Review requested: audio/atrac-x media type registration

[Tom Taylor]

Please review the following media type registration. The source document is
http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-atrac-family-13.txt,
which is currently undergoing Working Group Last Call in the AVT Working Group.

Tom Taylor
AVT co-Chair

    The media subtype for the Adaptive TRansform Codec version X
    (ATRAC-X) uses the template defined in RFC 4855 [6].

    Note, any unknown parameter MUST be ignored by the receiver.

    Type name:  audio

    Subtype name:  atrac-x

    Required parameters:
    rate:  Represents the sampling frequency in Hz of the original
    audio data.  Permissible values are 44100 and 48000.

    baseLayer:  Indicates the encoded bit-rate in kbps for the audio
    data to be streamed.  Permissible values are 32, 48, 64, 96, 128,
    160, 192, 256, 320 and 352.

    channelID:  Indicates the number of channels and channel layout
    according to the table1 in Section 7.4.  Note that this layout is
    different from that proposed in RFC 3551 [3].  However, as
    channelID = 0 defines an ambiguous channel layout, the channel
    mapping defined in Section 4.1 of [3] could be used. Permissible
    values are 0, 1, 2, 3, 4, 5, 6, 7.

    Optional parameters:

    ptime:    see RFC4566[2]

    maxptime: see RFC4566[2]
    The value of the parameter MUST be a multiple of 46.4(ms) when rate
    parameter is 44100, and 42.6(ms) when rate parameter is 48000.
    If this parameter is not present, the sender MAY encapsulate a
    maximum of 16 encoded frames into one RTP packet, in streaming
    of ATRAC-X.

    maxRedundantFrames:  The maximum number of redundant frames that
    may be sent during a session in any given packet under the redundant
    framing mechanism detailed in the draft. Allowed values are integers
    in the range 0 to 15, inclusive.  If this parameter is not used, a
    default of 15 MUST be assumed.

    delayMode:  Indicates a desire to use low-delay features, in which
    case the decoder will process received data accordingly based on
    this value. Permissible values are 2 and 4.

    Encoding considerations:  This media type is framed and contains
    binary data.

    Security considerations: See Section 9 of this document.

    Interoperability considerations: none

    Published specification: none

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

    Additional information: none

    Magic number(s): none
    File extension(s): 'atx', 'aa3', and 'omg'
    Macintosh file type code(s): none

    Person & email address to contact for further information:
    Mitsuyuki Hatanaka
    actech at jp.sony.com

    Intended usage: COMMON

    Restrictions on usage:  This media type depends on RTP framing,
    and hence is only defined for transfer via RTP.

    Author/Change controller:
    Mitsuyuki Hatanaka
    actech at jp.sony.com