rohc team mailing list archive

[Didier Barvaux <didier@xxxxxxxxxxx>]

Hi,

> I have a general question about the no compression profile (0).
> 
> How does the compressor decide on using it? should there be some kind
> of indication from upper layers telling the compressor to use profile
> 0 to compress the packet? or the other profiles must be deactivated
> on the channel before sending the packet, so the compressor finds
> only profile 0 to use?

There are 2 possibilities in the ROHC library:
 - If no other compression profile matches the packet, then the
   uncompressed profile is selected.
 - If the compression of the packet fails with the selected compression
   profile, then the compressor tries again with the uncompressed
   profile.


> I know that some packets that are rarely appear on the link, get sent
> with profile 0 to save memory resources needed for a new context,

The ROHC library does not handle such case.


> but my question is for normal IP packets, if i want to test rohc
> without doing any compression, only CRC in IR packets and CID octet
> (if cid != 0) and the optional feedback to trigger transition to
> bidirectional mode,...etc.

If you want to use only the uncompressed profile, then enable only the
uncompressed profile with the rohc_activate_profile() function.

See the API description:
http://www.tech.viveris.com/docs/rohc/group__rohc__comp.html#g1a444eb91681521f726712a60a4df867

See an example here:
http://bazaar.launchpad.net/~didier-barvaux/rohc/main/annotate/head:/examples/simple_rohc_program.c#L102


Regards,
Didier Barvaux

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