[Speex-dev] Backup Echo Suppression

[Coffey, Michael]

I realize that the preprocessor echo suppression is not designed
specifically to counter the effects of data loss. On the other hand, as
much as I might like to, I do not have the option to "fix that problem
for real." The sad truth is that some end users have systems that may
drop samples, or do other unfathomable things, no matter what I do. I
can not rewrite their drivers, firmware, or operating system. My job is
to do the best I can in a difficult situation.

At this point, the echo canceller seems to work well on literally 90% of
the machines I have tested. I am trying to put together a "backup"
strategy to cover the cases where it does not work. I might eventually
settle for detecting non-convergence and enforcing half-duplex in that
case, but I'd like to better than that if I can.

I initially assumed that the echo suppressor is similar to other echo
suppressors (also called "nonlinear processors" or "loss controls").
Those suppressors use cruder algorithms that exhibit artifacts but that
may not depend on the fine time structure of the audio signals. Is this
not true of the preprocessor echo suppressor?

-mjc

-----Original Message-----
From: Jean-Marc Valin [mailto:jean-marc.valin at usherbrooke.ca] 
Sent: Tuesday, June 26, 2007 8:49 PM
To: Coffey, Michael
Cc: speex-dev at xiph.org
Subject: Re: [Speex-dev] Residual Echo Suppression by the Preprocessor

The residual echo suppression is supposed to be working decently well
now. However, it's not designed to counter the effects of samples being
dropped off the soundcard. You'll just need to fix that problem for
real.

	Jean-Marc