[Speex-dev] DC component coming back after AGC

[Aymeric Moizard]

On Wed, 27 May 2009, Jean-Marc Valin wrote:

> I'm getting confused, what's the problem exactly? The AGC doesn't remove 
> the DC or it adds one?

Hi Jean-Marc, sorry for confusion:

Without the AGC, speex preprocessor is removing the DC.
With the AGC, speex preprocessor is adding a DC.

Here are the sample files:
http://antisip.antisip.com/tmp/

The first one contains very low signal with a DC.
The second one (16KHz, mono, 16bit) contains
the output after using a modified testdenoise.c with AGC
enabled and agc_level set to 20000.0 and configured
to operate on 16KHz file.

tks,
Aymeric MOIZARD / ANTISIP
amsip - http://www.antisip.com
osip2 - http://www.osip.org
eXosip2 - http://savannah.nongnu.org/projects/exosip/


> 	Jean-Marc
>
> Aymeric Moizard a écrit :
>> Hi Jean-Marc & all,
>>
>> I'm currently working on a wav file with very low volume.
>> This wav also contains a DC component.
>>
>> Using testdenoise with modification (AGC turned on with
>> 20000.0 value) I'm able to increase volume, but a new
>> irregular DC component appears again due to the AGC.
>> (seems to increase at the same time the AGC gain is increasing)
>>
>> Using testdenoise again on the output, but without the
>> AGC, the preprocessor remove the newly introduced DC
>> component.
>>
>> Note that the input has really low volume which is most
>> probably the main issue here. Still this is showing that
>> using the AGC potentially introduce DC component? Any
>> comment?
>>
>> Tks,
>> Aymeric MOIZARD / ANTISIP
>> amsip - http://www.antisip.com
>> osip2 - http://www.osip.org
>> eXosip2 - http://savannah.nongnu.org/projects/exosip/
>>
>> _______________________________________________
>> Speex-dev mailing list
>> Speex-dev at xiph.org
>> http://lists.xiph.org/mailman/listinfo/speex-dev
>>
>>
>