[Speex-dev] AEC troubleshooting

Aaron Drew aarond10ster at gmail.com
Wed Aug 12 02:42:34 PDT 2009

I've been playing with this as well. My laptop speakers are quite "tinny"
sounding and I get very different real-world results with this laptop than
with desktop speakers. Works great with decent speakers and a mic, works
terrible with my laptop (Lenovo Thinkpad SL400) built-in mic and speakers.
With my Lenovo's built in speakers and mic I eventually get a high pitched
"woot woot" creeping in (probably creeps in and out due to auto gain
settings I am using?) I'd like to add to these questions if I may:

3. Can choosing a "bad" sample size introduce artifacts due to windowing
problems with the Fast Fourier Transform required to do echo cancellation? I
mean, if I choose a sample size of 161 samples instead of say 1024, will
that affect the echo cancellation in some way.

On Wed, Aug 12, 2009 at 4:46 PM, Greger Burman
<greger at mobile-robotics.com>wrote:

> First of all, thank you for your input Tim. That is very helpful.
> I would love to hear from other people with experience of AEC and Speex.
> I guess I have to split my question into to parts now.
> 1.
> Is it a fact that using the windows multimedia API (wave audio) for audio
> capture and playback makes it impossible to do echo cancellation with Speex
> AEC or other EC method due to inprecise timing?
> I welcome comments from anyone who has got echo cancellation working when
> recording through WinMM, DirectSound or ASIO.
> 2.
> What about the Speex echo cancellor and the different sampling rates. Will
> it only perform well in narrowband mode (8kHz)? Does it not perform well in
> wideband (16kHz) or ultra-wideband (32kHz) mode?
> I read somewhere that you need a longer tail length for higher sample
> rates. Measured in samples it will of course be longer, but it could be
> interpreted as longer measured in milliseconds for higher sample rates.
> Someone please clarify.
> //Greger
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