[Speex-dev] Echo Can Tail Length

David Baker dbkr at mxtelecom.com
Mon Apr 20 03:16:53 PDT 2009


I've been trying to understand the documentation on the Speex echo  
canceller, and unless I'm confused, I think there's a mistake  
somewhere. The documentation on http://speex.org/docs/manual/speex-manual/node7.html#SECTION00740000000000000000 
  says, " The recommended tail length is approximately the third of  
the room reverberation time". However, the Octave script  
echo_diagnostic.m has the code:

if (b > .3*tail_length)
       printf ('This is too much delay, try delaying the far-end  
signal a bit\n');

This seems to mandate that the tail length should be at least 3 (or  
3.33...) times the delay, which conflicts with what the manual says.

Is this a mistake, or is my understanding incorrect (I'm assuming that  
far-end delay and room reverberation time are the same thing). I'd  
really appreciate if someone could clear this up, as I've not had much  
luck getting the echo canceller to work.

Thanks in advance,


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