c_get_profile_from_id

Hello,

You don't need to modify the source code of the library to detect RTP streams. You have two ways to do it:

1/ static list of UDP ports

You give the ROHC compressor a list of UDP ports that are dedicated to RTP streams. See the API documentation:

http://rohc-lib.org/support/documentation/API/rohc-doc-1.6.1/group__rohc__comp.html#ga60547b56cea992e4967a99391fcd6489

http://rohc-lib.org/support/documentation/API/rohc-doc-1.6.1/group__rohc__comp.html#gae4007c48b1aaed847df86bf42f0b0e96

http://rohc-lib.org/support/documentation/API/rohc-doc-1.6.1/group__rohc__comp.html#ga4c2adababf10a9c65c9f8ec892217971

And an example:

http://bazaar.launchpad.net/~didier-barvaux/rohc/1.6.x/view/head:/test/functional/rtp_detection/test_rtp_ports.c

2/ callback function

Use the rohc_comp_set_rtp_detection_cb() function to give the ROHC compressor a function that it will call for every UDP packet. You have to write your own function. The function receives the IP headers, UDP header, and UDP payload as argument. The function returns true if packet is part if a RTP stream, false if it doesn't.

See http://rohc-lib.org/support/documentation/API/rohc-doc-1.6.1/group__rohc__comp.html#gae46d8370a4dbdb9153da8e89899b5596 for the API documentation.

See the example here http://bazaar.launchpad.net/~didier-barvaux/rohc/1.6.x/view/head:/test/functional/rtp_detection/test_rtp_callback.c

Regards,
Didier

Hi Didier,

I would like to use the second method since I have too many UDP ports. In your example,

if(!rohc_comp_set_rtp_detection_cb(comp, callback_detect, NULL))
  {
   fprintf(stderr, "failed to set RTP detection callback\n");
   goto destroy_comp;
  }

  expected_profile = ROHC_PROFILE_RTP;

Suppose that I have a good callback_detect(). The program will execute "expected_profile = ROHC_PROFILE_RTP; "

My question is how I can use "expected_profile". I saw no use of it in your compressing example:
ret = rohc_compress2(comp, ip_packet, ip_size,
                      rohc_packet, MAX_ROHC_SIZE, &rohc_size);

How can the compressor know it is the RTP packet and compress it accordingly?

Thanks!

Hello,

The 'expected_profile' is defined for the purpose of the test only. It is not used by the ROHC library itself. I created an example for port-based detection and callback-based detection of RTP packets. It should help you understand how it works.

http://bazaar.launchpad.net/~didier-barvaux/rohc/main/view/head:/examples/rtp_detection.c

The example above will now be included in the library documentation.

Regards,
Didier