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[Barry Farber]

If my memory serves me right, the "codepoints" of 4 for G.723.1 and 18 for G.729
were added to H.225.0 a while ago to reflect text in the revised RFC 1890
mentioned by Steve Casner. At one point, the payload format descriptions also
matched, but I haven't compared the 2 documents lately to see if that is still
the case.

Glen


Stephen Casner wrote:

> On Wed, 23 Feb 2000, Chip Sharp wrote:
> > At 01:11 PM 2/23/00 -0800, Hutton, Charles wrote:
> > >I have the same concerns for G.729E.
> >
> > I'd recommend that as SG16 defines new encoding types that it register them
> > with IANA.
> >
> > Theoretically, someone could register your codepoints for a different
> > algorithm.
>
> No.  As I mentioned in my previous response, the registration policy
> has been revised.  There will be no more assignments of static payload
> type numbers because mechanisms are now in place in various control
> protocols to dynamically define payload type number bindings for each
> session.  It should be clear that static assignments cannot continue
> indefinitely in a small number space.  This rationale is explained
> further in section 3 of the draft revision of RFC 1890, which is
>
> http://www.ietf.org/internet-drafts/draft-ietf-avt-profile-new-08.txt
>
> My understanding is that H.245 provides a means to define dynamic
> payload types as part of the capability exchange using OIDs.  This is
> necessary for non-standard encodings, for example.  It should be used
> for future standard encodings as well to dynamically map from a larger
> encoding name space to the small payload type number space.
>
> In addition to whatever namespace(s) may be needed for ITU protocols,
> several IETF protocols use the MIME namespace, including the "rtpmap"
> attribute used for dynamic payload type mapping in SDP.  A few weeks
> ago, the IETF AVT working group sent a liaison statement to SG16 (or
> at least attempted to) via Joerg Ott to the Rapporteur of ITU SG16
> Q.13 to describe the procedure for defining new RTP payload formats.
> In particular, we encourage the registration of new payload formats in
> the MIME namespace according to the procedures in
>
> http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-mime-01.txt
>
> I don't know the details of G.729E.  If it requires a different
> payload format than G.729, then I would encourage you to let AVT
> review the payload format specification and that you register the
> payload format in the MIME namespace.
>                                                         -- Steve

--
Glen Freundlich                       ggf at lucent.com
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