Maybe you've gotten used to the superior sound quality freeswitch provides :-)

Your audio quality is dependent on the equipment you are using, and the E1550 is a good piece of equipment. Check your signal stregnth and make sure you are giving the equipment the best chance of working. If that device doesn't have an external Jack then USB port extenders work wonders. Just remember that GSM isn't a high quality codec.

If your phones take GSM (most IP phones do) then make sure GSM is being used end to end (I.e. no transcoding). That might yield better sound quality, and you should be doing this to decrease the load being placed on your system.

No, there is no transcoding to/from GSM codec with mod_gsmopen.

mod_gsmopen takes a digital stream in signed linear (SL16) at 16 bit, 8 khz directly from the modem. It's the modem chipset that digitally converts from GSM codec to signed linear. So, mod_gsmopen passes to FreeSWITCH the SL16 stream 8khz, without touching it, in its purest form.

But it's true that if you're used to use FreeSWITCH with 16khz (or superior) codecs, then you can be spoiled ;).

-giovanni

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