[AVT] Media types registration (was: AVT meeting in Paris (IETF 63): Agenda Requests)

[Stephen Casner <casner at acm.org>]

On Mon, 18 Jul 2005, Magnus Westerlund wrote:

> We chairs has already planned to use some of the AVT meeting time to
> discuss the issue of media types registration for RTP payload formats.

I won't be in Paris to join in this discussion, but I am fully in
agreement with Magnus and Colin that the media types registration
process should remain as it is with RTP types as part of the MIME
registry.

Since the registration template is being modified by
draft-freed-media-type-reg-04.txt to include a new "Restrictions on
usage" field, I have submitted an update to RFC 3555 to revise the
method for registering RTP payload type names accordingly.  This is
draft-ietf-avt-rfc3555bis-00.txt.  The "Changes from RFC 3555" section
states:

    This document updates RFC 3555 to conform to the revised MIME type
    registration procedures in [2].  Whereas RFC 3555 required the
    encoding considerations to specify transfer via RTP, that is now
    specified under restrictions on usage.  This document also adds a
    new Section 2.1 to clarify the requirements for sharing a MIME
    type among RTP and non-RTP transfer methods.

The section 2.1 says:

    The same MIME type MUST NOT be shared for RTP and non-RTP
    (file-based) transfer methods unless the data format is the same
    for both methods.  The data format is considered to be same if the
    file format is equivalent to a concatenated sequence of payloads
    from RTP packets not including the RTP header or any
    payload-format header.

    The file format MAY include a magic number or other header at the
    start of the file that is not included when the data is
    transferred via RTP.

    A second requirement for sharing a MIME type is that the sets of
    required parameters must be the same for both methods.

    For cases where the data format or required parameters cannot be
    the same for RTP and non-RTP transfer methods, then the data
    formats MUST be registered as separate types.  It is RECOMMENDED
    that the type names be related, such as by using a common root
    plus a suffix.

I think this is all consistent with the way we have been operating in
AVT for some time.  However, the second of those paragraphs may be
controversial outside AVT.

                                                        -- Steve

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