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[AVT] Re: I-D ACTION:draft-herlein-speex-rtp-profile-02.txt

Greg, [cc IETF AVT mailing list]

On 5 Apr 2005, at 20:31, Internet-Drafts at ietf.org wrote:
A New Internet-Draft is available from the on-line Internet-Drafts directories.


	Title		: RTP Payload Format for the Speex Codec
	Author(s)	: G. Herlein, et al.
	Filename	: draft-herlein-speex-rtp-profile-02.txt
	Pages		: 15
	Date		: 2005-4-5
	
Speex is an open-source, patent-free, voice codec suitable for use in
Voice over IP (VoIP) type applications.  This document describes the
payload format for Speex generated bit streams within an RTP packet.
Also included here are the necessary details for the use of Speex with
the Session Description Protocol (SDP) and a preliminary method
of using Speex within H.323 applications.

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-herlein-speex-rtp-profile -02.txt

I have a few comments on this draft (see below). In general, I think it's a reasonable payload format, and would be appropriate as an AVT work item for eventual publication as a proposed standard RFC. If there are no objections from the group, I suggest you submit an update with filename draft-ietf-avt-rtp-speex-00.txt.

The description of use of the P bit in the RTP header notes that "P is set if the total packet size is less than the MTU". This makes it sound like P is always set when the packet is smaller than the MTU, whereas padding is actually very unusual. I suggest you remove that sentence, since the rest of the paragraph is sufficient without.

The use of the M bit in the RTP header to indicate comfort noise is unusual. Can you comment why it was used in this way, rather than being used to indicate the first packet after the "silence" period, as would be typical? The unusual semantics are not necessarily problematic, but we I'd like to understand what benefit we gain from the additional complexity of atypical usage.

Finally, I don't think it's appropriate for this draft to define how to use H.323/H.245 with Speex (since the ITU owns those protocols, not the IETF). Is it possible to remove sections 10-12 from future versions, replacing them with a reference to an external document (perhaps on the speex.org website)?

Colin


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