Speex dev - Dec 2005 - Visualizing echo

Hi,

I've added visualization of the speex noise cancellation to my program.

I did this by taking st->noise[] and st->ps[], scale both by 
1.0/(st->ps_size * 32768.0) (to get a value between 0.0 and 1.0), and then 
draw them as a realtime lineplot. This works well, and my users like being 
able to see roughly what frequency bands they have noise in and compare 
it to their input signal. It also settled the long argument I had with a 
user of whether or not 44.1 khz sampling was needed for human speech... 
And most of all, it's cool ;)

Now, I'd like to do the same for echo cancellation, but there I'm a bit
at
a loss of what arrays to look at and what values I should expect. Ideally, 
I'd like something like 'amount of echo in frequency band x at time 
offset y'.. Any idea of what arrays I should look at?

> Now, I'd like to do the same for echo cancellation, but there I'm a
bit at
> a loss of what arrays to look at and what values I should expect. Ideally, 
> I'd like something like 'amount of echo in frequency band x at time
> offset y'.. Any idea of what arrays I should look at?
You could look either at the y signal that gets subtracted from the
input, at the "residual echo estimate" that gets passed to the
preprocessor, or at the leak_estimate variable that says what fraction
of the echo is left (e.g. leak_estimate = 0.1 means 10dB echo
attenuation).

	Jean-Marc