[Speex-dev] AEC stops working in 1.2-rc1?

[Jean-Marc Valin]

OK, did another attempt with beta3 and *without* the preprocessor, I get
no cancellation at all. What this means is that there's something that
pretty much prevents cancellation but has a side effect that the
preprocessor is able to remove some of the echo. In 1.2-rc1, the
behaviour is a bit different, but fundamentally the problem is that the
AEC itself can't cancel much. The reason for that is not clear, but I'd
bet that something's wrong with your signal. What it is, I can't really
say, though.

	Jean-Marc


Benny Prijono a écrit :
> On Mon, Aug 11, 2008 at 12:34 PM, Jean-Marc Valin
> <jean-marc.valin at usherbrooke.ca <mailto:jean-marc.valin at usherbrooke.ca>>
> wrote:
> 
>     OK, here's what happens. There is indeed a small difference between
>     beta3 and rc1, but the fundamental problem isn't there. I've attached
>     plots of the speaker signal (blue) alongside the mic signal (green). You
>     can see the delay is in the order of 1000 samples. That's way too much
>     to do anything useful because the tail doesn't even "see" the echo. You
>     need to reduce that delay if you want the AEC to work. See the manual.
> 
> 
> Sorry I don't get you. I can make sense of that *if* you're talking
> about testecho sample application, since in testecho the tail is set to
> 1024 samples.
> 
> But, as I explained, I used my test program for producing the result,
> and there I set the tail length to 200ms (1600 samples). *And*, in
> addition to that, I delay the frames that's fed to
> speex_echo_cancellation() by 100ms, to reflect the playback/recording
> delay when the mic.pcm file was recorded. This means, if I play the
> frame now, I will give it to speec_echo_cancellation() 100ms later
> (similar to your PLAYBACK_DELAY in mdf.c). So this is equal to shifting
> the blue signal in your graph to the right by 100ms.
> 
> It's easier to understand with testecho perhaps. I did the following
> changes to testecho.c:
> 
>  - changed the frame size and tail length:
>     #define NN 80
>     #define TAIL 1600
>  - apply the delay before entering the "while" loop by adding:
>      {
>          int i;
>          for (i=0; i<10; ++i)
>            fread(ref_buf, sizeof(short), NN, ref_fd);
>      }
> 
> The result, testecho from beta3 can cancel the echo, while the rc1
> version can't.
> 
> I hope I made it clearer this time.
> 
> Thanks
>  Benny
>