digital audio paths (Was: Re: Experimental technique for testing call audio quality? )

Stefano Cavallari stefano at
Sat Jan 23 02:28:32 CET 2010

On Friday 22 January 2010 20:13:58 Timo Juhani Lindfors wrote:
> Helge Hafting <helge.hafting at> writes:
> > the same quality as this, by tweaking volume settings. Calls are digital
> The audio data is fed to the GSM chip in analog form however.
> > If the FR sound quality is too bad, consider a BT headset. Sound quality
> > should then depend on the BT headset only. The FR's problems with buzz,
> > bad bass, and possibly other analog issues shouldn't matter at all.
> Even in this case the audio is fed in analog form to the GSM chip.
Why on hell GSM chips are still done this way?
I hope whatever next open phone comes around it's totally digital.
Audio lines maybe were a good idea for phones with few cpu power available, 
but now it's only a waste of PCB space I think. 
The hardware becomes more flexible and maybe you can do some DSP to enhance the 
voice. Or implement an answering machine inside the phone. 
Do anyone know about recent GSM chips? I'm still dreaming a up-to-date open 
phone :)
Is there a standard to do voice-audio-codec over multiplexed AT channel?
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