Re: [GnomeMeeting-list] Enforcing half-duplex?

[Damien Sandras <dsandras seconix com>]

Hi Stefan,

We have to rediscuss that after 1.00 has been released. Craig will help
us in that respect.


Le sam 07/02/2004 à 13:11, Stefan Bruens a écrit :
> Am Samstag, 7. Februar 2004 12:45 schrieb Damien Sandras:
> > Le sam 07/02/2004 à 00:12, Conrad Beckert a écrit :
> > > Pardon for jumping in ;-)
> > >
> > > >>Something that mutes the local speakers if the level
> > >
> > > on the mic is above a given level with respect to
> > > what's received from peer and mutes the mic
> > > otherwise?<<
> > > It should be possible to cancel the echos: As the PC
> > > "knows" what it sent to the speakers it should be able
> > > to subtract exactly that from the stream it recieves
> > > from the microphone. (delayed a couple of microseconds
> > > - the time the sound travels from the speakers to the
> > > microphone + signal delay in the sound card)
> > >
> > > Doesn't Gnomemeeting, or OpenH323 rather, already have
> > > such a feature? I have no problems with feedback
> > > interference.
> >
> > It is foreseen after 1.00 to have echo cancellation. The problem with
> > that kind of algorithm is that it consumes a lot of CPU if you want high
> > quality. But we have plans about that, yes.
> 
> I have some code laying on my harddisk, it is doing a 256 tap echo 
> cancellation with double talk detection, the result are quite good. The code 
> is not optimized nor really clean, but it does the calculation (8kHz, 16bit) 
> on a 700MHz Duron at approx. 10% cpu usage.
> 
> At the moment, the code is not ready for real use, the test program is only 
> working on prerecorded raw audio, and I have only run minimal tests. I have 
> uploaded some waveform plots to  
> http://www.kawo1.rwth-aachen.de/~lurchi/echo/index.html .
> 
> Problems:
> Code cleanup needed
> How to incorporate into pwlib
> More testing needed
> Do some postprocessing?
> Patent infringements? (Don't think so, but not sure)
> and last: I am busy at the moment, till 26th of Feb. ...
> 
> 
> Greetings,
> 
> Stefan
-- 
 _      Damien Sandras
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