Speex dev - Aug 2006 - How to use aec correctly?

Hi,all
  I have tested AEC on files, it works well.I have some files,one is echo
file, others are echo-added files(an origin file adding echo at different
delay,such as 20ms,40ms...120ms,140ms).AEC do wonderfully on those files
except echo added at 140ms-delay.
  But ,when i use AEC in my voip project, it does feebly. Who can give me
some hints why caused this.How long can  sound be picked up by mic after it
plays out.This is the main problem to align echo.Give me a hint.
Best regards
keith

On Tue, 2006-08-08 at 17:38 +0800, keith wrote:
> Hi,all
>   I have tested AEC on files, it works well.I have some files,one is echo
> file, others are echo-added files(an origin file adding echo at different
> delay,such as 20ms,40ms...120ms,140ms).AEC do wonderfully on those files
> except echo added at 140ms-delay.
The longer the delay, the smaller the "effective" part of the filter
(tail).
>   But ,when i use AEC in my voip project, it does feebly. Who can give me
> some hints why caused this.How long can  sound be picked up by mic after it
> plays out.This is the main problem to align echo.Give me a hint.
What I recommend: 
1) Read the *new* version of the manual (the one on the website hasn't
been updated in a while)
2) record your input and output to a file so you can look at them and
perform AEC offline (i.e. you can actually see what happens)
3) Have a look at Echo Cancellation Demystified
http://www.embeddedstar.com/articles/2003/7/article20030720-8.html

	Jean-Marc

Hi,

For me AEC fails terribly on Dell Axim PDA. It has a high nice 625
Mhz processor.

AEC for me works on desktop. I maintain a queue of packets played on
speaker and a queue of packets captured through mic. These queue are
requirde since I am using Windows waveform APIs which behave in an
unexpected manner, as they are callback oriented. But with the
queues in place you can get the syn down to a level where a tail of
12*160(160 is the number of samples) , actually lesser, so it works
on a desktop.

Point to note is that I need to use speex_preprocess call otherwise
there is a trail of echo remaining which when high gets amplified
on each succesive pass.

On a PDA with only the call to speex_echo_cancel, the whole thing
becomes so slow, that wit just does not work.

I am using latest speex from SVN and fixed_point compilation on a
Dell Axim PDA (which looks like having some nice processing power
as compared to other PDAs)

Any advice on why speex_echo_cancel call takes so long, messes up
the normal packets also without any echo (wear headphones).

Thanks
-Anurag


Quoting keith <qzyxm@126.com>:
> Hi,all
>   I have tested AEC on files, it works well.I have some files,one
> is echo
> file, others are echo-added files(an origin file adding echo at
> different
> delay,such as 20ms,40ms...120ms,140ms).AEC do wonderfully on
> those files
> except echo added at 140ms-delay.
>   But ,when i use AEC in my voip project, it does feebly. Who can
> give me
> some hints why caused this.How long can  sound be picked up by
> mic after it
> plays out.This is the main problem to align echo.Give me a hint.
> Best regards
> keith
>
>
>
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