[gst-devel] comfort noise generation bin

[Olivier Crête]

Hi,

On Mon, 2010-04-26 at 12:53 -0500, pl bossart wrote:
> >> > So maybe another solution is needed, like having the decoder generate
> >> > a
> >> > comfort noise buffer when they receive a "GstRTPPacketLost" event from
> >> > the jitterbuffer (which should be only sent to the last active payload
> >> > type per SSRC). My understanding is that the decoder should only
> >> > generate CN after their receive one SID frame until another voice
> >> > frame
> >> > is received. That said, this solution means that in a multi-party
> >> > call,
> >> > one would get CN.
> >>
> >>   You might be able to do this without resorting to a new event, but
> >> instead by having the jitterbuffer send new new-segments which is the
> >> technique we also use for sparse streams (i.e. the decoder sees a
> >> new-segment, knows that no data is available until a certain point and
> >> therefore pushes out comfort noise up to the new start position).
> >
> > Are you suggesting we have the jitterbuffer resend a newsegment event
> > every 20 or 30 ms ? Btw, that "GstRTPPacketLost" already exists in the
> > jitterbuffer.
> 
> SID and Packet losses are orthogonal concepts, this approach will not
> fly. SID is used to reduce the bandwidth when the Voice Activity
> Detection (VAD) on the transmitter side doesn't detect any speech to
> transmit. You can have regular or SID frames, and packet losses for
> both types for frames.

Oops, I though rtpjitterbuffer would generate a lost packet message
after a certain amount of time, but it seems to only generate it on the
next packet after a gap. So you are right, it is not a good solution.

I still think we need some kind of arbitration to not have more than one
decoder produce silence since Farsight2 will keep the previous decoders
if the sender starts sending on a new PT. That's why I wanted to do it
as late as possible (in the mixer). 

-- 
Olivier Crête
olivier.crete at collabora.co.uk
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