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RFC3555 - MIME Type Registration of RTP Payload Formats

王朝other·作者佚名  2008-05-31
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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 Formats

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.

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

1. Introduction

The MIME registration procedure described in RFC2048 [1] 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), RFC3550 [2], to identify RTP

payload formats.

This document also registers all the RTP payload formats defined in

the RTP Profile for Audio and Video Conferences, RFC3551 [3], 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/MPV

video/MP2T

video/MP1S

video/MP2P

video/BMPEG

video/nv

MIME subtype audio/L16 has already been registered via RFC2586 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 RFC2119 [4] 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 RFC2048 and uses the registration

template shown in Section 2.8 of RFC2048. 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 RFCmay 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.

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].

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.

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 RFC2045 [6] 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 RFC2045 as

attribute "=" value

where 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],

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.

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 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:5

Note 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, RFC3551 [3], are

registered as MIME subtypes.

4.1. Audio Type Registrations

The following sections register all of the RTP audio payload types

defined in RFC3551 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.

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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.2. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.3. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.4. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.5. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.6. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.7. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.8. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.9. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.10. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.11. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.12. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.13. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.14. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.15. Registration of MIME media type audio/L16

MIME subtype audio/L16 has already been registered via RFC2586 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] 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]; those are

DV.LRLsRs, DV.LRCS, DV.LmixRmixTWoQ1Q2. This parameter MUST

be omitted when the AIFF-C channel order convention (see RFC

3551) is in use.

For RTP, ptime: RECOMMENDED duration of each packet in

milliseconds.

For RTP, maxptime: maximum duration of each packet in

milliseconds.

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 [RFC3550].

Security considerations

Audio data is believed to offer no security risks.

See Section 5 of RFC3555.

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

RFC2586 for non-RTP transports, RFC3551 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 : AIFF

Person 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.

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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.17. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.18. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.19. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.1.20. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2658

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

4.1.21. 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 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=yes

Optional parameters: ptime, maxptime

Encoding considerations:

This type is only defined for transfer via RTP [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2198

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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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

4.2. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2431

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

4.2.2. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2029

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

4.2.3. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2435

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

4.2.4. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2032

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

4.2.5. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2190

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

4.2.6. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2429

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

4.2.7. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2429

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

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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2250

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

4.2.9. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2250

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

4.2.10. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2250

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

4.2.11. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2250

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

4.2.12. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC2343

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

4.2.13. 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 [RFC3550].

Security considerations: See Section 5 of RFC3555

Interoperability considerations: none

Published specification: RFC3551

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, RFC3550, provides security considerations for

the transport of audio and video data over RTP, including the use of

encryption where confidentiality is required.

6. Normative References

[1] Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet Mail

Extensions (MIME) Part Four: Registration Procedures", BCP 13,

RFC2048, November 1996.

[2] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson, "RTP:

A Transport Protocol for Real-Time Applications", RFC3550, July

2003.

[3] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video

Conferences with Minimal Control", RFC3551, July 2003.

[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement

Levels", BCP 14, RFC2119, March 1997.

[5] Handley, M. and V. Jacobson, "SDP: Session Description Protocol",

RFC2327, April 1998.

[6] Freed, N. and N. Borenstein, "Multipurpose Internet Mail

Extensions (MIME) Part One: Format of Internet Message Bodies",

RFC2045, 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", RFC3190, January 2002.

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

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 RFCEditor function is currently provided by the

Internet Society.

 
 
 
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