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

[Steve Kann]

On Apr 13, 2005, at 8:36 AM, Eric Wieling wrote:

> 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.

I don't even see where PLC was mentioned in this thread..

PLC is orthogonal to VAD/DTX.

-SteveK



> 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
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