[Speex-dev] AEC learning behaviour

Jean-Marc Valin jmvalin at jmvalin.ca
Tue May 24 08:09:30 PDT 2011

The fact that the AEC takes a few seconds to converge is normal. The  
fact that it needs to completely re-converge in the middle of a call  
probably indicates that something went "wrong" in the audio  
capture/playback. For example, that could be an overrun/underrun in  
the soundcard buffer, or the user changing a volume control after the  
AEC, or moving the speakers, ... anything that changes the impulse  


Arun Raghavan <arun.raghavan at collabora.co.uk> a écrit :

> Hello,
> We've integrated the speex echo canceller into PulseAudio, and coupled
> with the AGC/denoiser, it works reasonably well and has been a breeze to
> plug in, so thank you!
> One thing we're seeing, though, is that the canceller seems to take some
> time (a few seconds) to "learn", so initially the echo is clearly
> audible and it slowly fades out. This sometimes occurs in the middle of
> a call as well (the echo becomes loud again and fades away in a few
> seconds).
> With the echo suppressor enabled, the learning time seems to drop, but
> the final echo remains higher than without suppression, and is still
> sufficiently audible to be annoying.
> Is this known behaviour? Any clues w.r.t. what might be going wrong?
> Cheers,
> Arun
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