[Asterisk-Users] VAD/DTX implementation through zaptel cards

[Eric Wieling]

The only time PLC makes sense is thwn you are converting FROM VoIP to 
something else.  So PLC would be done on chan_sip or chan_IAX, or 
chan_h323 on the receiving end.  This is for 1.0.x.

For CVS-HEAD you would want to do this on the receiving side in the 
PLC stuff.

parijat wrote:

> Hi,
> Thanks for helping me out.
> 
> I want to clear out few more points
> 
> 1) zaptel cards receive PCM from PSTN. In what form do they give it to
> asterisk. Do Zaptel cards CODE/DECODE PCM from PSTN to RTP or zaptel cards
> forward PCM to asterisk which converts it to RTP.
> 
> 2) If asterisk does that conversion then, using which file 
> does it convert. I want to change code of that file so that I can implement
> VAD.  
> 
> 3) If all this is not possible then why they have give so many codec files
> in asterisk.
> 
> Regards,
> Parijat
> 
> -----Original Message-----
> From: asterisk-users-bounces at lists.digium.com
> [mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Steve
> Underwood
> Sent: Tuesday, April 12, 2005 9:40 PM
> To: Asterisk Users Mailing List - Non-Commercial Discussion
> Subject: Re: [Asterisk-Users] VAD/DTX implementation through zaptel cards
> 
> Steve Kann wrote:
> 
> 
>>Eric Wieling wrote:
>>
>>
>>>parijat at varaha.com wrote:
>>>
>>>
>>>>Hi,
>>>>How can i implement VAD/DTX using zaptel with asterisk towards PSTN. 
>>>
>>>
>>>
>>>TDM (PSTN/telcos) do not support VAD. The entire idea of VAD is not 
>>>even a valid idea.
>>
>>
>>Doing VAD on audio coming _from_ the TDM world certainly is something 
>>you might want to do, to dramatically reduce the bandwidth you consume 
>>when sending the audio via VoIP channels.
>>
>>This kind of thing is not presently implemented in *, though, but it 
>>could be. (note: doing it well will require a bunch of CPU, though. I 
>>wonder if it could be done in the same DSP that is doing 
>>echo-cancellation on the new TE4xxP boards?
> 
> 
> Unless Digium's plans changed since the last time I spoke to Mark, the 
> answer would be no. I believe they are using a dedicated function echo 
> canceller device.


-- 
Always do right. This will gratify some people and astonish the rest.
Mark Twain