[Speex-dev] Help needed for echo cancellation

Steve Kann stevek at stevek.com
Wed Jul 27 07:50:59 PDT 2005

Shantanu Gramsci wrote:

> Hello all,
> I use speex as codec [narrowband and wideband], echo canceller and 
> preprocessor. I was able to use it in all case except in echo 
> cancellation.
> I found that in my application, echo cancellation works only if echo 
> tail [echo filter length] is arround 2000 ms or more. But recomended 
> value in the documentation is 100 ms. With 2000 ms echo tail echo 
> cancellation works fine but it takes huge CPU and in some low 
> configuration computers face capturing problem, consequently sending 
> bitrate falls.
> Can any one put some light on this issue, why my echo cancellation 
> does not work with the recomended value of 100 ms or 160 ms?

Perhaps because there's a long delay between the actual audio 
source/sink, and when the ec sees the buffers.

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