Sometimes not hear very well when make call gsm to gsm

Hi all,

i need same help , same customers complain nor hear very well i try modify RX and TX in chan_dahd.conf , but hit´s not enough.

This is problem in asterisk ?
Codecs ?
From the Cards ?


RX and TX are hardware gain settings increase/decrease the analog volume level on a channel. So I dont think it could be the issue of the Poor call quality, related to codec, this could impact the call quality if you re using Wideband audio codecs in a Low Bandwidth connection, also transcoding could be a factor some times depending on the system resources but as you are using dahdi instead of SIP I think the issue instead of codec could be hardware issue. anyway you could try differents codecs and see if you get better result or contact the card vendor for support

GSM sound quality is horrible at the best of times. If you can, try change the codec and see if that fixes it. That should tell you everything you need to know.

in this case the codec wich recommends ?

mulaw in North America and Japan and A-Law elsewhere, will give the best available quality if the PSTN is involved anywhere in the call.


I using pjsip and i set allow=ullaw , allow and gsm .

But same costumers complain

what i need to do ?