
+If there are more bits, the flag bit is set to 1 and the subsequent 7bit are
+stored in the following byte, if there are remaining bits set the flag to 1 and
+the same procedure is repeated.
+The ending byte has the flag bit set to 0. In order to decode it is enough to
+iterate over the bytes until the flag bit set to 0, for every byte the data is
+added to the accumulated value multiplied by 128.</t>
+<t>
+The headers are packed in the same order they are present in ogg:
+Identification, Comment, Setup.</t>
+
+<t>
+The 2 byte length tag defines the length of the packed headers as the sum of
+the Configuration, Comment and Setup lengths.</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 | 1 | 0 | 0|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length | n. of headers | length1 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length2 | Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification | Comment ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment | 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>
+The following packet definition 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 (network byte ordered) 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>
+
+<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 ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. | n. of headers | length1 | length2 ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. | Identification Header ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .................................................................
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. | Comment Header ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .................................................................
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment Header |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Setup Header ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .................................................................
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Setup Header |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+<t>
+The key difference between the in-band format and this one, is that there is no
+need for the payload header octet. In this figure the comment has a size bigger
+than 127 bytes.
+</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
+lead to a situation where it will not be possible to successfully decode the
+stream. Implementations MAY try to recover from error by requesting again the
+missing Configuration or, if the delivery method is in-band, by buffering the
+payloads waiting for the Configuration needed to decode them.
+The baseline reaction SHOULD be either reset or end the RTP session.
+</t>
+
+</section>
+
+</section>
+
+<section anchor="Comment Headers" title="Comment Headers">
+
+<t>
+With the Vorbis Data 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 payload 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
+payload 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="rfc1191"></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 consecutive
+fragments MUST be sent without any other payloads being sent between the first
+and the last fragment. The RTP payload 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 payloads, this will affect the
+RTCP jitter measurement. 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 payloads.
+Each of them 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 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | 12345 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Ident | 1 | 0 | 0|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length | vorbis data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. vorbis data |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+
+<t>
+In this payload the initial sequence number is 1000 and the timestamp is 12345. 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 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | 12345 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | 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 this type of payloads.
+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 payload.
+</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 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | 12345 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | 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 payload. The Fragment type is set to 3 and the
+packet count remains set to 0. As in the previous payloads the timestamp remains
+set to the first payload timestamp 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 Vorbis fragments and decode the incomplete packet. If we use the
+fragmented Vorbis packet example above and the first RTP payload is lost the
+client MUST detect that the next RTP payload has the packet count field set
+to 0 and the Fragment type 2 and MUST drop it.
+The next RTP payload, which is the final fragmented packet, MUST be dropped
+in the same manner.
+If the missing RTP payload is the last, the received two fragments will be
+kept and the incomplete Vorbis packet decoded.
+</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="Type name:"> audio </t>
+<vspace blankLines="1" />
+
+<t hangText="Subtype name:"> vorbis </t>
+<vspace blankLines="1" />
+
+<t hangText="Required parameters:">
+
+<vspace blankLines="1" />
+
+<list style="hanging">
+<t hangText="rate:"> indicates the RTP timestamp clock rate as described in <xref target="rfc3551">RTP Profile for Audio and Video Conferences with Minimal Control.</xref>
+</t>
+<vspace blankLines="1" />
+
+<t hangText="channels:"> indicates the number of audio channels as described in <xref target="rfc3551">RTP Profile for Audio and Video Conferences with Minimal Control.</xref>
+</t>
+
+<vspace blankLines="1" />
+
+<t hangText="configuration:"> the <xref target="rfc3548">base64</xref> representation of the <xref target="Packed Headers">Packed Headers</xref>.
+</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 10 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]
+<vspace blankLines="1" />
+Ogg Vorbis I specification: Codec setup and packet decode. Available from the Xiph website, http://xiph.org
+</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" />
+
+Luca Barbato: <lu_zero at gentoo.org><br/>
+IETF Audio/Video Transport Working Group
+
+</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 delegated from the IESG</t>
+
+<vspace blankLines="1" />
+</list>
+
+<section anchor="Packed Headers IANA Considerations" title="Packed Headers IANA Considerations">
+
+<t>
+The following IANA considerations refers to the split configuration <xref target="Packed Headers">Packed Headers</xref> used within RFC XXXX.
+</t>
+
+<vspace blankLines="1" />
+
+<list style="hanging">
+<t hangText="Type name:"> audio </t>
+
+<vspace blankLines="1" />
+
+<t hangText="Subtype name:"> 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 10 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 delegated from the IESG</t>
+</list>
+
+</section>
+
+</section>
+
+<section anchor="SDP related considerations" title="SDP related considerations">
+<t>
+The following paragraphs define the mapping of the parameters described in the IANA considerations section and their usage in the <xref target="rfc3264">Offer/Answer Model</xref>. In order to be forward compatible the implementation MUST ignore unknown parameters.
+</t>
+
+<section anchor="Mapping Media Type Parameters into SDP" title="Mapping Media Type Parameters into SDP">
+
+<t>
+The information carried in the Media Type specification has a
+specific mapping to fields in the <xref target="rfc4566">Session Description
+Protocol (SDP)</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 type name ("audio") goes in SDP "m=" as the media name.</t>
+<vspace blankLines="1" />
+
+<t>The subtype name ("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 "configuration" MUST be included in the SDP
+"a=fmtp" attribute.</t>
+<vspace blankLines="1" />
+
+</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 port value is specified by the server application bound to the address
+specified in the c= line. The sample rate and channel count value specified
+in the rtpmap attribute SHOULD match the current Vorbis stream or considered
+the maximum number of channels to be expected and the least common multiple
+sample rate for the session. The Configuration payload delivers the exact
+information, thus the SDP information SHOULD be considered as a hint.
+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 URIs provided. The inline
+<xref target="rfc3548">base64</xref> configuration string is folded in this
+example due to RFC line length limitations.</t>
+
+<list style="empty">
+<t>c=IN IP4 192.0.2.1</t>
+<t>m=audio RTP/AVP 98</t>
+<t>a=rtpmap:98 vorbis/44100/2</t>
+<t>a=fmtp:98 configuration=AAAAAZ2f4g9NAh4aAXZvcmJpcwA...;</t>
+</list>
+</section>
+
+<t>
+Note that the payload format (encoding) names are commonly shown in upper case.
+Media Type subtypes are commonly shown in lower case. These names are
+case-insensitive in both places. Similarly, parameter names are
+case-insensitive both in Media Type types and in the default mapping to the SDP
+a=fmtp attribute. The a=fmtp line is a single line even if it is shown as multiple lines in this document for clarity.
+</t>
+
+</section>
+
+<section anchor="Usage with the SDP Offer/Answer Mode" title="Usage with the SDP Offer/Answer Model">
+
+<t>
+The are no negotiable parameters. All the of them are declarative.
+</t>
+
+</section>
+
+</section>
+<section anchor="Congestion Control" title="Congestion Control">
+<t>
+ Vorbis clients SHOULD send regular receiver reports detailing
+ congestion. A way to handle bandwidth changes MAY be redirect
+ the client to a lower bitrate stream if one is available.
+</t>
+</section>
+<section anchor="Example" title="Example">
+
+<t>
+The following example shows a common usage pattern that MAY be applied in
+such situation, 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 webjockey'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 in-band method is unreliable, an out of band
+fallback is provided.</t>
+
+<t>The client may choose to fetch the Configuration from the alternate source
+as soon as it discovers a Configuration packet got lost in-band 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
+<xref target="rfc3550">RTP specification</xref>, the
+<xref target="rfc3548">base64 specification</xref> and the
+<xref target="rfc3986">URI Generic syntax specification</xref>.
+Among other considerations, this implies that the confidentiality of the
+media stream is archieved 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.
+</t>
+
+</section>
+<section title="Copying Conditions">
+ <t>The authors agree to grant third parties the irrevocable right to copy,
+ use and distribute the work, with or without modification, in any medium,
+ without royalty, provided that, unless separate permission is granted,
+ redistributed modified works do not contain misleading author, version,
+ name of work, or endorsement information.</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 Media Type declaration is a
+continuation of draft-short-avt-rtp-vorbis-mime-00.txt.
+</t>
+
+<t>
+Thanks to the AVT, Vorbis Communities / Xiph.Org Foundation 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, Dario Gallucci, Juan Carlos De Martin.
+</t>
+
+</section>
+
+</middle>
+
+<back>
+
+<references title="Normative References">
+
+<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="STD" value="64"/>
+<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="STD" value="65"/>
+<seriesInfo name="RFC" value="3551" />
+</reference>
+
+<reference anchor="rfc3986">
+<front>
+<title abbrev="URI Generic Syntax">Uniform Resource Identifier (URI): Generic Syntax</title>
+<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
+</author>
+<author initials="R." surname="Fielding" fullname="Roy T. Fielding">
+</author>
+<author initials="L." surname="Masinter" fullname="Larry Masinter">
+</author>
+</front>
+<date year="2005" month="January" />
+<seriesInfo name="STD" value="66"/>
+<seriesInfo name="RFC" value="3986" />
+</reference>
+
+<reference anchor="rfc4566">
+<front>
+<title>SDP: Session Description Protocol</title>
+<author initials="M." surname="Handley" fullname="M. Handley">
+<organization /></author>
+<author initials="V." surname="Jacobson" fullname="V. Jacobson">
+<organization /></author>
+<author initials="C." surname="Perkins" fullname="C. Perkins">
+<organization /></author>
+<date year="2006" month="July" />
+</front>
+<seriesInfo name="RFC" value="4566" />
+<format type="TXT" octets="108820" target="ftp://ftp.isi.edu/in-notes/rfc4566.txt" />
+</reference>
+
+<reference anchor="rfc1191">
+<front>
+<title>Path MTU discovery</title>
+<author initials="J." surname="Mogul" fullname="Jeffrey Mogul">
+<organization>Digital Equipment Corporation (DEC) , Western Research Laboratory</organization>
+<address>
+<email>mogul at decwrl.dec.com</email></address></author>
+<author initials="S." surname="Deering" fullname="Steve Deering">
+<organization>Xerox Palo Alto Research Center</organization>
+<address>
+<email>deering at xerox.com</email></address></author>
+<date year="1990" day="1" month="November" />
+</front>
+<seriesInfo name="RFC" value="1191" />
+<format type="TXT" octets="47936" target="ftp://ftp.isi.edu/in-notes/rfc1191.txt" />
+</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="vorbis-spec-ref">
+<front>
+<title>Ogg Vorbis I specification: Codec setup and packet decode. Available from the Xiph website, http://xiph.org/vorbis/doc/Vorbis_I_spec.html</title>
+</front>
+</reference>
+
+</references>
+
+<references title="Informative 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="libvorbis">
+<front>
+<title>libvorbis: Available from the dedicated website, http://vorbis.com</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>
+<reference anchor="rfc4588">
+<front>
+<title>RTP Retransmission Payload Format</title>
+<author initials="J." surname="Rey" fullname="J. Rey">
+<organization /></author>
+<author initials="D." surname="Leon" fullname="D. Leon">
+<organization /></author>
+<author initials="A." surname="Miyazaki" fullname="A. Miyazaki">
+<organization /></author>
+<author initials="V." surname="Varsa" fullname="V. Varsa">
+<organization /></author>
+<author initials="R." surname="Hakenberg" fullname="R. Hakenberg">
+<organization /></author>
+<date year="2006" month="July" />
+</front>
+<seriesInfo name="RFC" value="4588" />
+<format type="TXT" octets="76630" target="ftp://ftp.isi.edu/in-notes/rfc4588.txt" />
+</reference>
+</references>
+</back>
+</rfc>
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