[Speex-dev] Using AEC on a mobile device where earpiece is routed differently

Omer Gilad Omer at fring.com
Mon Jan 18 00:47:33 PST 2010


I'm using AEC for a VoIP application on mobile handsets. I am doing
experiments to learn how to work with it, and I have a problem:

As long as I play through the device's normal speaker and record using
the mic, I have absolutely no clock drift (according to
echo_diagnostic.m). The echo is being cancelled and all is fine. Once I
route to the earpiece (and still use the mic, which is the only option),
no echo is cancelled and the diagnostic shows that I have clock drift.

I know that the AEC expects a locked clock, but that's my current
situation and I couldn't find any way to record from the same earpiece
soundcard (or whatever the internal implementation is). 

Is there a good way for compensating for that?

Could you also explain more thoroughly the concept of clock drift, as I
couldn't find much detail about it?



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