[Speex-dev] Extracting Coefficients from the AEC

[Steve Underwood]

On 07/27/2011 06:17 AM, Cooper, Douglas A CIV NAVAIR, 4.6.2.3 wrote:
> Hello,
>
> I am new to this forum and have done my best to search for my answer before emailing, but have been unsuccessful. I have an application where I would like to utilize the speex AEC library for canceling hybrid echo.
The Speex echo canceller was designed to cancel room echoes. It is a 
poor choice to cancel hybrid echo. Try OSLEC. That is designed for 
hybrid echoes.
>   I thought it would be useful to save the coefficients of the filter for reuse, especially since the characteristics of the echo path will not vary.
Really? Do you call the same number every time, and through the same 
delay path?
>   The specific application for the hybrid scenario consists of a "side-tone" producing device (e.g. radio) connected to a full-duplex interface which connects to a digital voice network. It isn't a show stopper if this in not a capability, but in the event my system or software was reset, it would be nice to not have to reconverge every time (i.e. intialize the adaptive filter to a non-zero state).
The far end hybrid and telephone is a big part of your total echo, so 
you will need to readapt each time. The last set of coefficients may not 
even be a very good starting point for readaption.

Steve