[Stox] stox-media: format parameter translation

Jonathan Lennox <jonathan@vidyo.com> Thu, 09 January 2014 17:22 UTC

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From: Jonathan Lennox <jonathan@vidyo.com>
To: "stox@ietf.org" <stox@ietf.org>
Thread-Topic: stox-media: format parameter translation
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Date: Thu, 9 Jan 2014 17:22:02 +0000
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Subject: [Stox] stox-media: format parameter translation
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This is the issue I brought up at the Interim -- I'll try to put it in writing.

The point I raised is that the stox-media draft's section on format parameter translation should try to focus on media types which are actually used by existing, deployed Jingle clients, since this is probably a relatively small set.  The important question is which payload formats in use by existing Jingle clients have SDP fmtp formats that don't follow the normal semicolon-separated parameter model.

I of course haven't done a full inventory of such payload formats, but two that seem reasonably likely and I think should be particularly called out are:

audio/telephone-event: RFC 4733: the fmtp contains the value of an implicit "events" parameter.

audio/red: RFC 2198, with its media type registration in RFC 3555: the fmtp is the payload types of the encompassed formats.  The RFC 3555 definition of the actual media type parameters is weird (in an attempt to make it self-contained), and I doubt that any Jingle client that does RED would actually use it that way. So we need to figure out what any actual Jingle implementations do.

Does anyone have a reasonably-authoritative list of which RTP payload formats are supported by existing Jingle clients?  Does anyone know of any other real-world usage of codecs that have unusual fmtp encodings?  Someone on the call mentioned that they thought that Speex's was weird, but as far as I can tell, it's a normal semicolon-separated encoding.