[asterisk-dev] patch for silence

[yusuf]

Hi,

I have been researching, for the last few weeks, Discontinuous
Transmission (DTX), silence suppresion, Confort Noise Generation (CNG) and
Voice Activity Detection (VAD).  My purpose is simple: Bandwith in South
Africa is *very* expensive (SA is about 400% more expensive than other
countries).  My aim is to develop a patch(or group of patches) which will
provide Asterisk will the above functionality, which will save me about
40% to 60% on bandwith costs.  (I am in conjuction also incoporating in
Linux header compression, will will bring down  the header of every voice
packet down from 40 bytes to 2 bytes).  I am currently using the following
Asterisk patches: bug 5374, which allows Asterisk to communicate with
devices that support silence suppresion; bug 5409, comfort noise
generation in Asterisk; and bug 1234.  I have also studied all the
relevant RFC's on Speex, RTP, g723.1, g729.  I now have  reached the stage
where I need some help from the dev community.  What type of changes are
required in Asterisk for VAD and CNG to operate with speex, or any codec
that supports these features.  I think first of all changes to the RTP
stack, to support payload types for speex.  Can anybody please guide me on
what other issues are there to make Asterisk support silence suppression
with codecs that support it, like speex.  Can this also be possible on
where the ingress channel is ZAP (E1/PRI).

I would appreciate *any* help


thanks,
yusuf