[Speex-dev] echo cancellation

[hs]

> echo cancellation:
> speex_echo_cancel (st, ptr, echo1[0], e_buf, noise);
> speex_preprocess (den, e_buf, noise);
>
> where ptr is a buffer that was recorded from microphone, echo1[0] is a  
> buffer that was played on loudspeakers. the delay between ptr and echo1  
> is 2 buffers (512 samples).
> with this configuration I can still hear the echo signal (althought the  
> signal is a little more silent. when using the delay 3 buffers the echo  
> is still not cancelled and after few seconds I don't hear anything.
when using about 10 buffers for delay between these signals the echo  
signal is heared as it was reverbed, everything else is ok and the noise  
is removed.
how to completely remove the echo signal?

regards
hs