[xiph-commits] r10499 - trunk/vorbis/doc
lu_zero at svn.xiph.org
lu_zero at svn.xiph.org
Tue Nov 29 10:54:47 PST 2005
Author: lu_zero
Date: 2005-11-29 10:54:43 -0800 (Tue, 29 Nov 2005)
New Revision: 10499
Modified:
trunk/vorbis/doc/draft-ietf-avt-vorbis-rtp-00.xml
Log:
Back to the drawing board
Modified: trunk/vorbis/doc/draft-ietf-avt-vorbis-rtp-00.xml
===================================================================
--- trunk/vorbis/doc/draft-ietf-avt-vorbis-rtp-00.xml 2005-11-29 03:06:03 UTC (rev 10498)
+++ trunk/vorbis/doc/draft-ietf-avt-vorbis-rtp-00.xml 2005-11-29 18:54:43 UTC (rev 10499)
@@ -3,20 +3,20 @@
<?rfc toc="yes" ?>
<?rfc compact='yes'?>
-<rfc ipr="full3667" docName="RTP Payload Format for Vorbis Encoded Audio">
+<rfc ipr="full3978" docName="RTP Payload Format for Vorbis Encoded Audio">
<front>
-<title>draft-ietf-avt-vorbis-rtp-00</title>
+<title>draft-kerr-avt-vorbis-rtp-05</title>
-<author initials="P" surname="Kerr" fullname="Phil Kerr">
+<author initials="L" surname="Barbato" fullname="Luca Barbato">
<organization>Xiph.Org</organization>
<address>
-<email>phil at plus24.com</email>
+<email>lu_zero at gentoo.org</email>
<uri>http://www.xiph.org/</uri>
</address>
</author>
-<date day="31" month="January" year="2005" />
+<date day="21" month="October" year="2005" />
<area>General</area>
<workgroup>AVT Working Group</workgroup>
@@ -27,13 +27,12 @@
<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, metadata and other setup information.</t>
+<t>
+This document describes an RTP payload format for transporting Vorbis encoded audio. It details the RTP encapsulation mechanism for raw Vorbis data and details the delivery mechanisms for the decoder probability model, referred to as a codebook and other setup information.
+</t>
<t>
-Also included within the document are the necessary details for the use of Vorbis with MIME and Session Description Protocol
-(SDP).
+Also included within the document are the necessary details for the use of Vorbis with MIME and Session Description Protocol (SDP).
</t>
</abstract>
@@ -51,12 +50,17 @@
<section anchor="Introduction" title="Introduction">
<t>
-Vorbis is a general purpose perceptual audio codec intended to allow maximum encoder flexibility, thus allowing it to scale
-competitively over an exceptionally wide range of bitrates. At the high quality/bitrate end of the scale (CD or DAT rate
-stereo, 16/24 bits), it is in the same league as MPEG-2 and MPC. Similarly, the 1.0 encoder can encode high-quality CD and
-DAT rate stereo at below 48k bits/sec without resampling to a lower rate. Vorbis is also intended for lower and higher sample
-rates (from 8kHz telephony to 192kHz digital masters) and a range of channel representations (monaural, polyphonic, stereo,
-quadraphonic, 5.1, ambisonic, or up to 255 discrete channels).
+Vorbis is a general purpose perceptual audio codec intended to allow
+maximum encoder flexibility, thus allowing it to scale competitively
+over an exceptionally wide range of bitrates. At the high
+quality/bitrate end of the scale (CD or DAT rate stereo, 16/24 bits), it
+is in the same league as MPEG-2 and MPC.
+Similarly, the version 1.1 reference encoder can encode high-quality CD
+and DAT rate stereo at below 48k bits/sec without resampling to a lower
+rate. Vorbis is also intended for lower and higher sample rates (from
+8kHz telephony to 192kHz digital masters) and a range of channel
+representations (monaural, polyphonic, stereo, quadraphonic, 5.1,
+ambisonic, or up to 255 discrete channels).
</t>
<t>
@@ -78,16 +82,13 @@
<section anchor="Payload Format" title="Payload Format">
<t>
-For RTP based transportation of Vorbis encoded audio the standard RTP header is followed by a 5 octet payload header, then the
-payload data. The payload headers are used to associate the Vorbis data with its associated decoding codebooks as well as
-indicating if the following packet contains fragmented Vorbis data and/or the the number of whole Vorbis data frames. The
-payload data contains the raw Vorbis bitstream information.
+For RTP based transportation of Vorbis encoded audio the standard RTP header is followed by a 4 octet payload header, then the payload data. The payload headers are used to associate the Vorbis data with its associated decoding codebooks as well as indicating if the following packet contains fragmented Vorbis data and/or the the number of whole Vorbis data frames. The payload data contains the raw Vorbis bitstream information.
</t>
<section anchor="RTP Header" title="RTP Header">
<t>
-The format of the RTP header is specified in <xref target="rfc3550"></xref> and shown in Figure 1. This payload format uses the fields of the header in a manner consistent with that specification.
+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>
@@ -177,8 +178,7 @@
<section anchor="Payload Header" title="Payload Header">
<t>
-After the RTP Header section the following five octets are the Payload Header. This header is split into a number of bitfields
-detailing the format of the following payload data packets.
+After the RTP Header section the following 4 octets are the Payload Header. This header is split into a number of bitfields detailing the format of the following payload data packets.
</t>
<figure anchor="Payload Header Figure" title="Payload Header">
@@ -186,49 +186,46 @@
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
+ | Ident | F |VDT|# pkts.|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |C|F|VDT|# pkts.|
- +-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
<t>
-Codebook Ident: 32 bits</t>
+Ident: 24 bits</t>
<t>
-This 32 bit field is used to associate the Vorbis data to a decoding Codebook. It is created by making a CRC32 checksum
-of the codebook required to decode the particular Vorbis audio stream.
+This 24 bit field is used to associate the Vorbis data to a decoding Configuration.
</t>
<t>
-Continuation (C): 1 bit</t>
+Fragment type (F): 2 bits</t>
<t>
-Set to one if this is a continuation of a fragmented packet.
+This field is set accordingly the following list
</t>
+<vspace blankLines="1" />
+<list style="empty">
+<t> 0 = Not Fragmented</t>
+<t> 1 = Start Fragment</t>
+<t> 2 = Continuation Fragment</t>
+<t> 3 = End Fragment</t>
+</list>
<t>
-Fragmented (F): 1 bit</t>
-<t>
-Set to one if the payload contains complete packets or if it contains the last fragment of a fragmented packet.
-</t>
-
-<t>
Vorbis Data Type (VDT): 2 bits</t>
<t>
-This field sets the packet payload type for the Vorbis data. There are currently four type of Vorbis payloads.
+This field sets the packet payload type for the Vorbis data. There are currently three type of Vorbis payloads.
</t>
<vspace blankLines="1" />
<list style="empty">
<t> 0 = Raw Vorbis payload</t>
-<t> 1 = Vorbis Setup payload</t>
-<t> 2 = Vorbis Codebook payload</t>
-<t> 3 = Vorbis Metadata payload</t>
+<t> 1 = Vorbis Packed Configuration payload</t>
+<t> 2 = Legacy Vorbis Comment payload</t>
+<t> 3 = Reserved</t>
</list>
<t>
-The last 4 bits are the number of complete packets in this payload. This provides for a maximum number of 15 Vorbis
-packets in the payload. If the packet contains fragmented data the number of packets MUST be set to 0.
+The last 4 bits are the number of complete packets in this payload. This provides for a maximum number of 15 Vorbis packets in the payload. If the packet contains fragmented data the number of packets MUST be set to 0.
</t>
</section>
@@ -236,11 +233,7 @@
<section anchor="Payload Data" title="Payload Data">
<t>
-Raw Vorbis packets are unbounded in length currently, although at some future point there will likely be a practical
-limit placed on them. Typical Vorbis packet sizes are from very small (2-3 bytes) to quite large (8-12 kilobytes).
-The reference implementation <xref target="libvorbis"></xref> typically produces packets less than ~800 bytes, except for the
-codebook header packets which are ~4-12 kilobytes. Within an RTP context the maximum Vorbis packet size, including the
-RTP and payload headers, SHOULD be kept below the path MTU to avoid packet fragmentation.
+Raw Vorbis packets are unbounded in length currently, although at some future point there will likely be a practical limit placed on them. Typical Vorbis packet sizes are from very small (2-3 bytes) to quite large (8-12 kilobytes). The reference implementation <xref target="libvorbis"></xref> typically produces packets less than ~800 bytes, except for the setup header packets which are ~4-12 kilobytes. Within an RTP context the maximum packet size, including the RTP and payload headers, SHOULD be kept below the path MTU to avoid packet fragmentation.
</t>
<figure anchor="Payload Data Figure" title="Payload Data Header">
@@ -254,13 +247,11 @@
</figure>
<t>
-Each Vorbis payload packet starts with a two octet length header, which is used to represent the size of the following
-data payload, followed by the raw Vorbis data.
+Each Vorbis payload packet starts with a two octet length header, which is used to represent the size of the following data payload, followed by the raw Vorbis data padded to the nearest byte boundary.
</t>
<t>
-For payloads which consist of multiple Vorbis packets the payload data consists of the packet length followed by the
-packet data for each of the Vorbis packets in the payload.
+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>
@@ -268,12 +259,11 @@
</t>
<t>
-The payload packing of the Vorbis data packets SHOULD follow the guidelines set-out in <xref target="rfc3551"></xref>
-where the oldest packet occurs immediately after the RTP packet header.
+The payload packing of the Vorbis data packets MUST follow the guidelines set-out in <xref target="rfc3551"></xref> where the oldest packet occurs immediately after the RTP packet header.
</t>
<t>
-Channel mapping of the audio is in accordance with BS. 775-1 ITU-R <xref target="775itu"></xref>.
+Channel mapping of the audio is in accordance with the <xref target="vorbis-spec-ref">Vorbis I Specification</xref>.
</t>
</section>
@@ -314,9 +304,9 @@
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
+ | Ident | 0 | 0 | 2 pks |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|1| 0 | 2 pks | length | vorbis data ..
+ | length | vorbis data ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
.. vorbis data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
@@ -328,49 +318,74 @@
</figure>
<t>
-The payload data section of the RTP packet starts with the 32 bit Codebook Ident field followed by the one octet
-configuration header, which has the number of Vorbis frames set to 2. Each of the Vorbis data frames is prefixed by the two
-octet length field.
+The payload data section of the RTP packet starts with the 24 bit Ident field followed by the one octet bitfield header, which has the number of Vorbis frames set to 2. Each of the Vorbis data frames is prefixed by the two octet length field. The Packet Type and Fragment Type are set to 0. The decode Configuration that will be used to decode the packets is the one indexed by the ident value.
</t>
</section>
</section>
-<section anchor="Frame Packetizing" title="Frame Packetizing">
+
+<section anchor="Configuration Headers" title="Configuration Headers">
+
<t>
-Each RTP packet contains either one complete Vorbis packet, one Vorbis packet fragment, or an integer number of complete Vorbis
-packets (up to a max of 15 packets, since the number of packets is defined by a 4 bit value).
+Unlike other mainstream audio codecs Vorbis has no statically
+configured probability model. Instead, it packs all entropy decoding
+configuration, VQ and Huffman models into a data block that must be
+transmitted to the decoder along with the compressed data. A decoder
+also requires identification information detailing the number of audio
+channels, bitrates and other information to configure itself for a
+particular compressed data stream. These two blocks of information are
+often referred to collectively as the "codebooks" for a Vorbis stream,
+and are nominally included as special "header" packets at the start
+of the compressed data.
</t>
<t>
-Any Vorbis data packet that is less than path MTU SHOULD be bundled in the RTP packet with as many Vorbis packets as will
-fit, up to a maximum of 15. Path MTU is detailed in <xref target="rfc1063"></xref> and <xref target="rfc1981"></xref>.
+Thus these two codebook header packets must be received by the decoder
+before any audio data can be interpreted. In addition,
+the <xref target="vorbis-spec-ref">Vorbis I specification</xref>
+requires the presense of a comment header packet which gives simple
+metadata about the stream. This requirement poses problems in RTP,
+which is often used over unreliable transports.
</t>
<t>
-If a Vorbis packet is larger than 65535 octets it MUST be fragmented. A fragmented packet has a zero in the last four bits
-of the payload header. Each fragment after the first will also set the Continued (C) bit to one in the payload header. The
-RTP packet containing the last fragment of the Vorbis packet will have the Fragmented (F) bit set to one. To maintain the
-correct sequence for fragmented packet reception the timestamp field of fragmented packets MUST be the same as the first
-packet sent, with the sequence number incremented as normal for the subsequent RTP packets.
+Since this information must be transmitted reliably and, as the RTP
+stream may change certain configuration data mid-session, there are
+different methods for delivering this configuration data to a
+client, both in-band and out-of-band which is detailed below. SDP
+delivery is used to setup an initial state for the client application.
+The changes may be due to different codebooks as well as different
+bitrates of the stream.
</t>
-<section anchor="Example Fragmented Vorbis Packet" title="Example Fragmented Vorbis Packet">
+<t>
+The delivery vectors in use are specified by an SDP attribute to indicate the method and the optional URI where the Vorbis <xref target="Packed Configuration">Packed Configuration</xref> Packets could be fetched. Different delivery methods MAY be advertised for the same session. The in-band Configuration delivery SHOULD be considered as baseline, out-of-band delivery methods that don't use RTP will not be described in this document. For non chained streams, the Configuration delivery method RECOMMENDED is inline the <xref target="Packed Configuration">Packed Configuration</xref> in the SDP as explained in the <xref target="Mapping MIME Parameters into SDP"> IANA considerations</xref> section.
+</t>
<t>
-Here is an example fragmented Vorbis packet split over three RTP packets. Each packet contains the standard RTP headers as
-well as the 5 octet Vorbis headers.
+The 24 bit Ident field is used to map which Configuration will be used to decodea packet. When the Ident field changes, it indicates that a change in the stream has taken place. The client application MUST have in advance the correct configuration and if the client detects a change in the Ident value and does not have this information it MUST NOT decode the raw Vorbis data associated until it fetches the correct Configuration.
</t>
-<figure anchor="Example Fragmented Packet (Packet 1)" title="Example Fragmented Packet (Packet 1)">
-<artwork><![CDATA[
- Packet 1:
+<section anchor="In-band Header Transmission" title="In-band Header Transmission">
+<t>
+The <xref target="Packed Configuration">Packed Configuration</xref> Payload is sent in-band with the packet type bits set to match the payload type. Clients MUST be capable of dealing with fragmentation and periodic re-transmission of the configuration headers.
+</t>
+
+<section anchor="Packed Configuration" title="Packed Configuration">
+
+<t>
+A Vorbis Packed Configuration is indicated with the payload type field set to 1. Of the three headers, defined in the <xref target="vorbis-spec-ref">Vorbis I specification</xref>, the identification and the setup will be packed together, the comment header is completely suppressed. Is up to the client provide a minimal size comment header to the decoder if required by the implementation.
+</t>
+
+<figure anchor="Packed Configuration Figure" title="Packed Configuration Figure">
+<artwork><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1000 |
+ |V=2|P|X| CC |M| PT | xxxx |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| xxxxx |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
@@ -380,220 +395,178 @@
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
+ | Ident | 0 | 1 | 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|0| 0 | 0| length | vorbis data ..
+ | length | Identification ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
+ .. Identification ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. | Setup ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Setup ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Setup |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
+<t>The Ident field is set with the value that will be used by the Raw Payload Packets to address this Configuration. The Fragment type is set to 0 since the packet bears the full Packed configuration, the number of packet is set to 1.</t>
+</section>
+</section>
+
+<section anchor="Out of Band Transmission" title="Out of Band Transmission">
+
+
<t>
-In this packet the initial sequence number is 1000 and the timestamp is xxxxx. The Continuation (C) bit is set to one,
-indicating it is not the continuation of a fragmented bit, and the Fragmentation (F) is set to 0 indicating it is a fragmented
-packet. The number of packets field is set to 0, and as the payload is raw Vorbis data the VDT field is set to 0.
+This section, as stated before, won't cover all the possible out-of-band delivery methods since they rely to different protocols and be linked to a specific application. The following packet definition SHOULD be used in out-of-band delivery and MUST be used when Configuration is inlined in the SDP.
</t>
-<figure anchor="Example Fragmented Packet (Packet 2)" title="Example Fragmented Packet (Packet 2)">
-<artwork><![CDATA[
- Packet 2:
+<section anchor="Packed Headers" title="Packed Headers">
- 0 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+<t>
+As mentioned above the RECOMMENDED delivery vector for Vorbis configuration data is via a retrieval method that can be performed using a reliable transport protocol. As the RTP headers are not required for this method of delivery the structure of the configuration data is slightly different. The packed header starts with a 32 bit count field which details the number of packed headers that are contained in the bundle. Next is the Packed header payload for each chained Vorbis stream.
+</t>
+
+<figure anchor="Packed Headers Overview Figure" title="Packed Headers Overview">
+<artwork><![CDATA[
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |V=2|P|X| CC |M| PT | 1001 |
+ | Number of packed headers |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
+ | Packed header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
+ | Packed header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |1|0| 0 | 0| length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
<t>
-The C bit is set to 1 and the number of packets field is set to 0. For large Vorbis fragments there can be several of these type
-of payload packets. The maximum packet size SHOULD be no greater than the path MTU, including all RTP and payload headers. The
-sequence number has been incremented by one but the timestamp field remains the same as the initial packet.
+Since the Configuration Ident and the Identification Header are fixed length there is only a 2 byte length tag to define the length of the packed headers.
</t>
-<figure anchor="Example Fragmented Packet (Packet 3)" title="Example Fragmented Packet (Packet 3)">
+<figure anchor="Packed Headers Detail Figure" title="Packed Headers Detail">
<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 |
+ | Ident | ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
+ .. length | Identification Header ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
+ .. Identification Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Setup Header ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
+ .. Setup Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |1|1| 0 | 0| length | vorbis data ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. vorbis data |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
-
<t>
-This is the last Vorbis fragment packet. The C and F bits are set and the packet count remains set to 0. As in the previous
-packets the timestamp remains set to the first packet in the sequence and the sequence number has been incremented.
+The key difference between the in-band format and this one, is there is no need for the payload header octet.
</t>
-</section>
-<section anchor="Packet Loss" title="Packet Loss">
+<section anchor="Packed Headers IANA Considerations" title="Packed Headers IANA Considerations">
<t>
-As there is no error correction within the Vorbis stream, packet loss will result in a loss of signal. Packet loss is more of an
-issue for fragmented Vorbis packets as the client will have to cope with the handling of the C and F flags. If we use the
-fragmented Vorbis packet example above and the first packet is lost the client SHOULD detect that the next packet has the packet
-count field set to 0 and the C bit is set and MUST drop it. The next packet, which is the final fragmented packet, SHOULD
-be dropped in the same manner, or buffered. Feedback reports on lost and dropped packets MUST be sent back via RTCP.
+The following IANA considerations MUST only be applied to the packed headers.
</t>
<t>
-If a particular multicast session has a large number of participants care must be taken to prevent an RTCP feedback implosion,
-<xref target="rtcp-feedback"></xref>, in the event of packet loss from a large number of participants.
+MIME media type name: audio
</t>
-
<t>
-Loss of any of the configuration headers, detailed below, is dealt with in the Loss of Configuration Headers Section later.
+MIME subtype: vorbis-config
</t>
-</section>
-</section>
-
-<section anchor="Configuration Headers" title="Configuration Headers">
-
<t>
-Unlike other mainstream audio codecs Vorbis has no statically configured probability model, instead it packs all entropy decoding
-configuration, VQ and Huffman models into a self-contained codebook. This codebook block also requires additional identification
-information detailing the number of audio channels, bitrates and other information used to initialise the Vorbis stream.
+Required Parameters:</t><t>
+None.
</t>
<t>
-To decode a Vorbis stream three configuration header blocks are needed. The first header indicates the sample and bitrates, the
-number of channels and the version of the Vorbis encoder used. The second header contains the decoders probability model, or
-codebook and the third header details stream metadata.
+Optional Parameters: </t><t>
+None.
</t>
<t>
-As the RTP stream may change certain configuration data mid-session there are two different methods for delivering this
-configuration data to a client, in-band and SDP which is detailed below. SDP delivery is used to set-up an initial
-state for the client application and in-band is used to change state during the session. The changes may be due to
-different metadata or codebooks as well as different bitrates of the stream.
+Encoding considerations:</t><t>
+This type is only defined for transfer via non RTP protocols as specified in RFC XXXX.
</t>
<t>
-Out of the two delivery vectors the use of an SDP attribute to indicate an URI where the configuration and codebook data
-can be obtained is preferred as they can be fetched reliably using TCP. The in-band codebook delivery SHOULD
-only be used in situations where the link between the client is unidirectional or if the SDP-based information is not available.
+Security Considerations:</t><t>
+See Section 6 of RFC 3047.
</t>
<t>
-Synchronizing the configuration and codebook headers to the RTP stream is critical. The 32 bit Codebook Ident field is used
-to indicate when a change in the stream has taken place. The client application MUST have in advance the correct configuration
-and codebook headers and if the client detects a change in the Ident value and does not have this information it MUST NOT
-decode the raw Vorbis data.
+Interoperability considerations: none
</t>
-<section anchor="In-band Header Transmission" title="In-band Header Transmission">
+<t>
+Published specification:</t>
+<t>See RFC XXXX for details.</t>
<t>
-The three header data blocks are sent in-band with the packet type bits set to match the payload type. Normally the codebook
-and configuration headers are sent once per session if the stream is an encoding of live audio, as typically
-the encoder state will not change, but the encoder state can change at the boundary of chained Vorbis audio files. Metadata
-can be sent at the start as well as any time during the life of the session. Clients MUST be capable of dealing with periodic
-re-transmission of the configuration headers.
+Applications which use this media type:</t><t>
+Vorbis encoded audio, configuration data.
</t>
-<section anchor="Setup Header" title="Setup Header">
+<t>
+Additional information: none
+</t>
<t>
-A Vorbis Setup header is indicated with the payload type field set to 1.
-The Vorbis version MUST be set to zero to comply with this document. The fields Sample Rate, Bitrate Maximum/Nominal/Minimum
-and Num Audio Channels are set in accordance with <xref target="vorbis-spec-ref"></xref> with the bsz fields above referring
-to the blocksize parameters. The framing bit is not used for RTP transportation and so applications constructing Vorbis files
-MUST take care to set this if required.
+Person & email address to contact for further information:</t><t>
+Luca Barbato: <lu_zero at gentoo.org>
</t>
-<figure anchor="Setup Header Figure" title="Setup 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 | xxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | xxxxx |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | synchronization source (SSRC) identifier |
- +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
- | contributing source (CSRC) identifiers |
- | ... |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|1| 2 | 1| bsz 0 | bsz 1 | Num Audio Channels |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Vorbis Version |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Audio Sample Rate |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Bitrate Maximum |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Bitrate Nominal |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Bitrate Minimum |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
+<t>
+Intended usage: COMMON
+</t>
+<t>Author/Change controller:</t>
+<t>Author: Luca Barbato</t>
+<t>Change controller: IETF AVT Working Group</t>
+
+
</section>
+</section>
+</section>
-<section anchor="Codebook Header" title="Codebook Header">
+<section anchor="Loss of Configuration Headers" title="Loss of Configuration Headers">
<t>
-If the payload type field is set to 2, this indicates the packet contains Codebook data.
+Unlike the loss of raw Vorbis payload data, loss of a configuration header can lead to a situation where it will not be possible to successfully decode the stream.
</t>
<t>
-The configuration information detailed below MUST be completely intact, as a client can not decode a stream with an
-incomplete or corrupted codebook set.
+Loss of Configuration Packet results in the halting of stream decoding and SHOULD be reported to the client as well as a loss report sent via RTCP.
</t>
+</section>
+
+<!-- <section anchor="Mapping between Configuration and Stream" title="Mapping between Configuration and Stream">
+
<t>
-A 16 bit codebook length field precedes the codebook datablock. The length field allows for codebooks to be up to 64K
-in size. Packet fragmentation, as per the Vorbis data, MUST be performed if the codebooks size exceeds path MTU. The
-Codebook Ident field MUST be set to match the associated codebook needed to decode the Vorbis stream.
+The mapping between the stream and the the configuration is explicit.
</t>
+</section> -->
+
+
+</section>
+
+<section anchor="Comment Headers" title="Comment Headers">
+
<t>
-The Codebook Ident is the CRC32 checksum of the codebook and is used to detect a corrupted codebook as well as associating
-it with its Vorbis data stream. This Ident value MUST NOT be set to the value of the current stream if this header is being
-sent before the boundary of the chained file has been reached. If a checksum failure is detected then this is considered to
-be a failure and MUST be reported to the client application.
+With the payload type flag set to 2, this indicates that the packet contain the comment metadata, such as artist name, track title and so on. These metadata messages are not intended to be fully descriptive but to offer basic track/song information. Clients MAY ignore it completely. The details on the format of the comments can be found in the <xref target="vorbis-spec-ref">Vorbis documentation</xref>.
</t>
-
-<figure anchor="Codebook Header Figure" title="Codebook Header">
+<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
@@ -608,80 +581,48 @@
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
+ | Ident | 0 | 2 | 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|1| 2 | 1| Codebook Length |
+ | length | Comment ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | Codebook ..
+ .. Comment ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Codebook |
+ .. Comment |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
+<t>The 2 bytes length field is necessary since this packet could be fragmented.</t>
-<section anchor="Codebook CRC32 Generation" title="Codebook CRC32 Generation">
+</section>
+<section anchor="Frame Packetizing" title="Frame Packetizing">
<t>
-In order for different implementations of Vorbis RTP clients and servers to interoperate with each other a common format
-for the production of the CRC32 hash is required. The polynomial is X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0.
+Each RTP packet contains either one Vorbis packet fragment, or an integer number of complete Vorbis packets (up to a max of 15 packets, since the number of packets is defined by a 4 bit value).
</t>
<t>
-The following C code function SHOULD be used by implementations, if not then the code responsible for generating the CRC32
-value MUST use the polynomial function above.
+Any Vorbis data packet that is less than path MTU SHOULD be bundled in the RTP packet with as many Vorbis packets as will fit, up to a maximum of 15. Path MTU is detailed in <xref target="rfc1063"></xref> and <xref target="rfc1981"></xref>.
</t>
-<artwork><![CDATA[
-unsigned int crc32 (int length, unsigned char *crcdata)
-{
- int index, loop;
- unsigned int byte, crc, mask;
-
- index = 0;
- crc = 0xFFFFFFFF;
-
- while (index < length) {
- byte = crcdata [index];
- crc = crc ^ byte;
-
- for (loop = 7; loop >= 0; loop--) {
- mask = -(crc & 1);
- crc = (crc >> 1) ^ (0xEDB88320 & mask);
- }
- index++;
- }
- return ~crc;
-}
-]]></artwork>
-
-
-</section>
-</section>
-
-<section anchor="Metadata Header" title="Metadata Header">
-
<t>
-With the payload type flag set to 3, this indicates that the packet contain the comment metadata, such as artist name, track title
-and so on. These metadata messages are not intended to be fully descriptive but to offer basic track/song information. This
-message MUST be sent at the start of the stream, together with the setup and codebook headers, even if it contains no information.
-During a session the metadata associated with the stream may change from that specified at the start, e.g. a live concert
-broadcast changing acts/scenes, so clients MUST have the ability to receive Metadata header blocks. Details on the format of the
-comments can be found in the Vorbis documentation <xref target="v-comment"></xref>.
+If a Vorbis packet, not only data but also Configuration and Comment, is larger than 65535 octets it MUST be fragmented. A fragmented packet has a zero in the last four bits of the payload header. The first fragment will set the Fragment type to 1. Each fragment after the first will set the Fragment type to 2 in the payload header. The RTP packet containing the last fragment of the Vorbis packet will have the Fragment type set to 3. To maintain the correct sequence for fragmented packet reception the timestamp field of fragmented packets MUST be the same as the first packet sent, with the sequence number incremented as normal for the subsequent RTP packets. The length field shows the fragment length.
</t>
+<section anchor="Example Fragmented Vorbis Packet" title="Example Fragmented Vorbis Packet">
+
<t>
-The format for the data takes the form of a 32 bit codec vendors name length field followed by the name encoded in UTF-8. The
-next 32 bit field denotes the number of user comments. Each of the user comments is prefixed by a 32 bit length field followed by
-the comment text.
+Here is an example fragmented Vorbis packet split over three RTP packets. Each packet contains the standard RTP headers as well as the 4 octet Vorbis headers.
</t>
-<figure anchor="Metadata Header Figure" title="Metadata Header">
+<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 | xxxx |
+ |V=2|P|X| CC |M| PT | 1000 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| xxxxx |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
@@ -691,242 +632,96 @@
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
+ | Ident | 1 | 0 | 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|1| 3 | 1| Vendor string length |
+ | length | vorbis data ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | length | Vendor string ..
+ .. vorbis data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | User comments list length |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | User comment length |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | User comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. User comment |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
-</section>
-</section>
-
-<section anchor="Packed Headers Delivery" title="Packed Headers Delivery">
-
<t>
-As mentioned above the RECOMMENDED delivery vector for Vorbis configuration data is via an SDP attribute as this retrieval method
-can be performed using a reliable transport protocol.
+In this packet the initial sequence number is 1000 and the timestamp is xxxxx. The Fragment type is set to 1, the number of packets field is set to 0, and as the payload is raw Vorbis data the VDT field is set to 0.
</t>
-<figure anchor="Packed Headers Overview Figure" title="Packed Headers Overview">
+<figure anchor="Example Fragmented Packet (Packet 2)" title="Example Fragmented Packet (Packet 2)">
<artwork><![CDATA[
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Number of packed headers |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Packed header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Packed header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
+ Packet 2:
-<t>
-As the RTP headers are not required for this method of delivery the
-structure of the configuration data is slightly different. The packed header starts with a 32 bit count field which details the number of packed headers that are contained in the bundle. Next is the packed header payload for each chained Vorbis file.
-</t>
-
-<figure anchor="Packed Headers Detail Figure" title="Packed Headers Detail">
-<artwork><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Header Length |
+ |V=2|P|X| CC |M| PT | 1001 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Ident |
+ | xxxxx |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Setup Header ..
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Setup Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Header ..
+ | Ident | 2 | 0 | 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Codebook Header |
+ | length | vorbis data ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Metadata Header ..
+ .. vorbis data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Metadata Header |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
-<t>The key difference between the in-band format is there is no need for the payload header octet and Codebook Ident field.
-Below are examples of the packed headers format.
-</t>
-
-<figure anchor="Packed Setup Header Figure" title="Packed Setup 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
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- |0|1| 2 | 1| bsz 0 | bsz 1 | Num Audio Channels |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Vorbis Version |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Audio Sample Rate |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Bitrate Maximum |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Bitrate Nominal |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Bitrate Minimum |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
<t>
-The alignment of the packed Setup Header is slightly different from the RTP payload type as the payload header is not used.
+The Fragment type field is set to 2 and the number of packets field is set to 0. For large Vorbis fragments there can be several of these type of payload packets. The maximum packet size SHOULD be no greater than the path MTU, including all RTP and payload headers. The sequence number has been incremented by one but the timestamp field remains the same as the initial packet.
</t>
-<figure anchor="Packed Codebook Header Figure" title="Packed Codebook Header">
+<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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook Length |
+ |V=2|P|X| CC |M| PT | 1002 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Codebook ..
+ | xxxxx |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- .. Codebook |
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-]]></artwork>
-</figure>
-
-<t>
-The packed Codebook header also has a slightly different structure to that of the RTP payload type. The Codebook Ident field that
-is normally part of this structure is moved to the second field of the overall packed structure.
-</t>
-
-<figure anchor="Packed Metadata Header Figure" title="Packed Metadata 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Vendor string length |
+ | Ident | 3 | 0 | 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | Vendor string |
+ | length | vorbis data ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | User comments list length |
+ .. vorbis data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | User comment length / User comment ..
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
<t>
-The packed Metadata header also as a slightly different structure to that of the RTP payload type with the payload header not being used.
-
+This is the last Vorbis fragment packet. The Fragment type is set to 3 and the packet count remains set to 0. As in the previous packets the timestamp remains set to the first packet in the sequence and the sequence number has been incremented.
</t>
+</section>
-<section anchor="Packed Headers IANA Considerations" title="Packed Headers IANA Considerations">
+<section anchor="Packet Loss" title="Packet Loss">
<t>
-The following IANA considerations MUST only be applied to the packed headers.
+As there is no error correction within the Vorbis stream, packet loss will result in a loss of signal. Packet loss is more of an issue for fragmented Vorbis packets as the client will have to cope with the handling of the Fragment Type. In case of loss of fragments the client MUST discard all the remaining fragments and decode the incomplete packet. If we use the fragmented Vorbis packet example above and the first packet is lost the client MUST detect that the next packet has the packet count field set to 0 and the Fragment type 2 and MUST drop it. The next packet, which is the final fragmented packet, MUST be dropped in the same manner. If the missing packet is the last, the received two fragments will be kept and the incomplete vorbis packet decoded. Feedback reports on lost and dropped packets MUST be sent back via RTCP.
</t>
<t>
-MIME media type name: audio
+If a particular multicast session has a large number of participants care must be taken to prevent an RTCP feedback implosion, <xref target="rtcp-feedback"></xref>, in the event of packet loss from a large number of participants.
</t>
-<t>
-MIME subtype: vorbis-config
-</t>
<t>
-Required Parameters:</t><t>
-None.
+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>
-<t>
-Optional Parameters: </t><t>
-None.
-</t>
-
-<t>
-Encoding considerations:</t><t>
-This type is only defined for transfer via HTTP as specified in RFC XXXX.
-</t>
-
-<t>
-Security Considerations:</t><t>
-See Section 6 of RFC 3047.
-</t>
-
-<t>
-Interoperability considerations: none
-</t>
-
-<t>
-Published specification:</t>
-<t>See RFC XXXX for details.</t>
-
-<t>
-Applications which use this media type:</t><t>
-Vorbis encoded audio, configuration data.
-</t>
-
-<t>
-Additional information: none
-</t>
-
-<t>
-Person & email address to contact for further information:</t><t>
-Phil Kerr: <phil at plus24.com>
-</t>
-
-<t>
-Intended usage: COMMON
-</t>
-
-<t>Author/Change controller:</t>
-<t>Author: Phil Kerr</t>
-<t>Change controller: IETF AVT Working Group</t>
-
-
</section>
</section>
-
-
-
-<section anchor="Codebook Caching" title="Codebook Caching">
-
-<t>
-Codebook caching allows clients that have previously connected to a stream to re-use the associated codebooks and configuration
-data. When a client receives a codebook it may store it locally and can compare the CRC32 key with that of the new stream and
-begin decoding before it has received any of the headers.
-</t>
-
-</section>
-
-<section anchor="Loss of Configuration Headers" title="Loss of Configuration Headers">
-
-<t>
-Unlike the loss of raw Vorbis payload data, loss of a configuration header can lead to a situation where it will not be possible
-to successfully decode the stream.
-</t>
-
-<t>
-Out of the three headers, loss of either the Codebook or Setup headers MUST result in the halting of stream decoding.
-Loss of the Metadata header SHOULD NOT be regarded as fatal for decoding. Loss of any of the headers SHOULD be reported to the
-client as well as a loss report sent via RTCP.
-</t>
-
-
-
-</section>
-</section>
-
<section anchor="IANA Considerations" title="IANA Considerations">
<t>
@@ -937,13 +732,18 @@
</t>
<t>
-Required Parameters:</t><t>
-header indicates the URI of the decoding configuration headers.
+Required Parameters:
</t>
<t>
+delivery-method: indicates the delivery methods in use, the possible values are:inline, in_band, out_band
+</t><t>
+configuration: the <xref target="rfc3548">base16</xref> (hexadecimal) representation of the <xref target="Packed Headers">Packed Headers</xref>.
+</t>
+
+<t>
Optional Parameters: </t><t>
-None.
+configuration-uri: the URI of the configuration headers in case of out of band transmission. In the form of "protocol://path/to/resource/". Depending on the specific method the single ident packet could be retrived by their number, or aggregated in a single stream.
</t>
<t>
@@ -976,7 +776,7 @@
<t>
Person & email address to contact for further information:</t><t>
-Phil Kerr: <phil at plus24.com>
+Luca Barbato: <lu_zero at gentoo.org>
</t>
<t>
@@ -984,15 +784,13 @@
</t>
<t>Author/Change controller:</t>
-<t>Author: Phil Kerr</t>
+<t>Author: Luca Barbato</t>
<t>Change controller: IETF AVT Working Group</t>
<section anchor="Mapping MIME Parameters into SDP" title="Mapping MIME Parameters into SDP">
<t>
-The information carried in the MIME media type specification has a specific mapping to fields in the Session Description
-Protocol (SDP) <xref target="rfc2327"></xref>, which is commonly used to describe RTP sessions. When SDP is used to specify
-sessions the mapping are as follows:
+The information carried in the MIME media type specification has a specific mapping to fields in the Session Description Protocol (SDP) <xref target="rfc2327"></xref>, which is commonly used to describe RTP sessions. When SDP is used to specify sessions the mapping are as follows:
</t>
<vspace blankLines="1" />
@@ -1001,7 +799,7 @@
<t>The MIME type ("audio") goes in SDP "m=" as the media name.</t>
<vspace blankLines="1" />
-<t>The MIME subtype ("VORBIS") goes in SDP "a=rtpmap" as the encoding name.</t>
+<t>The MIME subtype ("vorbis") goes in SDP "a=rtpmap" as the encoding name.</t>
<vspace blankLines="1" />
<t>The parameter "rate" also goes in "a=rtpmap" as clock rate.</t>
@@ -1010,23 +808,27 @@
<t>The parameter "channels" also goes in "a=rtpmap" as channel count.</t>
<vspace blankLines="1" />
-<t>The parameter "header" goes in the SDP "a=fmpt" attribute.</t>
+<t>The mandated parameters "delivery-method" and "configuration" MUST be included in the SDP "a=fmpt" attribute.</t>
+<vspace blankLines="1" />
+
+<t>The optional parameter "configuration-uri", when present, MUST be included in the SDP "a=fmpt" attribute.</t>
+
</list>
+<t>
+If the stream comprises chained Vorbis files and all of them are known in advance, the Configuration Packet for each file SHOULD be passed to the client using the configuration attribute.
+</t>
<t>
-If the stream comprises chained Vorbis files the configuration and codebook headers for each file SHOULD be packaged together
-and passed to the client using the headers attribute if all the files to be played are known in advance.
+The URI specified in the configuration-uri attribute MUST point to a location where all of the Configuration Packets needed for the life of the session reside.
</t>
<t>
-The Vorbis configuration specified in the header attribute MUST contain all of the configuration data and codebooks needed for
-the life of the session.
+The port value is specified by the server application bound to the address specified in the c attribute. The bitrate value and channels specified in the rtpmap attribute MUST match the Vorbis sample rate value. An example is found below.
</t>
<t>
-The port value is specified by the server application bound to the address specified in the c attribute. The bitrate value
-and channels specified in the rtpmap attribute MUST match the Vorbis sample rate value. An example is found below.
+The answer to any offer, <xref target="rfc3264"></xref>, MUST NOT change the URI specified in the configuration-uri attribute. The Configuration inlined in the configuration parameter MAY change.
</t>
<vspace blankLines="1" />
@@ -1034,20 +836,14 @@
<t>c=IN IP4/6 </t>
<t>m=audio RTP/AVP 98</t>
<t>a=rtpmap:98 VORBIS/44100/2</t>
-<t>a=fmtp:98 header=<URL of configuration header> </t>
+<t>a=delivery:out_band/http</t>
+<t>a=fmtp:98 delivery-method:in_band,out_band/http; configuration=base16string1; configuration-uri=http://path/to/the/resource</t>
</list>
<t>
-Note that the payload format (encoding) names are commonly shown in upper case. MIME subtypes are commonly shown in lower
-case. These names are case-insensitive in both places. Similarly, parameter names are case-insensitive both in MIME types and
-in the default mapping to the SDP a=fmtp attribute. The exception regarding case sensitivity is the configuration header URL
-which MUST be regarded as being case sensitive.
+Note that the payload format (encoding) names are commonly shown in upper case. MIME subtypes are commonly shown in lower case. These names are case-insensitive in both places. Similarly, parameter names are case-insensitive both in MIME types and in the default mapping to the SDP a=fmtp attribute. The exception regarding case sensitivity is the configuration-uri URI which MUST be regarded as being case sensitive.
</t>
-<t>
-The answer to any offer, <xref target="rfc3264"></xref>, MUST NOT change the URL specified in the header attribute.
-</t>
-
</section>
</section>
@@ -1055,18 +851,39 @@
<section anchor="Congestion Control" title="Congestion Control">
<t>
-Vorbis clients SHOULD send regular receiver reports detailing congestion. A mechanism for dynamically downgrading the stream,
-known as bitrate peeling, will allow for a graceful backing off of the stream bitrate. This feature is not available at present
-so an alternative would be to redirect the client to a lower bitrate stream if one is available.
+Vorbis clients SHOULD send regular receiver reports detailing congestion. A mechanism for dynamically downgrading the stream, known as bitrate peeling, will allow for a graceful backing off of the stream bitrate. This feature is not available at present so an alternative would be to redirect the client to a lower bitrate stream if one is available.
</t>
<t>
-If a particular multicast session has a large number of participants care must be taken to prevent an RTCP feedback implosion,
-<xref target="rtcp-feedback"></xref>, in the event of congestion.
+If a particular multicast session has a large number of participants care must be taken to prevent an RTCP feedback implosion, <xref target="rtcp-feedback"></xref>, in the event of congestion.
</t>
</section>
+<section anchor="Examples" title="Examples">
+
+<t>
+The following examples are common usage patterns that MAY be applied in such situations, the main scope of this section is to explain better usage of the transmission vectors.
+</t>
+
+<section anchor="Stream Radio" title="Stream Radio">
+
+<t>That is one of the most common situation: one single server streaming content in multicast, the clients may start a session at random time. The content itself could be a mix of live stream as the dj's speech and stored streams as the music she plays.</t>
+
+<t>In this situation we don't know in advance how many codebooks we will use. The clients can join anytime and users expect to start listening to the content in a short time</t>
+
+<t>On join the client will receive the current Configuration necessary to decode the current stream inlined in the SDP. And can start decoding the current stream.</t>
+
+<t>When the streamed content changes the new Configuration is sent in-band before the actual stream, and the Configuration that has to be sent inline in the SDP updated.</t>
+
+<t>A serverside optimization would be keep an hash list of the Configurations per session to avoid packing them and send the same Configuration with different Ident tags</t>
+<t>A clientside optimization would be keep a tag list of the Configurations per session and don't process configuration packets already known.</t>
+
+<t>Let's assume that the client playout buffer can store at least 7 packets.</t>
+
+</section>
+</section>
+
<section anchor="Security Considerations" title="Security Considerations">
<t>
RTP packets using this payload format are subject to the security considerations discussed in the RTP specification
@@ -1080,14 +897,11 @@
<section anchor="Acknowledgments" title="Acknowledgments">
<t>
-This document is a continuation of draft-moffitt-vorbis-rtp-00.txt. The MIME type section is a continuation of
-draft-short-avt-rtp-vorbis-mime-00.txt
+This document is a continuation of draft-moffitt-vorbis-rtp-00.txt and draft-kerr-avt-vorbis-rtp-04.txt. The MIME type section is a continuation of draft-short-avt-rtp-vorbis-mime-00.txt.
</t>
<t>
-Thanks to the AVT, Ogg Vorbis Communities / Xiph.org including Steve Casner, Aaron Colwell, Ross Finlayson, Fluendo, Ramon Garcia,
-Pascal Hennequin, Ralph Giles, Tor-Einar Jarnbjo, Colin Law, John Lazzaro, Jack Moffitt, Christopher Montgomery,
-Colin Perkins, Barry Short, Mike Smith, Michael Sparks, Magnus Westerlund.
+Thanks to the AVT, Ogg Vorbis Communities / Xiph.org including Steve Casner, Aaron Colwell, Ross Finlayson, Fluendo, Ramon Garcia, Pascal Hennequin, Ralph Giles, Tor-Einar Jarnbjo, Colin Law, John Lazzaro, Jack Moffitt, Christopher Montgomery, Colin Perkins, Barry Short, Mike Smith, Phil Kerr, Michael Sparks, Magnus Westerlund, David Barrett, Silvia Pfeiffer, Politecnico di Torino (LS)³/IMG Group in particular Federico Ridolfo, Francesco Varano, Giampaolo Mancini, Juan Carlos De Martin.
</t>
</section>
@@ -1169,6 +983,14 @@
<seriesInfo name="RFC" value="3264" />
</reference>
+<reference anchor="rfc3548">
+<front>
+<title>The Base16, Base32, and Base64 Data Encodings</title>
+<author initials="S." surname="Josefsson" fullname="Simon Josefsson"></author>
+</front>
+<seriesInfo name="RFC" value="3548" />
+</reference>
+
<reference anchor="rtcp-feedback">
<front>
<title>Extended RTP Profile for RTCP-based Feedback (RTP/AVPF)</title>
@@ -1204,13 +1026,6 @@
</front>
</reference>
-<reference anchor="775itu">
-<front>
-<title>ITU (1992-1994) ITU-R Recommendation BS. 775-1 Multi-channel stereophonic sound system with or without accompanying
-picture. International Telecommunications Union. Available from the ITU website, http://www.itu.int</title>
-</front>
-</reference>
-
</references>
</back>
</rfc>
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