[Asterisk-Users] Sipura g729 call quality to PSTN

[Pedro]

If this has been covered before - I appologize.

We use some Sipura SPA-2000's with the g711 codec and all seems fine
(except for the occasional failure to register errors in my asterisk
logs - but I will save that for another post).

g711 call quality is on par with our Cisco 7960's.  However, when
using the g729 codec, the call quality on the Sipura device goes
downhill on the PSTN side (the audio on the phone connected to the
Sipura sounds fine).  My guess is that the Sipura does not compress
the outbound audio very effectively and since the incoming audio from
the PSTN is already compressed by the VoIP provider, it is just
delivering the good-sounding g729 stream.

It is worth noting that call quality on both the IP and PSTN side is
great when using the Cisco 7960 with g729.  It is just with the Sipura
that the sound quality on the PSTN-side sounds like a bad quality cell
phone call.

I even got an SPA-2100 in hopes that the g729 would sound better on
that unit, but the same issue is present there as well.

Is it just a bad implementation of g729 compression with the Sipura
product line?

Any thoughts or recommendations are appreciated :)

Thanks!

- Pedro