[Asterisk-Users] Re: Asterisk Crackly Bad quality

[Rich Adamson]

> Thanks. On a related note.  The problem that I am troubleshooting has to do
> with an IAX connection to TELIAX.   Outgoing calls are perfect.  When I have
> incoming calls they are very crackly and break up.   I have checked the
> jitter buffer and it is not overrunning so it doesn't appear to be a jitter
> or packet loss problem.
> 
> I am beginning to suspect that since I don't have a ZAPtel card in my
> machine, * is losing sync with the incoming stream.  From what I understand,
> if there isn't a zap timing source * uses the incoming data stream to derive
> timing.  

The timing source that you're referring to is only needed for meetme conference
and a couple of other items like that. Has nothing to do with iax.

> Since the incoming stream is using VAD, my assumption is that it is losing
> the timing during the pauses in the speech.   Does anyone know of a way to
> just turn off VAD in *?   This would have multiple benefits (if you have the
> bandwidth).   Turning off VAD will improve voice quality by eliminating and
> front end clipping during talk spurts and I am assuming will also minimize
> the impact of not having a ZAP timing source.
> 
> Is there a way to disable VAD in *?

VAD would be the problem, and its not fixable at your * location since
you're receiving iax packets from teliax.com (at least that was my
understanding). 

The only solution you have is to convience the distant end to disable
silence suppression.  

There has been some discussion on and off for some time about changing
asterisk's VAD behaviour, but my understanding is that is a major effort
and not sure where it stands.

By the way, I'm a very happy camper with TELIAX.com and asterisk. Very
clear and solid audio using iax-gsm in both directions. Excellent
customer support to date, and I don't work for them. :)