MIME Type Registration of RTP Payload Formats (original) (raw)
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Obsoleted by: 4855, 4856 PROPOSED STANDARD
Updated by: 3625, 4629
Network Working Group S. Casner Request for Comments: 3555 Packet Design Category: Standards Track P. Hoschka W3C/INRIA/MIT July 2003
MIME Type Registration of RTP Payload FormatsStatus 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.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document defines the procedure to register RTP Payload Formats as audio, video or other MIME subtype names. This is useful in a text-based format or control protocol to identify the type of an RTP transmission. This document also registers all the RTP payload formats defined in the RTP Profile for Audio and Video Conferences as MIME subtypes. Some of these may also be used for transfer modes other than RTP.
Table of Contents
1. Introduction .................................................. 2 1.1. IANA Considerations ...................................... 2 1.2. Terminology .............................................. 3 2. Procedure For Registering MIME Types for RTP Payload Types .... 3 3. Mapping to SDP Parameters ..................................... 5 4. Registrations for "Audio/Video Profile" ....................... 6 4.1. Audio Type Registrations ................................. 6 4.2. Video Type Registrations ................................. 30 5. Security Considerations ....................................... 42 6. Normative References .......................................... 43 7. Authors' Addresses ............................................ 44 8. Full Copyright Statement ...................................... 45
Casner & Hoschka Standards Track [Page 1]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
1. Introduction
The MIME registration procedure described in RFC 2048 [[1](#ref-1 ""Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures"")] was originally designed for transport of multimedia information via asynchronous Internet mail, but the MIME namespace now provides identification for other transport modes as well. This document defines the procedure to register MIME subtype names for use with the Real-time Transport Protocol (RTP), RFC 3550 [[2](#ref-2 ""RTP: A Transport Protocol for Real-Time Applications"")], to identify RTP payload formats.
This document also registers all the RTP payload formats defined in the RTP Profile for Audio and Video Conferences, RFC 3551 [[3](#ref-3 ""RTP Profile for Audio and Video Conferences with Minimal Control"")], as MIME subtypes under the "audio" and "video" MIME types.
1.1. IANA Considerations
This document registers the following MIME subtypes:
audio/DVI4
audio/G722
audio/G723
audio/G726-16
audio/G726-24
audio/G726-32
audio/G726-40
audio/G728
audio/G729
audio/G729D
audio/G729E
audio/GSM
audio/GSM-EFR
audio/L8
audio/L16
audio/LPC
audio/MPA
audio/PCMA
audio/PCMU
audio/QCELP
audio/RED
audio/VDVI
video/BT656
video/CelB
video/JPEG
video/H261
video/H263
video/H263-1998
video/H263-2000
video/MPVCasner & Hoschka Standards Track [Page 2]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
video/MP2T
video/MP1S
video/MP2P
video/BMPEG
video/nvMIME subtype audio/L16 has already been registered via RFC 2586 for transports other than RTP. That registration is incorporated here and augmented with additional information for RTP transport.
1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [[4](#ref-4 ""Key words for use in RFCs to Indicate Requirement Levels"")] and indicate requirement levels for implementations compliant with this specification.
2. Procedure For Registering MIME Types for RTP Payload Types
Registering an RTP payload type as a MIME type follows the same procedures as described in RFC 2048 and uses the registration template shown in Section 2.8 of RFC 2048. Some additional parameters are required to specify how a particular payload format is transported over RTP:
Published specification
A description of the encoding and a specification of the
payload format must be provided, usually by reference to an RTP
payload format specification RFC. That RFC may be separate, or
the MIME subtype registration may be incorporated into the
payload format specification RFC. The payload format
specification MUST include the RTP timestamp clock rate (or
multiple rates for audio encodings with multiple sampling
rates).
A reference to a further description of the data compression
format itself should be provided, if available.
Required parameters
If the payload format does not have a fixed RTP timestamp clock
rate, then a "rate" parameter is required to specify the RTP
timestamp clock rate. A particular payload format may have
additional required parameters.Casner & Hoschka Standards Track [Page 3]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
Optional parameters
Most audio payload formats can have an optional "channels"
parameter to specify the number of audio channels included in
the transmission. Any payload format, but most likely audio
formats, may also include the optional parameters "ptime", to
specify the recommended length of time in milliseconds
represented by the media in a packet, and/or "maxptime" to
specify the maximum amount of media which can be encapsulated
in each packet, expressed as time in milliseconds. The "ptime"
and "maxptime" parameters are defined in the Session
Description Protocol (SDP) [[5](#ref-5 ""SDP: Session Description Protocol"")].
A particular payload format may have additional optional
parameters.
Encoding considerations
The fact that the type can be transferred via RTP MUST be
noted.Depending on whether the type has already been registered for transfer with a non-RTP protocol (e.g. MIME mail or http) or not, several different cases can occur:
a) Not yet registered as a MIME type
A new registration should be constructed using the MIME
registration template. The registration may specify transfer
via other means in addition to RTP if that is feasible and
desired. The encoding considerations must specify how the type
is transferred via RTP.
Optional parameters may be defined as needed, and it must be
clearly stated whether to which mode(s) of transfer the
parameters apply.
b) MIME type exists for a non-RTP protocol
The encoding considerations of the existing type should be
changed to indicate that the type can also be transferred via
RTP.
RTP-specific parameters may be added, and it must be clearly
stated that these are only to be used when the media type is
transmitted via RTP transport.Casner & Hoschka Standards Track [Page 4]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
c) Update an existing MIME type for RTP to be used for a non-RTP
protocol
The encoding considerations of the existing type should be
changed to indicate that the type can also be transferred via a
non-RTP protocol (e.g. SMTP, HTTP).
Non-RTP-specific parameters can be added, and it must be
clearly stated that these are only to be used when the media
type is transmitted via a non-RTP transport.3. Mapping to SDP Parameters
The representation of a MIME media type is specified in the syntax of the Content-Type header field in RFC 2045 [[6](#ref-6 ""Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies"")] as follows:
type "/" subtype *(";" parameter)Parameters may be required for a particular type or subtype or they may be optional. For media types which represent RTP payload formats, the parameters "rate", "channels", "ptime", and "maxptime" have general definitions (given above) that may apply across types and subtypes. The format for a parameter is specified in RFC 2045 as
attribute "=" valuewhere attribute is the parameter name and the permissible values are specified for each parameter. The value may need to be a quoted string if it contains any of the special characters listed in RFC 2045.
The information carried in the media type string has a specific mapping to fields in the Session Description Protocol (SDP) [[5](#ref-5 ""SDP: Session Description Protocol"")], which is commonly used to describe RTP sessions. The mapping is as follows:
o The MIME type (e.g., audio) goes in SDP "m=" as the media name.
o The MIME subtype (payload format) goes in SDP "a=rtpmap" as the
encoding name.
o The general (possibly optional) parameters "rate" and
"channels" also go in "a=rtpmap" as clock rate and encoding
parameters, respectively.
o The general (and optional) parameters "ptime" and "maxptime" go
in the SDP "a=ptime" and "a=maxptime" attributes, respectively.Casner & Hoschka Standards Track [Page 5]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
o Any payload-format-specific parameters go in the SDP "a=fmtp"
attribute. The set of allowed parameters is defined by the RFC
that specifies the payload format and MUST NOT be extended by
the MIME subtype registration without a corresponding revision
of the payload format specification. The format and syntax of
these parameters may also be defined by the payload format
specification, but it is suggested that the parameters be
copied directly from the MIME media type string as a semicolon
separated list of parameter=value pairs. For payload formats
that specify some other syntax for the fmtp parameters, the
registration of that payload format as a MIME subtype must
specify what the parameters are in MIME format and how to map
them to the SDP "a=fmtp" attribute. See [Section 4.1.21](#section-4.1.21) for an
example.An example mapping is as follows:
audio/L16; rate=48000; channels=2; ptime=5; emphasis=50-15
m=audio 49170 RTP/AVP 97
a=rtpmap:97 L16/48000/2
a=fmtp:97 emphasis=50-15
a=ptime:5Note that the payload format (encoding) names defined in the RTP Profile 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.
4. Registrations for "Audio/Video Profile"
In the following sections, all RTP payload formats described in the RTP Profile for Audio and Video Conferences, RFC 3551 [[3](#ref-3 ""RTP Profile for Audio and Video Conferences with Minimal Control"")], are registered as MIME subtypes.
4.1. Audio Type Registrations
The following sections register all of the RTP audio payload types defined in RFC 3551 as MIME types.
For most audio payload formats, the RTP timestamp clock rate is equal to the sampling rate. Some payload formats operate only at one fixed sampling rate, while others are adjustable.
Casner & Hoschka Standards Track [Page 6]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.1. Registration of MIME media type audio/DVI4
MIME media type name: audio
MIME subtype name: DVI4
Required parameters: rate The RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000, but other rates may be specified.
Optional parameters: ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 7]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.2. Registration of MIME media type audio/G722
MIME media type name: audio
MIME subtype name: G722
Required parameters: None
Optional parameters: ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 8]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.3. Registration of MIME media type audio/G723
MIME media type name: audio
MIME subtype name: G723
Required parameters: None
Optional parameters: ptime, maxptime
bitrate: the data rate in kb/s used or preferred for the audio
bit stream, with permissible values 5.3 or 6.3. If
unspecified, the bitrate may change from frame to frame as
indicated inband.
annexa: indicates that Annex A, voice activity detection, is
used or preferred. Permissible values are "yes" and "no"
(without the quotes); "yes" is implied if this parameter is
omitted.Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 9]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.4. Registration of MIME media type audio/G726-16
MIME media type name: audio
MIME subtype name: G726-16
Required parameters: None
Optional parameters: ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 10]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.5. Registration of MIME media type audio/G726-24
MIME media type name: audio
MIME subtype name: G726-24
Required parameters: None
Optional parameters: ptime, maxptime
Encoding considerations:
This type is only defined for transfer via RTP [[RFC 3550](./rfc3550)].Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 11]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.6. Registration of MIME media type audio/G726-32
MIME media type name: audio
MIME subtype name: G726-32
Required parameters: None
Optional parameters: ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 12]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.7. Registration of MIME media type audio/G726-40
MIME media type name: audio
MIME subtype name: G726-40
Required parameters: None
Optional parameters: ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 13]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.8. Registration of MIME media type audio/G728
MIME media type name: audio
MIME subtype name: G728
Required parameters: None
Optional parameters: ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 14]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.9. Registration of MIME media type audio/G729
MIME media type name: audio
MIME subtype name: G729
Required parameters: None
Optional parameters: ptime, maxptime
annexb: indicates that Annex B, voice activity detection, is
used or preferred. Permissible values are "yes" and "no"
(without the quotes); "yes" is implied if this parameter is
omitted.Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 15]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.10. Registration of MIME media type audio/G729D
MIME media type name: audio
MIME subtype name: G729D
Required parameters: None
Optional parameters: ptime, maxptime
annexb: indicates that Annex B, voice activity detection, is
used or preferred. Permissible values are "yes" and "no"
(without the quotes); "yes" is implied if this parameter is
omitted.Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 16]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.11. Registration of MIME media type audio/G729E
MIME media type name: audio
MIME subtype name: G729E
Required parameters: None
Optional parameters: ptime, maxptime
annexb: indicates that Annex B, voice activity detection, is
used or preferred. Permissible values are "yes" and "no"
(without the quotes); "yes" is implied if this parameter is
omitted.Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 17]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.12. Registration of MIME media type audio/GSM
MIME media type name: audio
MIME subtype name: GSM
Required parameters: None
Optional parameters: ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 18]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.13. Registration of MIME media type audio/GSM-EFR
MIME media type name: audio
MIME subtype name: GSM-EFR
Required parameters: None
Optional parameters: ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 19]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.14. Registration of MIME media type audio/L8
MIME media type name: audio
MIME subtype name: L8
Required parameters: rate, the RTP timestamp clock rate
Optional parameters: channels, ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 20]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.15. Registration of MIME media type audio/L16
MIME subtype audio/L16 has already been registered via RFC 2586 for transports other than RTP. That registration is incorporated here and augmented with additional information for RTP transport.
MIME media type name: audio
MIME subtype name: L16
Required parameters rate: number of samples per second -- For non-RTP transport, the permissible values for rate are 8000, 11025, 16000, 22050, 24000, 32000, 44100, and 48000 samples per second. For RTP transport, other values are permissible but the aforementioned values are RECOMMENDED. For RTP, the rate parameter indicates the RTP timestamp clock rate, which is equal to the sample rate.
Optional parameters channels: how many audio streams are interleaved -- defaults to 1; stereo would be 2, etc. Interleaving takes place between individual two-byte samples.
emphasis: analog preemphasis applied to the signal before
quantization. The only emphasis value defined here is
emphasis=50-15 to indicate the 50/15 microsecond preemphasis
used with Compact Disks. This parameter MUST be omitted if no
analog preemphasis was applied.
channel-order: specifies the sample interleaving order for
multiple-channel audio streams (see [[7](#ref-7 ""RTP Payload Format for 12-bit DAT Audio and 20- and 24-bit Linear Sampled Audio"")] [Section 7](#section-7)).
Permissible values are DV.LRLsRs, DV.LRCS, DV.LRCWo,
DV.LRLsRsC, DV.LRLsRsCS, DV.LmixRmixTWoQ1Q2,
DV.LRCWoLsRsLmixRmix, DV.LRCWoLs1Rs1Ls2Rs2, DV.LRCWoLsRsLcRc.
For interoperation with DV video systems, only a subset of
these channel combinations is specified for use with 20-bit
linear encoding in the DV video specification [[4](#ref-4 ""Key words for use in RFCs to Indicate Requirement Levels"")]; those are
DV.LRLsRs, DV.LRCS, DV.LmixRmixTWoQ1Q2. This parameter MUST
be omitted when the AIFF-C channel order convention (see [RFC](./rfc3551)
[3551](./rfc3551)) is in use.
For RTP, ptime: RECOMMENDED duration of each packet in
milliseconds.
For RTP, maxptime: maximum duration of each packet in
milliseconds.Casner & Hoschka Standards Track [Page 21]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
Encoding considerations Audio data is binary data, and must be encoded for non-binary transport; the Base64 encoding is suitable for Email. Note that audio data does not compress easily using lossless compression.
This type is also defined for transfer via RTP [[RFC 3550](./rfc3550)].Security considerations Audio data is believed to offer no security risks. See Section 5 of RFC 3555.
Interoperability considerations This type is compatible with the encoding used in the WAV (Microsoft Windows RIFF) and Apple AIFF union types, and with the public domain "sox" and "rateconv" programs.
Published specification RFC 2586 for non-RTP transports, RFC 3551 for RTP
Applications which use this media The public domain "sox" and "rateconv" programs accept this type.
1. Magic number(s) : None
2. File extension(s) : WAV L16
3. Macintosh file type code : AIFFPerson to contact for further information 1. Name : James Salsman 2. E-mail : jps-L16@bovik.org
Intended usage Common
It is expected that many audio and speech applications will
use this type. Already the most popular platforms provide
this type with the rate=11025 parameter referred to as "radio
quality speech."Author/Change controller James Salsman for non-RTP transports. Stephen Casner for RTP transport.
Casner & Hoschka Standards Track [Page 22]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.16. Registration of MIME media type audio/LPC
MIME media type name: audio
MIME subtype name: LPC
Required parameters: None
Optional parameters: ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 23]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.17. Registration of MIME media type audio/MPA
MIME media type name: audio
MIME subtype name: MPA (MPEG audio)
Required parameters: None
Optional parameters: layer: which layer of MPEG audio encoding; permissible values are 1, 2, 3.
samplerate: the rate at which audio is sampled. MPEG-1 audio
supports sampling rates of 32, 44.1, and 48 kHz; MPEG-2
supports sampling rates of 16, 22.05 and 24 kHz. This parameter
is separate from the RTP timestamp clock rate which is always
90000 Hz for MPA.
mode: permissible values are "stereo", "joint_stereo",
"single_channel", "dual_channel". The "channels" parameter
does not apply to MPA. It is undefined to put a number of
channels in the SDP rtpmap attribute for MPA.
bitrate: the data rate for the audio bit stream.
ptime: RECOMMENDED duration of each packet in milliseconds.
maxptime: maximum duration of each packet in milliseconds.
Parameters which are omitted are left to the encoder to choose
based on the session bandwidth, configuration information, or
other constraints. The selected layer as well as the sampling
rate and mode are indicated in the payload so receivers can
process the data without these parameters being specified
externally.Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Casner & Hoschka Standards Track [Page 24]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
4.1.18. Registration of MIME media type audio/PCMA
MIME media type name: audio
MIME subtype name: PCMA
Required parameters: rate The RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000, but other rates may be specified.
Optional parameters: channels, ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 25]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.19. Registration of MIME media type audio/PCMU
MIME media type name: audio
MIME subtype name: PCMU
Required parameters: rate The RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000, but other rates may be specified.
Optional parameters: channels, ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 26]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.20. Registration of MIME media type audio/QCELP
MIME media type name: audio
MIME subtype name: QCELP
Required parameters: None
Optional parameters: ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2658
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 27]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.1.21. Registration of MIME media type audio/RED
MIME media type name: audio
MIME subtype name: RED
Required parameters: pt: a comma-separated list of RTP payload types. Because comma is a special character, the list must be a quoted-string (enclosed in double quotes). For static payload types, each list element is simply the type number. For dynamic payload types, each list element is a mapping of the dynamic payload type number to an embedded MIME content-type specification for the payload format corresponding to the dynamic payload type. The format of the mapping is:
dynamic-payload-type "=" content-type
If the content-type string includes a comma, then the
content-type string MUST be a quoted-string. If the content-
type string does not include a comma, it MAY still be quoted.
Since it is part of the list which must itself be a quoted-
string, that means the quotation marks MUST be quoted with
backslash quoting as specified in [RFC 2045](./rfc2045). If the content-
type string itself contains a quoted-string, then the
requirement for backslash quoting is recursively applied. To
specify the audio/RED payload format in SDP, the pt parameter
is mapped to an a=fmtp attribute by eliminating the parameter
name (pt) and changing the commas to slashes. For example,
'pt="0,5"' maps to 'a=fmtp:99 0/5'. A more complicated
example, with a dynamic payload type, is:
pt = "0, 103 = \"audio/G729D;annexb=yes\" "
m=audio 49170 RTP/AVP 99 0 103
a=rtpmap:99 RED/8000
a=fmtp:99 0/103
a=rtpmap:103 G729D/8000
a=fmtp:103 annexb=yesOptional parameters: ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Casner & Hoschka Standards Track [Page 28]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
Published specification: RFC 2198
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
4.1.22. Registration of MIME media type audio/VDVI
MIME media type name: audio
MIME subtype name: VDVI
Required parameters: None
Optional parameters: ptime, maxptime
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 29]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2. Video Type Registrations
For all of the video payload formats registered here, the RTP timestamp clock rate is always 90000 Hz, so the "rate" parameter is not applicable. Likewise, the "channel" parameter is not used with video, and while "ptime" and "maxptime" could be used with video, they typically are not.
4.2.1. Registration of MIME media type video/BT656
MIME media type name: video
MIME subtype name: BT656
Required parameters: None
Optional parameters: None
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2431
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 30]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2.2. Registration of MIME media type video/CelB
MIME media type name: video
MIME subtype name: CelB
Required parameters: None
Optional parameters: None
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2029
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 31]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2.3. Registration of MIME media type video/JPEG
MIME media type name: video
MIME subtype name: JPEG
Required parameters: None
Optional parameters: None
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2435
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 32]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2.4. Registration of MIME media type video/H261
MIME media type name: video
MIME subtype name: H261
Required parameters: None
Optional parameters: None
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2032
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 33]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2.5. Registration of MIME media type video/H263
MIME media type name: video
MIME subtype name: H263
Required parameters: None
Optional parameters: None
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2190
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 34]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2.6. Registration of MIME media type video/H263-1998
MIME media type name: video
MIME subtype name: H263-1998
Required parameters: None
Optional parameters: None
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2429
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 35]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2.7. Registration of MIME media type video/H263-2000
MIME media type name: video
MIME subtype name: H263-2000
Required parameters: None
Optional parameters: profile: H.263 profile number, in the range 0 through 10, specifying the supported H.263 annexes/subparts.
level: Level of bitstream operation, in the range 0 through
100, specifying the level of computational complexity of the
decoding process.Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2429 The specific values for the profile and level parameters and their meaning are defined in Annex X of ITU-T Recommendation H.263, "Video coding for low bit rate communication". Note that the RTP payload format for H263-2000 is the same as for H263-1998, but additional annexes/subparts are specified along with the profiles and levels.
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 36]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2.8. Registration of MIME media type video/MPV
MIME media type name: video
MIME subtype name: MPV MPEG-1 or -2 Elementary Streams
Required parameters: None
Optional parameters: type: the type of MPEG video, from the set "mpeg1", "mpeg2-halfd1", or "mpeg2-fulld1". The default is "mpeg1". The mapping to a=fmtp is identity.
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2250
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 37]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2.9. Registration of MIME media type video/MP2T
MIME media type name: video
MIME subtype name: MP2T MPEG-2 Transport Streams
Required parameters: None
Optional parameters: None
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2250
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 38]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2.10. Registration of MIME media type video/MP1S
MIME media type name: video
MIME subtype name: MP1S MPEG-1 Systems Streams
Required parameters: None
Optional parameters: None
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2250
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 39]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2.11. Registration of MIME media type video/MP2P
MIME media type name: video
MIME subtype name: MP2P MPEG-2 Program Streams
Required parameters: None
Optional parameters: None
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2250
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 40]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2.12. Registration of MIME media type video/BMPEG
MIME media type name: video
MIME subtype name: BMPEG
Required parameters: None
Optional parameters: None
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 2343
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
Casner & Hoschka Standards Track [Page 41]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
4.2.13. Registration of MIME media type video/nv
MIME media type name: video
MIME subtype name: nv
Required parameters: None
Optional parameters: None
Encoding considerations: This type is only defined for transfer via RTP [RFC 3550].
Security considerations: See Section 5 of RFC 3555
Interoperability considerations: none
Published specification: RFC 3551
Applications which use this media type: Audio and video streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information: Stephen Casner casner@acm.org
Intended usage: COMMON
Author/Change controller: Stephen Casner
5. Security Considerations
The MIME subtype registration procedure specified in this memo does not impose any security considerations on its own. This memo also contains several MIME type registrations. The registrations themselves do not impose security risks, but some may state security considerations specific to the particular registration.
Several audio and video encodings are perfect for hiding data using steganography.
The RTP specification, RFC 3550, provides security considerations for the transport of audio and video data over RTP, including the use of encryption where confidentiality is required.
Casner & Hoschka Standards Track [Page 42]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
6. Normative References
[1] Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", BCP 13, RFC 2048, November 1996.
[2] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", RFC 3550, July 2003.
[3] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video Conferences with Minimal Control", RFC 3551, July 2003.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[5] Handley, M. and V. Jacobson, "SDP: Session Description Protocol", RFC 2327, April 1998.
[6] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996.
[7] Kobayashi, K., Ogawa, A., Casner, S. and C. Bormann, "RTP Payload Format for 12-bit DAT Audio and 20- and 24-bit Linear Sampled Audio", RFC 3190, January 2002.
Casner & Hoschka Standards Track [Page 43]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
7. Authors' Addresses
Stephen L. Casner Packet Design 3400 Hillview Avenue, Building 3 Palo Alto, CA 94304 United States
Phone: +1 650 739-1843 EMail: casner@acm.org
Philipp Hoschka INRIA Route des Lucioles 2004 06904, Sophia-Antipolis Cedex BP 93, France
Phone: (+33) 4 92 38 79 84 Fax: (+33) 4 92 38 77 65 EMail: ph@w3.org
W3C http://www.w3.org/people/hoschka
Casner & Hoschka Standards Track [Page 44]
RFC 3555 MIME Type Registration of RTP Payload Formats July 2003
8. Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the Internet Society.
Casner & Hoschka Standards Track [Page 45]