[Speex-dev] AEC learning behaviour

Andras Kadinger bandit at surfnonstop.com
Wed May 25 08:22:36 PDT 2011

2011.05.25. 4:52 keltezéssel, Arun Raghavan írta:
> On Tue, 2011-05-24 at 11:09 -0400, Jean-Marc Valin wrote:
>> The fact that the AEC takes a few seconds to converge is normal. The
> Do you think there might be a way to reduce this?
The shorter you make the tail length the faster it will adapt. But this 
will make it more important to reduce HW/SW latency so that you don't 
waste the first part of the tail length on latency that will never have 
useful audio to adapt on. Also be careful not to overcompensate for 
latency, because then the AEC will see the recorded echo before the 
played back signal, and it will break its assumption of causality (that 
is that the recorded signal does not come before the played back signal).
>> 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
>> response.
> I didn't see any abnormal behaviour from PulseAudio or the app
> corresponding to these resets. I'll try to see if I can pin down the
> actual cause.
> Thanks and cheers,
> Arun

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