[Speex-dev] AEC learning behaviour

Stuart O. Anderson stuart at whispersys.com
Wed May 25 11:29:15 PDT 2011

Perhaps you could add a warm-start to the AEC, such that the parameters
start near the correct values on all but the first use?


On 05/25/2011 08:22 AM, Andras Kadinger wrote:
> 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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