[asterisk-users] local channels and g729a voice quality

[Steve Underwood]

On 01/16/2012 03:59 PM, Roi Stork wrote:
> Hi,
>
> We noticed a very sharp drop in voice quality when using digium g729a
> codec. The problem seems to happen if the A channel (caller's channel)
> is a landline/mobile number contacted using the same outgoing provider
> (as a local channel). It sounds like listening to a mono speaker on
> low volume.
You have conflated two very different things there - landline calls and 
cellular calls. A land line to a VoIP user by G.729A should sounds 
pretty good. A cellphone to a VoIP user by G.729A should sound *far* 
worse. Converting between two different low bit rate codecs really hits 
the quality, and all cellphone calls are low bit rate.
> If I use a softphone that is directly registered to our asterisk box
> the audio quality improves, the words come out more clearer and
> louder.
You are conflating two things again. Quality and volume are largely 
independent issues.
> I also asked my provider to test call me using their Cisco as5300
> system and g729 codec and compared it with ulaw. The difference is
> unnoticable.
Try that again. If you really can't hear the difference you should check 
carefully that the system is working as you think it is. If it is, maybe 
you should consult a doctor. G.729A is considerably poorer than ulaw.

Steve