[Speex-dev] AEC gets worse as sample rate increases

Mihai Balea mihai at hates.ms
Mon Dec 10 14:23:54 PST 2007

On Dec 10, 2007, at 5:11 PM, Jean-Marc Valin wrote:

> Try using SPEEX_ECHO_SET_SAMPLING_RATE to specify your sampling rate.
> Also, don't forget that the tail need to be longer (proportional to  
> the
> sampling rate). Last thing, if you use resampling, make sure you use a
> decent resampler (the Speex one is fine) because otherwise, any  
> aliasing
> left will not be cancelled.

Hi Jean-Marc,

Thanks for your prompt reply.

We are using SPEEX_ECHO_SET_SAMPLING_RATE to set up our EC with the  
correct sample rate and we also set a tail that is proportional to  
the sample rate.  By the way, would having a tail length that is not  
a power of 2 impact the quality of the EC or just the CPU performance?

We are using resampling but the resampling stage is set up before the  
EC.  To  be more specific, we decode, upsample, pass it to EC and  
then send it out to the hardware.  On the way back in we do EC,  
preprocess, downsample back to 8K and encode. We use the speex  
resampler at VOIP quality (I believe that is 3).

Do you see any potential issues with this setup? Is there anything  
else you would suggest we try?

Thanks again,

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