[xiph-rtp] Speex -02 feedback and m bit question.
phil at plus24.com
Thu Apr 14 15:00:42 PDT 2005
You have probably seen Colin Perkins' feedback on the AVT list regarding
the -02 Speex draft. Having it move to WG status for the next revision
is great news!
One of Colin's questions:
> 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.
From the draft we specify:
The M bit indicates if the packet contains comfort noise. This field
is used in conjunction with the cng SDP attribute and is detailed
further in section 5 below. In normal usage this bit is set if the
packet contains comfort noise.
cng: comfort noise generation - either 'on' or 'off'. If off
then silence frames will be silent; if 'on' then those frames will
be filled with comfort noise.
Should this really conform strictly to the RTP specs or is this a case
where the RTP transportation needs to bend towards the encoder?
I think his other points, fixing the p bit and moving the ITU related
text to the speex.org site are fair and should pose no problems.
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