Re: [Linphone-developers] Newbie question

[Kosta Welke]

Asim Jamshed wrote:
> I wish to modify the linphone source code slightly... Instead of
> receiving calls, I wish to morph it into an answering machine... so
> that whenever someone calls my linphone, its audio clip is saved in a
> file. 

Maybe you also want to play a message before recording? :)

> Since I am entirely new to the OSS architecture, 

linphone is sound-architecture-independent :)

> I need guidance
> to understand the entire architecture of linphone. Thanx,

You have to decide if you want to save the call as wave file, in the 
codec format used by RTP (GSM, ulaw, speex, ...) or in a different 
format (ogg, mp3).

Basically, instead of writing to the sound card, you need to write to a 
file. linphone has a struct called MSFilter. Multiple filters are used 
to build a filter chain. Each filter does one step of the en/de-coding 
process, like read from a soundcard, write to a soundcard, encode to 
codec, decode to codec, etc. To see an example, use the console client 
linphonec, it displays the filter chains it builts.

MSFilter are a bit hard to understand in the beginnning. If you are 
familiar with C++, think of pure virtual member functions. Only, as it 
is C, not C++, its done using function pointers in the init function 
(which basically takes the role of the constructor)
The process functions do the actual work.

What you would need to do is write a new MSFilter that saves to/reads 
from a file instead of the soundcard.

HTH,
Kosta