Speex dev - May 2011 - pre-processor's residual echo suppression and AEC order

Hi,

Arun and me are working on a echo-canceler module for pulseaudio build around 
speex. When using the preprocessor's echo filter, specifically in
combination
with denoise and AGC, it's unclear whether these have to run before or after
the AEC.

Right now we've got one instance of speex_preprocessor doing AGC and denoise
running before the echo canceler; and a second for echo suppression after the 
echo canceler. This seems to have effect, but we have not tested the total 
quality of this configuration yet.

In the code however preprocessor.c compute_gain_floor() both noise and echo 
variables, suggesting these belong together in the same instance.

So is speex_preprocess_run always supposed to be run *after* 
speex_echo_cancellation, does it perhaps depend on which filter function is 
enabled?

Thanks
Bart

The echo canceller (AEC) should be run first on the recorded signal. 
Only do denoise and AGC and others after AEC - otherwise whatever you 
did (e.g. denoise, AGC, etc.) will only confuse the AEC.

Look under http://ns.surfnonstop.com/~bandit/speex/echocard1/ example 6 
to have an idea about what quality to expect.

2011.05.25. 14:49 keltez?ssel, Bart Cerneels ?rta:
> Hi,
>
> Arun and me are working on a echo-canceler module for pulseaudio build
around
> speex. When using the preprocessor's echo filter, specifically in
combination
> with denoise and AGC, it's unclear whether these have to run before or
after
> the AEC.
>
> Right now we've got one instance of speex_preprocessor doing AGC and
denoise
> running before the echo canceler; and a second for echo suppression after
the
> echo canceler. This seems to have effect, but we have not tested the total
> quality of this configuration yet.
>
> In the code however preprocessor.c compute_gain_floor() both noise and echo
> variables, suggesting these belong together in the same instance.
>
> So is speex_preprocess_run always supposed to be run *after*
> speex_echo_cancellation, does it perhaps depend on which filter function is
> enabled?
>
> Thanks
> Bart
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