Re: [Linphone-developers] Echo Canceler

[Simon MORLAT]

Thanks a lot for all !
In fact I have the secret hope to soon cleanup the mediastreamer to be 
able to handle properly those kind of complex chains...
Once this is done, your echocanceler will work perfectly !
Simon

Charles Eidsness wrote:

> I had a chance to clean up some of these error messages. If anyone's 
> interested I've uploaded a new patch here:
>
> http://members.rogers.com/charles.eidsness/linphone-0.12.2.ec.patch
>
> The two "opening soundcard" messages were because the osswrite filter 
> was on the process chain twice. I have a not very elegant solution 
> tacked on to the end of that patch, it makes a few changes to ms.c.
>
> All of the error messages during call termination were a result of me 
> forgetting to close some of the links properly in my original patch, 
> this is fixed.
>
> I've also found a new issue which only appears during an incoming 
> call. I get a lot of ossread errors because the fifo between the 
> ossread filter and the echo canceler filter is full. This is because 
> the other fifo input to the echo canceler filter is empty. The process 
> chain runs the filter until one input fifo is below the threshold, not 
> both. The puzzling thing is that these error messages don't appear 
> during an outgoing call. I'm guessing it has something to do with the 
> initial filter process order.
>
> I guess implementing a multi-input / multi-output filter will take a 
> little more work but I think this is close.
>
> Cheers,
> Charles
>
> Charles Eidsness wrote:
>
> > Simon,
> >
> > Thanks, and thank you for this excellent software. I particularly 
> > like the mediastremaer framework. It's so simple and straight-forward 
> > it didn't take me very long to figure out how to implement my own 
> > filter.
> >
> > I had no "show-stopper" issues with a 2 input / 2 output filter but I 
> > do get some strange errors logged to the terminal that I haven't had 
> > time to take a look at. These errors don't seem to effect the call at 
> > all.
> >
> > I get a bunch of these:
> >
> > Debug: sleeping function called from invalid context at mm/slab.c:1989
> > in_atomic():1, irqs_disabled():1 .... followed by a long call trace
> >
> > But this is probably just a result of the way I have my kernel / 
> > system configured.
> >
> > I get two "Opening soundcard" messages, i.e.:
> >
> > Message:ms_filter_add_link: OssRead,0 -> EC,1
> > Message:ms_filter_add_link: EC,1 -> GSMEncoder,0
> > Message:ms_filter_add_link: GSMEncoder,0 -> RTPSend,0
> > Message:ms_filter_add_link: RTPRecv,0 -> GSMDecoder,0
> > Message:ms_filter_add_link: GSMDecoder,0 -> EC,0
> > Message:ms_filter_add_link: EC,0 -> OssWrite,0
> > Message:Opening sound card in capture mode with 
> > stereo=0,rate=8000,bits=16
> > Message:dsp blocksize is 512.
> > Message:Opening sound card in playback mode with 
> > stereo=0,rate=8000,bits=16
> > Message:Opening sound card in playback mode with 
> > stereo=0,rate=8000,bits=16
> >
> > And it doesn't terminate the call very cleanly. I get a bunch of these:
> >
> > msosswrite.c:148- assertionw->sndcard!=NULLfailed
> > msfilter.c:414- assertionf->finputs==0failed
> > msfilter.c:415- assertionf->foutputs==0failed
> > msfilter.c:414- assertionf->finputs==0failed
> > msfilter.c:414- assertionf->finputs==0failed
> > msfilter.c:415- assertionf->foutputs==0failed
> >
> > As mentioned in my previous email I'm using a fairly unique system. 
> > I'm running on an embedded MIPS processor using uclibc and using an 
> > ALSA driver I wrote myself so these errors may not appear on a 
> > "normal" system, or there may be different errors.
> >
> > If you add a checkbox for this echo canceler make sure you mention 
> > it's experimental. :)
> >
> > I think the algorithm itself could still use some tweaking too. It 
> > will behave in a different manner depending on the level of 
> > background noise and so far I've only been testing it with a fixed 
> > level. I'll try to improve it as I get more time but if there's 
> > anyone out there that is interested in signal processing and wants to 
> > take a look at it that would be really cool.
> >
> > Cheers,
> > Charles
> >
> > Simon MORLAT wrote:
> >
> > > Hello,
> > >
> > > I've just had a look on your excellent work, thank you very much.
> > > I saw that you implemented a 2-input 2-output MSFilter to achieve 
> > > this, this is actually exactly the right way... but I didn't think 
> > > that the mediastreamer was able to nearly correctly handle those 
> > > kind of complex graphs... Actually the scheduling algorithm I've 
> > > implemented was first designed to run simple linear graphs. You 
> > > haven't experienced strange things about that ?
> > > Anyway as it works I will integrate it into linphone and add 
> > > checkbutton to enable/disable it. It may take some time, because the 
> > > goal for now is to stabilize the 1.0.0 release first.
> > >
> > > Simon
> > >
> > >
> > > Charles Eidsness wrote:
> > >
> > > > Hi All,
> > > >
> > > > I've been working on an acoustic echo canceler for Linphone. I have 
> > > > something that kind-of works for me and thought I'd post it in case 
> > > > there's someone else out there interested. I think it just needs a 
> > > > little more tuning, I hope to have it functional someday.
> > > >
> > > > I've been using Linphone 0.12.1, and am using uClibc on an embedded 
> > > > MIPS processor so there's a chance it may not work on another 
> > > > platform. I've been trying to keep everything as fixed-point math 
> > > > since there's no FPU on my processor but I did implement a couple 
> > > > filters as floating point. (I'm using soft-float from gcc compiler) 
> > > > Also, I borrowed liberally from the mark2 echo canceler which is 
> > > > part of the Zaptel package for Asterisk so you can look at it as 
> > > > well if you're super-keen.
> > > >
> > > > I split my changes / additions into three patches to make them 
> > > > easier to take a quick look at:
> > > >
> > > > members.rogers.com/charles.eidsness/linphone.0.12.1-ec.source.patch
> > > > -- adds ec.c and ec.h to the mediastreamer
> > > >
> > > > members.rogers.com/charles.eidsness/linphone.0.12.1-ec.msEC.patch
> > > > -- adds msEC.c, msEC.h and test_ec to the mediastreamer
> > > >
> > > > members.rogers.com/charles.eidsness/linphone.0.12.1-ec.setup.patch
> > > > -- edits the mediastreamers Makefile.am, audiostream.c and 
> > > > mediastream.h to add a echo canceler filter block in the audio stream
> > > >
> > > > members.rogers.com/charles.eidsness/linphone.0.12.1-ec.patch
> > > > -- all three patches in one file
> > > >
> > > > Cheers,
> > > > Charles
> > > >
> > > >
> > > > _______________________________________________
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> >
> >
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