Internet DRAFT - draft-ietf-avt-rtp-mime

draft-ietf-avt-rtp-mime









Internet Engineering Task Force      Audio/Video Transport Working Group
INTERNET-DRAFT                                                 S. Casner
draft-ietf-avt-rtp-mime-06.txt                             Packet Design
                                                              P. Hoschka
                                                           W3C/INRIA/MIT
                                                       November 20, 2001
                                                   Expires: May 20, 2002


             MIME Type Registration of RTP Payload Formats

Status of this Memo

This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.

Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups.  Note that other groups
may also distribute working documents as Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt

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                                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.











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1.  Introduction

The MIME registration procedure described in RFC 2048 [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), RFC XXXX [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, RFC YYYY [3], as MIME
subtypes under the "audio" and "video" MIME types.

[Note to RFC Editor:  This paragraph is to be deleted when this draft is
published as an RFC.  References in this draft to RFC XXXX should be
replaced with the RFC number of the revision of RFC 1889 being drafted
as draft-ietf-avt-rtp-new.  References in this draft to RFC YYYY should
be replaced with the RFC number of the revision of RFC 1890 being
drafted as draft-ietf-avt-profile-new.  References in this draft to RFC
ZZZZ should be replaced with the RFC number assigned to this document.]

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




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     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


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] 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 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.



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     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




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        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] 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 "=" 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



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       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, RFC YYYY [3], are registered as
MIME subtypes.

4.1.  Audio Type Registrations

The following sections register all of the RTP audio payload types
defined in RFC YYYY 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



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          specified.

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This type is only defined for transfer via RTP [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     Applications which use this media type:
          Audio and video streaming and conferencing tools.




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     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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>




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     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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





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     Encoding considerations:
          This type is only defined for transfer via RTP [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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>



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     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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





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     Encoding considerations:
          This type is only defined for transfer via RTP [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY





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     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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




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     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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





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     Required parameters: None

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This type is only defined for transfer via RTP [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     Applications which use this media type:
          Audio and video streaming and conferencing tools.




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     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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 RFC 2586 for
transports other than RTP.  That registration is incorporated here and
augmented with additional information for RTP transport.




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     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
          YYYY) 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.




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          This type is also defined for transfer via RTP [RFC XXXX].

     Security considerations
          Audio data is believed to offer no security risks.
          See Section 5 of RFC ZZZZ.

     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 YYYY 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





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     Optional parameters: ptime, maxptime

     Encoding considerations:
          This type is only defined for transfer via RTP [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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.





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          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 XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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




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     Encoding considerations:
          This type is only defined for transfer via RTP [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     Applications which use this media type:
          Audio and video streaming and conferencing tools.





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     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     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

4.1.21.  Registration of MIME media type audio/RED

     MIME media type name: audio

     MIME subtype name: RED




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     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.  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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC 2198

     Applications which use this media type:
          Audio and video streaming and conferencing tools.



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     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 XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     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



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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 XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     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

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 XXXX].





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     Security considerations: See Section 5 of RFC ZZZZ

     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

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 XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     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




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     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     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

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 XXXX].




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     Security considerations: See Section 5 of RFC ZZZZ

     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

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 XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     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




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     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     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





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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 XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     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

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





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     Encoding considerations:
          This type is only defined for transfer via RTP [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     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

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 XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC 2250

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none





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     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 [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     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

4.2.12.  Registration of MIME media type video/BMPEG

     MIME media type name: video

     MIME subtype name: BMPEG





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     Required parameters: None

     Optional parameters: None

     Encoding considerations:
          This type is only defined for transfer via RTP [RFC XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     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

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 XXXX].

     Security considerations: See Section 5 of RFC ZZZZ

     Interoperability considerations: none

     Published specification: RFC YYYY

     Applications which use this media type:
          Audio and video streaming and conferencing tools.




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     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 XXXX, provides security considerations for
the transport of audio and video data over RTP, including the use of
encryption where confidentiality is required.

6.  References

[1] N. Freed, J. Klensin and J. Postel, "Multipurpose Internet Mail
    Extensions (MIME) Part Four: Registration Procedures", RFC 2048,
    November 1996.

[2] H. Schulzrinne, S. Casner, R. Frederick, and V. Jacobson, "RTP:
    A Transport Protocol for real-time applications," RFC 1889,
    January 1996, updated by draft-ietf-avt-rtp-new (Work in
    Progress).

[3] H. Schulzrinne, S. Casner, "RTP profile for audio and video
    conferences with minimal control", RFC 1890, January 1996, updated
    by draft-ietf-avt-profile-new (Work in Progress).

[4] S. Bradner, "Key words for use in RFCs to Indicate Requirement
    Levels", RFC 2119, March 1997.

[5] M. Handley, V. Jacobson and C. Perkins, "SDP: Session Description
    Protocol", RFC 2327, April 1998, updated by
    draft-ietf-mmusic-sdp-new (Work in Progress).

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



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    (MIME) Part One: Format of Internet Message Bodies", RFC 2045,
    November 1996.

[7] K. Kobayashi, A. Ogawa, S. Casner, and C. Bormann, "RTP Payload
    Format for 12-bit DAT, 20- and 24-bit Linear Sampled Audio",
    draft-ietf-avt-dv-audio (Work in Progress).

7.  Authors' Addresses

   Stephen L. Casner
   Packet Design
   2465 Latham Street
   Mountain View, CA 94040
   Phone: +1 650 943-1843
   Email: casner@acm.org

   Philipp Hoschka
   INRIA
   Route des Lucioles 2004
   06904, Sophia-Antipolis Cedex
   BP 93, France
   Tel:(+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 (2001).  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.




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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."













































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