RE: [Linphone-developers] Linphone customisation

[M Walton]

Hi Simon,

Many thanks for your help so far, my soundcard plugin is now working and 
looking good.

You mentioned that you had the beginnings of VAD code in the msvolume.c, but it 
is not yet complete in the fact that it doesnt do anything with its results...

I have been looking at this source, and i am a little confused as to what 
functions do what in the setup, could you confirm if im on the right tracks?

MS_VOLUME_GET           // Log volume of current packet
MS_VOLUME_GET_LINEAR    // Linear volume of current packet
MS_VOLUME_SET_GAIN      // Increases/Decreases the volume of the current packet?
MS_VOLUME_GET_EA_STATE  //Removes any acoustice echo from the computation?
MS_VOLUME_SET_PEER      
MS_VOLUME_SET_EA_THRESHOLD //VAD Threshold
MS_VOLUME_SET_EA_SPEED     //VAD Speed
MS_VOLUME_SET_EA_FORCE     //Amplitude needed to becom of interest to the VAD 
algorithm?

My oher option is to explore a simple power threshold technique, but by looking 
at the code in msvolume, i think its using a similar equation?

Kindest regards

Billy

-----Original Message-----
From: Simon Morlat [mailto:address@hidden 
Sent: 30 November 2009 2:37 PM
To: M Walton
Cc: address@hidden
Subject: Re: [Linphone-developers] Linphone customisation

Hi Billy,

I think you need to implement a soundcard plugin in mediastreamer2; take
example over mediastreamer2/src/alsa.c or mediastreamer2/src/winsnd2.c
Basically this consists in implementing 2 MSFilter, one for reading from
your special soundcard, one for writing to it, and one MSSndCard object
representing your soundcard, that will be responsible for creating the
MSFilter when asked.
Then it should work without any modification outside.
I recommend this method over the other one of using wav files to
communicate with the pseudo-soundcard.

For VAD, in 3.1.2 there is a start of VAD code in
mediastreamer2/src/msvolume.c actually based on speex VAD. However it is
not finished (notification of the application is not implemented), and
untested.
Hope this helps,

Simon


Le vendredi 27 novembre 2009 à 10:13 +0000, M Walton a écrit :
> Hello everybody,
> 
>  
> 
> My name is Billy and i have just joined this list - sorry for a long
> first post!.  I have been given a project which could involve using
> the functionality of Linphone, and i was hoping somebody may have the
> time to give me a few pointers to help me get started.
> 
>  
> 
> My project involves interfacing some already built audio hardware to a
> SIP Client type interface.  It is based on a Blackfin platform running
> a uClinux Dist.  No video needed, just audio.  The other hardware has
> an ethernet connection (local and dedicated, not via internet so
> streaming is easier) and expects an ADPCM stream over UDP, as well as
> sending the same back.
> 
> I have identified 3 areas which i will need to make modifications:
> 
>  
> 
> 1)There is no soundcard on the hardware, i will need to catch the PCM
> output from Linphone and convert it using a library i have written
> before which will stream it onto the local LAN.  I will also have to
> pipe the return speech stream back into Linphone in a similar way.
> 
>  
> 
> 2)I will have to add some signalling between Linphone and the current
> hardware to setup/tear down the calls.
> 
>  
> 
> 3)I need to somehow provide a VAD flag so i can identify if the ADPCM
> block just converted actually has something of interest in (as the
> current audio hardware is simplex).
> 
>  
> 
> I have LinPhone (V3.0) compiled and running on Blackfin uClinux
> 2009R1.  I think i will simply modify the LinphoneC app to achieve the
> signalling part.
> 
>  
> 
> To do the custom conversions into framed ADPCM, is it best to write a
> new filter to work with the MediaStreamer? - or somehow get linphone
> to pipe the PCM data in and out of files which are shared with a
> separate conversion application? or maybe use a Pipe? any ideas here
> welcome.
> 
>  
> 
> As for the VAD, well that seems the hardest at the moment, i guess it
> should be implemented with the ADPCM conversion routines, and i am
> looking at the Speex source and wondering at the moment!
> 
>  
> 
> So if anyone could suggest a pointer or two on how to best get started
> customising with the Linphone source id be greatly appreciative.
> 
>  
> 
> Many thanks
> 
> Billy
> 
>  
> 
>  
> 
> Billy Walton
> 
> Development Engineer
> 
> Lismore Instruments Ltd
> 
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> 
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> 
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>  
> 
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> 
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> 
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