[Speex-dev] AEC troubleshooting

Tim Na hna at alu.edu
Tue Aug 11 14:31:39 PDT 2009

Well, I am not the person to be asked about how Speex AEC works :)
And I was referring speaker input as having direct access into what has been
played thru speaker. (ASIO Soundcard provides interface for that)
So if I am remebering correctly, with data from Mic and Speaker in sync,
speex AEC should do the job. 


From: Guilherme Balena Versiani [mailto:guibv at comunip.com.br] 
Sent: Tuesday, August 11, 2009 1:33 PM
To: Tim Na
Cc: 'Greger Burman'; speex-dev at xiph.org
Subject: Re: [Speex-dev] AEC troubleshooting

Hello Tim,

Please explain exactly what you are meaning by "expose speaker input as
other OS". Did you reference system latency? If you do so, I would like to
understand better how the acoustic echo cancellation works, regarding the
latency between the audio reprodution and the acquired audio (I had problems
with that in the past, so I forgot the use of Speex mechanism for doing AEC
for VoIP systems).

In short: does Speex AEC have some kind of delay limit between the voices
(the input and the output)?

Best regards,

Guilherme Balena Versiani
Software Architect

 <http://www.comunip.com.br>  Rua Alvarenga Peixoto, 295 / 5º andar
Lourdes - CEP 30180-120 - Belo Horizonte, MG
(31) 3275-2220 9992-1578 

Tim Na escreveu: 

Ok, let me be more clear on this.
AFAIK, Windows OS doesn't expose speaker input as other OS ( Linux, Mac
OS...). That puts you in bad spot in using Speex AEC with windows.
Only way to work is to use Soundcard with ASIO functionality which does give
you speaker input.  But then you would have to impose that requirement on
all your users.
I heard Speex AEC works great from developer who used windows with ASIO
Vista AEC DMO or XP DirectSound AEC function does reasonable job and that's
what I am currently using.


From: speex-dev-bounces at xiph.org [mailto:speex-dev-bounces at xiph.org] On
Behalf Of Greger Burman
Sent: Tuesday, August 11, 2009 1:15 AM
To: speex-dev at xiph.org
Subject: Re: [Speex-dev] AEC troubleshooting

I actually forgot to mention that I'm using ultra-wideband mode, but seems
like you understood that anyway. Is this true that Speex echo cancellation
only performs well in narrowband mode !? 
I've been using 100 ms as the default tail length. I don't know what the
ideal tail length would be. I have tried shorter and longer tails but it
hasn't made any difference.
Does DirectSound's AEC perform well with high quality recording? Is it the
general opinion that it performs significantly better than Speex AEC?
2009/8/10 Tim Na <hna at alu.edu>

If you search the mail archive, you will see that people were only
successful using narrowband with long tail length.
Unless you have speaker input in perfect sync with mic input, it is
difficult to use Speex AEC.
If you don't have restriction on using Vista's AEC DMO or XP"s DirectSound,
I would recommend using those.


From: speex-dev-bounces at xiph.org [mailto:speex-dev-bounces at xiph.org] On
Behalf Of Greger Burman
Sent: Monday, August 10, 2009 5:40 AM
To: speex-dev at xiph.org
Subject: [Speex-dev] AEC troubleshooting

I'm experiencing little to no damping of acoustic echo from the echo
cancellor and I can't figure out why so far. I thought I should try the
echo_diagnostic tool so I built libspeex.dll and libspeexdsp.dll with the
DUMP_ECHO_CANCEL_DATA flag, but I'm not getting any output files at runtime.
Any ideas?

Build information:
Speex version: 1.2rc1
Target Win32 x86
MS VC++2008 EE
Configuration: Release, Full optimization, _USE_SSE

Greger Burman



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