Speex dev - Sep 2008 - Newbie: Get echo cancellation level

Hi:

I'm using speex to perform echo cancellation in Windows. I'm aware of
the problem about out of sync clocks in record and play sample rates in usual
sound cards . In order to have an idea of how good is my echo cancelation
working I would like to know if there is any #define thing i can pass to
speex_echo_ctl to get the actual level of echo cancellation. If not, how can i
extract that value from the library?
By the way, is any software solution for out of sync problem ? I'm trying to
keep input and output buffers adjusted by resampling, but it does not work well.

Thanks



      
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p_j_r_m a ?crit :
> I'm using speex to perform echo cancellation in Windows. I'm aware
of
> the problem about out of sync clocks in record and play sample rates in
> usual sound cards . In order to have an idea of how good is my echo
> cancelation working I would like to know if there is any #define thing i
> can pass to speex_echo_ctl to get the actual level of echo cancellation.
> If not, how can i extract that value from the library?
You can look at st->leak-estimate within mdf.c, but it's not exposed
through the API and is *very* approximate (if I really knew how well the
AEC was doing, I could cancel much better). A value of 0 for
leak_estimate means "perfect cancellation", while a value of 1 means
no
cancellation. Then, .1 means -10 dB and so on.
> By the way, is any software solution for out of sync problem ? I'm
> trying to keep input and output buffers adjusted by resampling, but it
> does not work well.
That approach would be really tough at best. Just not worth spending my
time on it.

	Jean-Marc

To cut down on jitter due to buggy software resampler code distributed by
Microsoft a number of years back that is used in many sound card drivers, it
is recommended that your input and output sample rates to/from the devices
be at the internal sample rate that the sound card operates at -- typically
48khz or 44.1khz.  In our application (sipXtapi - open source SIP) there was
much improvement in Jitter levels on Windows when we did this.  Once inside
our software (or outgoing from our software) we resampled using speexdsp
resampler, which is much better from a jitter perspective than relying on
the driver's resampler.  I believe we also saw some improvement on Linux,
however I think it was less of an improvement (jitter wasn't as much of a
problem on Linux).
If you're interested in ways of smoothing out jitter, you could take a look
at the sipXtapi dejitter code in our svn repository -- now over at
http://scm.sipfoundry.org/rep/sipX/main

I don't believe there is any dejitter tools in speexdsp, however I could be
wrong...

On Mon, Sep 22, 2008 at 8:55 AM, p_j_r_m <p_j_r_m at yahoo.com> wrote:
> Hi:
>
> I'm using speex to perform echo cancellation in Windows. I'm aware
of the
> problem about out of sync clocks in record and play sample rates in usual
> sound cards . In order to have an idea of how good is my echo cancelation
> working I would like to know if there is any #define thing i can pass to
> speex_echo_ctl to get the actual level of echo cancellation. If not, how
can
> i extract that value from the library?
> By the way, is any software solution for out of sync problem ? I'm
trying
> to keep input and output buffers adjusted by resampling, but it does not
> work well.
>
> Thanks
>
>
> _______________________________________________
> Speex-dev mailing list
> Speex-dev at xiph.org
> http://lists.xiph.org/mailman/listinfo/speex-dev
>
>

-- 
Keith Kyzivat

SIPez LLC.
SIP VoIP, IM and Presence Consulting
http://www.SIPez.com
tel: +1 (617) 273-4000
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