GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc5215

Network Working Group L. Barbato Request for Comments: 5215 Xiph Category: Standards Track August 2008

            RTP Payload Format for Vorbis Encoded Audio

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Abstract

 This document describes an RTP payload format for transporting Vorbis
 encoded audio.  It details the RTP encapsulation mechanism for raw
 Vorbis data and the delivery mechanisms for the decoder probability
 model (referred to as a codebook), as well as 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 Standards Track [Page 1] RFC 5215 Vorbis RTP Payload Format August 2008

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 . . . . . . . . . . . . . . . . . . . .  8
 3.  Configuration Headers  . . . . . . . . . . . . . . . . . . . .  8
   3.1.  In-band Header Transmission  . . . . . . . . . . . . . . .  9
     3.1.1.  Packed Configuration . . . . . . . . . . . . . . . . . 10
   3.2.  Out of Band Transmission . . . . . . . . . . . . . . . . . 12
     3.2.1.  Packed Headers . . . . . . . . . . . . . . . . . . . . 12
   3.3.  Loss of Configuration Headers  . . . . . . . . . . . . . . 13
 4.  Comment Headers  . . . . . . . . . . . . . . . . . . . . . . . 13
 5.  Frame Packetization  . . . . . . . . . . . . . . . . . . . . . 14
   5.1.  Example Fragmented Vorbis Packet . . . . . . . . . . . . . 15
   5.2.  Packet Loss  . . . . . . . . . . . . . . . . . . . . . . . 17
 6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 18
   6.1.  Packed Headers IANA Considerations . . . . . . . . . . . . 19
 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  . . . . . . . . . . 22
 8.  Congestion Control . . . . . . . . . . . . . . . . . . . . . . 22
 9.  Example  . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
   9.1.  Stream Radio . . . . . . . . . . . . . . . . . . . . . . . 22
 10. Security Considerations  . . . . . . . . . . . . . . . . . . . 23
 11. Copying Conditions . . . . . . . . . . . . . . . . . . . . . . 23
 12. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 23
 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
   13.1. Normative References . . . . . . . . . . . . . . . . . . . 24
   13.2. Informative References . . . . . . . . . . . . . . . . . . 25

Barbato Standards Track [Page 2] RFC 5215 Vorbis RTP Payload Format August 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 bit rates.  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 [RFC3533], 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, [RFC2119] 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-octet payload header, and then the payload
 data.  The payload headers are used to associate the Vorbis data with
 its associated decoding codebooks as well as indicate 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 Standards Track [Page 3] RFC 5215 Vorbis RTP Payload Format August 2008

2.1. RTP Header

 The format of the RTP header is specified in [RFC3550] and shown in
 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 [RFC3550] and [RFC3551] 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 [RFC3550].
 Extension (X): 1 bit
 The Extension bit is used in accordance with [RFC3550].
 CSRC count (CC): 4 bits
 The CSRC count is used in accordance with [RFC3550].
 Marker (M): 1 bit
 Set to zero.  Audio silence suppression is not used.  This conforms
 to Section 4.1 of [VORBIS-SPEC-REF].

Barbato Standards Track [Page 4] RFC 5215 Vorbis RTP Payload Format August 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 that 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
 the packet sequence.  This field is detailed further in [RFC3550].
 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 [RFC3550].

2.2. Payload Header

 The 4 octets following the RTP Header section are the Payload Header.
 This header is split into a number of bit fields 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 a network byte order integer.
 Fragment type (F): 2 bits

Barbato Standards Track [Page 5] RFC 5215 Vorbis RTP Payload Format August 2008

 This field is set according to the following list:
    0 = Not Fragmented
    1 = Start Fragment
    2 = Continuation Fragment
    3 = End Fragment
 Vorbis Data Type (VDT): 2 bits
 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 [LIBVORBIS] 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.

Barbato Standards Track [Page 6] RFC 5215 Vorbis RTP Payload Format August 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |            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, and is followed by the raw Vorbis data padded to the nearest
 byte boundary, as explained by the Vorbis I Specification
 [VORBIS-SPEC-REF].  The length value is stored as a network byte
 order integer.
 For payloads that 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 [RFC3551], where the oldest Vorbis packet
 occurs immediately after the RTP packet header.  Subsequent Vorbis
 packets, if any, MUST follow in temporal order.
 Audio channel mapping is in accordance with the Vorbis I
 Specification [VORBIS-SPEC-REF].

Barbato Standards Track [Page 7] RFC 5215 Vorbis RTP Payload Format August 2008

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                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                  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 bit field 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 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

Barbato Standards Track [Page 8] RFC 5215 Vorbis RTP Payload Format August 2008

 information are often referred to collectively as the "codebooks" for
 a Vorbis stream, and are included as special "header" packets at the
 start of the compressed data.  In addition, the Vorbis I
 specification [VORBIS-SPEC-REF] requires the presence of a comment
 header packet that 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 are detailed below.  In order to
 set up an initial state for the client application, the configuration
 MUST be conveyed via the signalling channel used to set up the
 session.  One example of such signalling is SDP [RFC4566] with the
 Offer/Answer Model [RFC3264].  Changes to the configuration MAY be
 communicated via a re-invite, conveying a new SDP, or sent in-band in
 the RTP channel.  Implementations MUST support an in-band delivery of
 updated codebooks, and SHOULD support out-of-band codebook update
 using a new SDP file.  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 inside the Packed Configuration (Section 3.1.1) in the SDP
 as explained the Mapping Media Type Parameters into SDP
 (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.  If the client
 detects a change in the Ident value and does not have this
 information, it MUST NOT decode the raw associated Vorbis data 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 [RFC4588] the configuration headers.  The RTP timestamp value MUST
 reflect the transmission time of the first data packet for which this
 configuration applies.

Barbato Standards Track [Page 9] RFC 5215 Vorbis RTP Payload Format August 2008

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 [VORBIS-SPEC-REF], 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 stores Xiph codec configurations in a
 generic way: 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), and 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 a flag, and the following 7 bits are used to
 store the value.  The first 7 most significant bits are stored in the
 first byte.  If there are remaining bits, the flag bit is set to 1
 and the subsequent 7 bits 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.  To decode,
 simply iterate over the bytes until the flag bit is 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 as they are present in Ogg
 [VORBIS-SPEC-REF]: 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 Standards Track [Page 10] RFC 5215 Vorbis RTP Payload Format August 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                    | 0 | 1 |      1|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           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 because the packet bears the full Packed configuration.  The
 number of the packet is set to 1.

Barbato Standards Track [Page 11] RFC 5215 Vorbis RTP Payload Format August 2008

3.2. Out of Band Transmission

 The following packet definition MUST be used when Configuration is
 inside 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.  The
 following shows the Packed header payload for each chained Vorbis
 stream.
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Number of packed headers                  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Packed header                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Packed header                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   Figure 6: Packed Headers Overview

Barbato Standards Track [Page 12] RFC 5215 Vorbis RTP Payload Format August 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   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 leads to a situation where it will not be possible to
 successfully decode the stream.  Implementations MAY try to recover
 from an 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 either be reset or end the RTP session.

4. Comment Headers

 Vorbis Data Type flag set to 2 indicates that the packet contains the
 comment metadata, such as artist name, track title, and so on.  These
 metadata messages are not intended to be fully descriptive but rather
 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 I Specification [VORBIS-SPEC-REF].

Barbato Standards Track [Page 13] RFC 5215 Vorbis RTP Payload Format August 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                    | 0 | 2 |      1|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |            length             |            Comment           ..
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ..                           Comment                           ..
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ..                           Comment                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 8: Comment Packet
 The 2-byte 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
 [RFC1191] and [RFC1981].
 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 payload 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

Barbato Standards Track [Page 14] RFC 5215 Vorbis RTP Payload Format August 2008

 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 of a fragmented Vorbis packet split over three RTP
 payloads.  Each of them contains the standard RTP headers as well as
 the 4-octet Vorbis headers.
    Packet 1:
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |V=2|P|X|  CC   |M|     PT      |           1000                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                            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.

Barbato Standards Track [Page 15] RFC 5215 Vorbis RTP Payload Format August 2008

    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
 these types 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.

Barbato Standards Track [Page 16] RFC 5215 Vorbis RTP Payload Format August 2008

    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 two fragments received 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.

Barbato Standards Track [Page 17] RFC 5215 Vorbis RTP Payload Format August 2008

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
       [RFC3551].
    channels:  indicates the number of audio channels as described in
       RTP Profile for Audio and Video Conferences with Minimal
       Control [RFC3551].
    configuration:  the base64 [RFC4648] 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 5215.
 Interoperability considerations:
    None
 Published specification:
    RFC 5215
    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

Barbato Standards Track [Page 18] RFC 5215 Vorbis RTP Payload Format August 2008

 Person & email address to contact for further information:
    Luca Barbato: <lu_zero@gentoo.org>
    IETF Audio/Video Transport Working Group
 Intended usage:
    COMMON
 Restriction on usage:
    This media type depends on RTP framing, hence is only defined for
    transfer via RTP [RFC3550].
 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 5215.
 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 5215.

Barbato Standards Track [Page 19] RFC 5215 Vorbis RTP Payload Format August 2008

 Interoperability considerations:
    None
 Published specification:
    RFC 5215
 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@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 [RFC3264].  In order to be forward compatible, the
 implementation MUST ignore unknown parameters.

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)
 [RFC4566], which is commonly used to describe RTP sessions.  When SDP
 is used to specify sessions, the mapping are as follows:

Barbato Standards Track [Page 20] RFC 5215 Vorbis RTP Payload Format August 2008

 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 the clock rate.
 o  The parameter "channels" also goes in "a=rtpmap" as the 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 channel count value specified
 in the rtpmap attribute SHOULD match the current Vorbis stream or
 should be considered the maximum number of channels to be expected.
 The timestamp clock rate MUST be a multiple of the sample rate; a
 different payload number MUST be used if the clock rate changes.  The
 Configuration payload delivers the exact information, thus the SDP
 information SHOULD be considered 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 inside the SDP; other configurations could be
 fetched at any time from the URIs provided.  The following base64
 [RFC4648] 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
 uppercase.  Media Type subtypes are commonly shown in lowercase.
 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

Barbato Standards Track [Page 21] RFC 5215 Vorbis RTP Payload Format August 2008

 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

 There are no negotiable parameters.  All of them are declarative.

8. Congestion Control

 The general congestion control considerations for transporting RTP
 data apply to Vorbis audio over RTP as well.  See the RTP
 specification [RFC3550] and any applicable RTP profile (e.g.,
 [RFC3551]).  Audio data can be encoded using a range of different bit
 rates, so it is possible to adapt network bandwidth by adjusting the
 encoder bit rate in real time or by having multiple copies of content
 encoded at different bit rates.

9. Example

 The following example shows a common usage pattern that MAY be
 applied in such a 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 situations: there is one single server
 streaming content in multicast, and the clients may start a session
 at a random time.  The content itself could be a mix of a 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.
 Upon joining, the client will receive the current Configuration
 necessary to decode the current stream inside 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 inside the SDP is 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 [RFC3611] if the server
 supports this feature.

Barbato Standards Track [Page 22] RFC 5215 Vorbis RTP Payload Format August 2008

 A server-side optimization would be to keep a hash list of the
 Configurations per session, which avoids packing all of them and
 sending the same Configuration with different Ident tags.
 A client-side optimization would be to keep a tag list of the
 Configurations per session and not process configuration packets that
 are already known.

10. Security Considerations

 RTP packets using this payload format are subject to the security
 considerations discussed in the RTP specification [RFC3550], the
 base64 specification [RFC4648], and the URI Generic syntax
 specification [RFC3986].  Among other considerations, this implies
 that the confidentiality of the media stream is achieved by using
 encryption.  Because the data compression used with this payload
 format is applied end-to-end, encryption may be performed on the
 compressed data.

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 the following documents:
 Moffitt, J., "RTP Payload Format for Vorbis Encoded Audio", February
 2001.
 Kerr, R., "RTP Payload Format for Vorbis Encoded Audio", December
 2004.
 The Media Type declaration is a continuation of the following
 document:
 Short, B., "The audio/rtp-vorbis MIME Type", January 2008.
 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, Gianni Ceccarelli, and

Barbato Standards Track [Page 23] RFC 5215 Vorbis RTP Payload Format August 2008

 Alessandro Salvatori.  Thanks to the LScube Group, in particular
 Federico Ridolfo, Francesco Varano, Giampaolo Mancini, Dario
 Gallucci, and Juan Carlos De Martin.

13. References

13.1. Normative References

 [RFC1191]          Mogul, J. and S. Deering, "Path MTU discovery",
                    RFC 1191, November 1990.
 [RFC1981]          McCann, J., Deering, S., and J. Mogul, "Path MTU
                    Discovery for IP version 6", RFC 1981,
                    August 1996.
 [RFC2119]          Bradner, S., "Key words for use in RFCs to
                    Indicate Requirement Levels", BCP 14, RFC 2119,
                    March 1997.
 [RFC3264]          Rosenberg, J. and H. Schulzrinne, "An Offer/Answer
                    Model with Session Description Protocol (SDP)",
                    RFC 3264, June 2002.
 [RFC3550]          Schulzrinne, H., Casner, S., Frederick, R., and V.
                    Jacobson, "RTP: A Transport Protocol for Real-Time
                    Applications", STD 64, RFC 3550, July 2003.
 [RFC3551]          Schulzrinne, H. and S. Casner, "RTP Profile for
                    Audio and Video Conferences with Minimal Control",
                    STD 65, RFC 3551, July 2003.
 [RFC3986]          Berners-Lee, T., Fielding, R., and L. Masinter,
                    "Uniform Resource Identifier (URI): Generic
                    Syntax", STD 66, RFC 3986, January 2005.
 [RFC4566]          Handley, M., Jacobson, V., and C. Perkins, "SDP:
                    Session Description Protocol", RFC 4566,
                    July 2006.
 [RFC4648]          Josefsson, S., "The Base16, Base32, and Base64
                    Data Encodings", RFC 4648, October 2006.
 [VORBIS-SPEC-REF]  "Ogg Vorbis I specification:  Codec setup and
                    packet decode.  Available from the Xiph website,
                    http://xiph.org/vorbis/doc/Vorbis_I_spec.html".

Barbato Standards Track [Page 24] RFC 5215 Vorbis RTP Payload Format August 2008

13.2. Informative References

 [LIBVORBIS]        "libvorbis: Available from the dedicated website,
                    http://vorbis.com/".
 [RFC3533]          Pfeiffer, S., "The Ogg Encapsulation Format
                    Version 0", RFC 3533, May 2003.
 [RFC3611]          Friedman, T., Caceres, R., and A. Clark, "RTP
                    Control Protocol Extended Reports (RTCP XR)",
                    RFC 3611, November 2003.
 [RFC4588]          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@gentoo.org
 URI:   http://xiph.org/

Barbato Standards Track [Page 25] RFC 5215 Vorbis RTP Payload Format August 2008

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@ietf.org.

Barbato Standards Track [Page 26]

/data/webs/external/dokuwiki/data/pages/rfc/rfc5215.txt · Last modified: 2008/08/11 22:30 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki