[speex-dev] More Speex (pre-processing) Options

Tom Grandgent tgrand at canvaslink.com
Wed Nov 26 05:28:59 PST 2003

I don't think the echo canceller works yet.  The best I could 
get it to do is trash my audio.  If it does work, some sample 
code demonstrating its use would be really appreciated...

Here is what Jean-Marc has said about it in the past:

> What should I use for a filter length for speex_echo_state_init()? 

"Well, it depends on your problem. The filter length represents the
maximum delay of the echo. For acoustic echo, that value is generally
higher than for line echo. You'll need to experiment, but a value around
500 (for 8 kHz) might be a good start."

> [question about params for echo canceller function]

"Actually, ref is the incoming frame (with echo), echo is the outgoing
frame (that has only the echo) and out is the echo-cancelled frame. As
for Yout, it is an estimation of the residual echo that can be sent to
the denoiser so that residual echo can be removed as well. Note that
this last feature is still experimental."

<p>Tom Harper (harper at archila.com) wrote:
> Hi,
> So I have had a chance to delve deeper into  the new pre-processing
> code-  I was also able to get VAD, AGC, Denoising, etc working inside of the
> current release candidate (1.0.3).   For some reason, the 1.1.2
> release didn't properly encode/decode in our system (on windows)
> and I haven't had time to determine why.  In any case, all of the features
> jointly work very well- great job!
> I realize the echo cancellation element may still be in development, but I am
> having trouble getting that part of the preprocessor to work.  When
> I don't pass NULL into the speex_preprocess for the echo parameter, things
> seem to go haywire- some memory appears to be getting trampled somewhere
> (this is probably my fault).  Maybe I am misunderstanding the purpose of this
> parameter?  Except for the first few packets, the preprocessor
> appears to be removing all audio- The algorithm I am using passes in a recently
> decoded frame...  Any ideas?  Do I need to set some settings in somewhere
> in order for this to work properly?
> Thanks,
> Tom 

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