[Speex-dev] AEC: Tips on signal synchronization.

Jean-Marc Valin jean-marc.valin at usherbrooke.ca
Wed Dec 30 04:25:21 PST 2009

Maybe you shifted the signal too much. If the mic signal is just one 
single sample *ahead* of the playback signal, then there's no 
cancellation possible (because the system is not causal). Be careful 
with that. Otherwise, if could simply be dropped frames.


On 2009-12-30 07:06, Marco Pierleoni wrote:
> The problem is that now I have two files very similar (one for mic, the
> other for speaker).
> If I play them together I can hardly say that they are two different
> file for most of the file length.
> When I try to cancel the echo, I obtain as output almost the same input.
> The update_foreground variable is always 0. I don't get the conditions
> which must be fulfilled in order to have update_foreground=1.
> I see that there is some energy comparison, but I don't get the physical
> meaning of all the components.
> Is it normal to get always 0?
> If the track are into alignment, are there other tracks' properties to
> consider in order to get a good echo cancellation? Maybe the audio
> quality? or the relative volume?
> Thanks for any help.
> Marco Pierleoni.
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