Acoustic Echo Cancellation

Florian Hackenberger f.hackenberger at
Thu Aug 28 08:39:26 CEST 2008

On Wednesday 27 August 2008, Al Johnson wrote:
> I assume you mean for GSM. I haven't heard anything about a roadmap
> for it, but it had occurred to me as a possibility. The audio routing
> looks possible - send the mic to the left ADC and the GSM output to
> the right ADC to collect the signal, remove the echo from the mic
> signal and send it out through one of the hifi DACs to the mono
> output. The GSM output can carry on to the speaker, headset or
> whatever as it does now.
Ok, that's good to know. I read through the docs on the audio subsystem 
but I was not sure if processing the mic output before passing it to 
GSM would work. However, I read on the hardware mailing list that the 
TI Calypso (GSM chipset) has echo suppression features which seem to be 
unused (or not correctly configured) at the moment. I don't know if 
other GSM handsets implement echo cancellation or if echo suppression 
is sufficient. Does someone know how to modify the qtopia phoneserver 
to send custom AT commands before answering a call? Simply enabling 
echo suppression would be so much less work than implementing an AEC.


DI Florian Hackenberger
florian at

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