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Re: [Question #229419]: What protocol number should be for RTP header compression

 

Question #229419 on rohc changed:
https://answers.launchpad.net/rohc/+question/229419

    Status: Open => Answered

Didier Barvaux proposed the following answer:
Wei,

There were several mistakes:
 1/ wrong IP Total Length (Host Byte Order instead of Network Byte Order),
 2/ wrong IP checksum (you altered the IP header but didn't update the checksum),
 3/ wrong UDP port (I changed for 1234 for UDP to be recognized as RTP).

The ROHC compressor didn't use the RTP profile because of problems 1 and
3. The ROHC decompressor failed to decompress some ROHC packets because
of problem 3.

Once the problems were fixed, I got the following ROHC packet lengths:
54, 64, 57, 57, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19
(the 2nd packet is larger than the 1st because of 7 bytes of feedback data)

Please find the changes in the code here: http://pastebin.com/bVvqvjhd

Regards,
Didier

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