Speex dev - Dec 2005 - AEC params

Hi:

Can anyone give some insight on:

1) As per the Speex manual, there is a mention of the
relationship between input frame and echo frame (Pg
19, Para 2). I was wondering of what would be the
ideal delay between these two frames, so that the echo
is already fed to the canceller and the echo
cancellation filter is not inefficient.

2) Corresponding to the above mentioned delay, what
filter length should we define while creating the echo
canceller state so that we can expect the AEC to
remove or reduce the echo.

Thanks
Su

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Le lundi 12 d?cembre 2005 ? 02:57 -0800, Suchibrata Kar a ?crit
:
> Hi:
> 
> Can anyone give some insight on:
> 
> 1) As per the Speex manual, there is a mention of the
> relationship between input frame and echo frame (Pg
> 19, Para 2). I was wondering of what would be the
> ideal delay between these two frames, so that the echo
> is already fed to the canceller and the echo
> cancellation filter is not inefficient.
Smallest as possible as long as your 100% sure that it's positive. In
practice, half a frame is good.
> 2) Corresponding to the above mentioned delay, what
> filter length should we define while creating the echo
> canceller state so that we can expect the AEC to
> remove or reduce the echo.
So far, my rule of thumb is to use about half of the 60 dB reverberation
time. For example, in a small room, the reverberation time is in the
order of 250 ms, so a tail length of 125 ms would be good.

	Jean-Marc

Hi:

I have been trying to test the speex AEC by playing a
voice sample (pre-recorded) as a echo and capturing a
new voice sample and playing the pre-recorded one, for
reference. [Sampling rate 8 KHz, frame size 64]

For some reason, I dont see any removal of echo. Does
anybody have a idea of * Testing the AEC in some other
mechanism
or
* Getting some sample files for testing AEC

Thanks
Su


--- Jean-Marc Valin <Jean-Marc.Valin@USherbrooke.ca>
wrote:
> Le lundi 12 d?cembre 2005 ? 02:57 -0800, Suchibrata
> Kar a ?crit :
> > Hi:
> > 
> > Can anyone give some insight on:
> > 
> > 1) As per the Speex manual, there is a mention of
> the
> > relationship between input frame and echo frame
> (Pg
> > 19, Para 2). I was wondering of what would be the
> > ideal delay between these two frames, so that the
> echo
> > is already fed to the canceller and the echo
> > cancellation filter is not inefficient.
> 
> Smallest as possible as long as your 100% sure that
> it's positive. In
> practice, half a frame is good.
> 
> > 2) Corresponding to the above mentioned delay,
> what
> > filter length should we define while creating the
> echo
> > canceller state so that we can expect the AEC to
> > remove or reduce the echo.
> 
> So far, my rule of thumb is to use about half of the
> 60 dB reverberation
> time. For example, in a small room, the
> reverberation time is in the
> order of 250 ms, so a tail length of 125 ms would be
> good.
> 
> 	Jean-Marc
> 

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