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[Didier Barvaux <didier@xxxxxxxxxxx>]

Hello,

>             When I send rtp packets using the rohctunnel application,
> I get the following message during decompression and the decompressor
> uses the udp profile. Can anyone shed a bit of light on this please?
> 
> [rohc_comp.c:986 c_get_profile_from_packet()] skip profile 'RTP /
> Compressor' (0x0001) because UDP destination port is not reserved for
> profile

The recognition of RTP streams within all UDP streams is quite basic in
the current versions of the ROHC library.

The RTP standard does not define a UDP port for RTP streams, so it is
quite difficult to recognize a RTP stream. The current mechanism is
based on a predefined list of UDP ports dedicated to the RTP streams.

If the compressor receives one UDP packet, it looks after its port
number. If the port number is within the static list of ports dedicated
to RTP, then the UDP packet is compressed with the RTP profile.
Otherwise the UDP packet is compressed with the UDP profile.

The static list of UDP ports for RTP may be found in the source code.
You need to rebuild the library to change the list. In the trunk, the
list is defined in the src/comp/c_rtp.c file:
http://bazaar.launchpad.net/~didier-barvaux/rohc/main/annotate/head:/src/comp/c_rtp.c#L38

This is not convenient at all. The mechanism should probably be changed
in the future.

Regards,
Didier Barvaux

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