[Linphone-developers] Linphone customisation

[M Walton]

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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