ietf-822
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New Audio Stuff

1991-11-01 12:55:05
Marshall & I, and others, have converged off-line on a new audio format
description.  This is something Marshall & I are both happy with. 
Comments are invited.

----------cut here----------
                            EDITING INSTRUCTIONS


Replace section 7.7 with the text below:
///////
7.7     The Audio Content-Type

A Content-type of "audio" indicates that the body or body part contains
audio data.  Although there is not yet a consensus on an "ideal" audio
format for use with computers, there is a pressing need for a format
capable of providing interoperable behavior.

The initial subtype of "u-law" is specified to meet this requirement.
In addition, a second subtype, "g.721", is specified to provide a
standardized means of exchanging highly-compressed audio encodings of
voice data.

The BNF for the audio type is as follows:

audio-content-type := "audio" "/" audio-subtype
                        *[ ";" attribute "=" value ]

audio-subtype := "u-law" / "g.721" / x-token


7.1.1   The Audio/u-law subtype

The content of this subtype is audio encoded using 8-bit ISDN u-law.
When this subtype is present, the following parameter are optional:

        attribute       meaning
        ---------       -------
        "samplerate"    the integer-valued number of samples/second

                        default value: "8000"

        attribute       meaning
        ---------       -------
        "channels"      the integer-valued number of interleaved channels

                        default value: "1"


7.1.2   The Audio/g.721 subtype

The content of this subtype is audio 8-bit ISDN u-law compressed using
the CCITT G.721 ADPCM voice data encoding scheme.  When this subtype is
present, the following parameters are optional:

        attribute       meaning
        ---------       -------
        "samplerate"    the integer-valued number of samples/second

                        default value: "8000"

        attribute       meaning
        ---------       -------
        "channels"      the integer-valued number of interleaved channels

                        default value: "1"
///////

Add to Appendix A -- Minimal Conformance with This Memo
///////
6. An implementation need not support the Audio content-type value in
order to be conformant to this memo.  However, if conformance to the
Audio content-type value is claimed, then the implementation must be
able to recognize the Audio/u-law subtype, and to render audio encoded
using these parameter pairings:

        attribute       values
        ----------      ------
        samplerate      8000

        channels        1

No conforming implementation will generate an Audio/u-law body
part that does not obey the above constraints.
///////



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