[Linphone-users] adding G726-40,32,24,16 dynamic PT codecs to oRTP

[Dimitris Tsaimos]

Hello everybody,

I am currently trying to develop an RTP application running in the 
Coyote development board. For voice encoding and decoding I am using the 
Intel DSR2.5 software. I also use oRTP to send and receive RTP packets.

What I would like to do is to embody support for the G726 codec flavors 
to oRTP. I have already edited the files payloadtype.h and avprofile.c 
as follows

avprofile.c:

PayloadType payload_type_g726_40={
   TYPE( PAYLOAD_AUDIO_CONTINUOUS),
   CLOCK_RATE(8000),
   BITS_PER_SAMPLE(5),
   ZERO_PATTERN(NULL),
   PATTERN_LENGTH(0),
   NORMAL_BITRATE(40000),
   MIME_TYPE ("G726-40")
};

PayloadType payload_type_g726_32={
   TYPE( PAYLOAD_AUDIO_CONTINUOUS),
   CLOCK_RATE(8000),
   BITS_PER_SAMPLE(4),
   ZERO_PATTERN(NULL),
   PATTERN_LENGTH(0),
   NORMAL_BITRATE(32000),
   MIME_TYPE ("G726-32")
};

PayloadType payload_type_g726_24={
   TYPE( PAYLOAD_AUDIO_CONTINUOUS),
   CLOCK_RATE(8000),
   BITS_PER_SAMPLE(3),
   ZERO_PATTERN(NULL),
   PATTERN_LENGTH(0),
   NORMAL_BITRATE(24000),
   MIME_TYPE ("G726-24")
};

PayloadType payload_type_g726_16={
   TYPE( PAYLOAD_AUDIO_CONTINUOUS),
   CLOCK_RATE(16000),
   BITS_PER_SAMPLE(2),
   ZERO_PATTERN(NULL),
   PATTERN_LENGTH(0),
   NORMAL_BITRATE(16000),
   MIME_TYPE ("G726-16")

payloadtype.h

extern PayloadType payload_type_g726_40;
extern PayloadType payload_type_g726_32;
extern PayloadType payload_type_g726_24;
extern PayloadType payload_type_g726_16;

When I try to set up a conversation with the SIPURA ATA using any of the 
above codecs, I get annoying noise.... - which could be due to further 
modifications needed to the oRTP lib or some internal imlementation 
error, that is what I am trying to find out. However, my code works just 
fine with ALL static PT codecs -G711, G729a.G723. Are there any further 
modifications that should be applied to oRTP to support the 
aforementioned codecs?

Additionally, the RTP payload type of theses codecs is determined by  
the call stack and should be decided on a per call basis. Could anybody 
tell me - preferrably using an example - what are the functions I should 
call in order to perform such a task?

Any help would be greatly appreciated.

Regards,
Dimitris

--
Dipl-Ing Dimitris H. Tsaimos
Senior Engineer
Systems Design Group
Keletron Ltd                    Tel:     +30-2310-947979
49 D.Glinou street              Fax:     +30-2310-947386
543 52 Thessaloniki             e-mail:  address@hidden