Re: [AVT] comments on draft-ietf-avt-rtp-speex-05.txt

[Jean-Marc Valin <jean-marc.valin at usherbrooke.ca>]

Alex Eleftheriadis a écrit :
> Given that the Speex bitstream is "embedded", in the sense that
> narrowband bitstreams are embedded in wideband bitstreams, has there
> been any thought on allowing each bitstream component to be transported
> over its own RTP session?
> 
> The structure appears similar - if not identical - to scalable coding,
> such as H.264 SVC, for which an RTP payload format is currently being
> developed. By separating the layers into their own RTP sessions, one can
> take advantage of the scalability of the codec in obvious ways (e.g.,
> receive only the streams that can/is willing to decode, works nicely in
> a multicast environment, can use different protection for the narrowband
> component, etc.).

No. This may make sense for H.264 which has huge data anyway (fragmented
into multiple packets), but the Speex data is tiny and fits easily into
one packet. Given the 16 kbps overhead of IP+UDP+RTP, it's just not
worth it. Also, Speex wideband is embedded, but not scalable. If you
peel something, it's only the high-frequencies. The narrwband part
remains the same.

	Jean-Marc


> I looked in the avt list archives going back quite a while, but did not
> find any discussion on this.
> -- 
> Alex Eleftheriadis
> alex at vidyo.com
> 
> 
> On Feb 28, 2008, at 7:57 AM, Aymeric Moizard wrote:
> 
>>
>> Hi all,
>>
>> We've delivered a new draft for speex codec recently.
>>
>> Following previous comments, the SDP usage part and
>> sample have been improved: more details and examples
>> have been provided.
>>
>> We do think this document is complete and hope to
>> have any comments!
>>
>> tks,
>> Aymeric MOIZARD / ANTISIP
>> amsip - http://www.antisip.com
>> osip2 - http://www.osip.org
>> eXosip2 - http://savannah.nongnu.org/projects/exosip/
>>
>>
>> On Sat, 16 Feb 2008, Internet-Drafts at ietf.org wrote:
>>
>>> A New Internet-Draft is available from the on-line Internet-Drafts
>>> directories.
>>> This draft is a work item of the Audio/Video Transport Working Group
>>> of the IETF.
>>>
>>>
>>>     Title           : RTP Payload Format for the Speex Codec
>>>     Author(s)       : G. Herlein, et al.
>>>     Filename        : draft-ietf-avt-rtp-speex-05.txt
>>>     Pages           : 23
>>>     Date            : 2008-02-16
>>>
>>> Speex is an open-source 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).
> 
> [snip]
> 
> 
> 
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