[Speex-dev] Query on Speex Echo Cancellation Constraints

Ken Smith ken at alanta.com
Mon Mar 7 11:44:28 PST 2011

In my experience, the Speex AEC is one of the less-mature parts of the Speex
eco-system.  In my Silverlight/C# port of Speex 1.2RC1, after automated
tuning of every parameter I could think of, I could at best get something
like 65% of the echo removed.  However, if I combined it with the Speex
pre-processor with echo suppression enabled, it was much more usable: I
could achieve something like 90-95% of the echo removed.  There was
certainly some attenuation of the original signal, but the result was of
usable quality (if not really in the neighborhood of, say, what Skype is
able to achieve).

My recommendation would be to spend the time to create a test harness that
tries echo cancellation/echo suppression with every possible set of
parameters, and measure the actual results achieved.

Ken Smith
Cell: 425-443-2359
Email: ken at alanta.com
Blog: http://blog.wouldbetheologian.com/

On Mon, Mar 7, 2011 at 9:09 AM, KS <wakeup1504 at gmail.com> wrote:

> Hi,
> From the Speex Manual, section 6.2.1 (Echo Cancellation - Troubleshooting),
> it was mentioned that echo cancellation will not work if the playback and
> capture is done on 2 different soundcard. I would like to know whether this
> is true. I trying to use Speex Echo Cancellation on capture audio from a
> webcam mic with the playback through my onboard audio.
> Based on what is mentioned in the troubleshooting guide, does this mean
> that I would never be able to get the Echo Cancellation to work in my
> scenario?
> For my testing, I was using an echo tail length of 100ms and frame size of
> 20ms. Using this setting, I found that the echo cancellation does work, but
> it is too aggressive and cause the actual voice to get attentuation as well,
> resulting in audio distortion that sounds like audio drop. Increase the echo
> tail length to 120ms made the voice attentuation issue less severe, but
> resulted in much of the echo remaining in the audio.
> Does anyone have any advise on what I can look at and what parameters I can
> tweak to try to improve the Speex Echo Cancellation performance? I already
> using 1.2rc1. Thanks.
> regards,
> KS
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