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[Didier Barvaux <question230140@xxxxxxxxxxxxxxxxxxxxx>]

Question #230140 on rohc changed:
https://answers.launchpad.net/rohc/+question/230140

    Status: Open => Answered

Didier Barvaux proposed the following answer:
Hello,

>  Firstly,as for the function d_operation_mode_feedback(...) in rohc_decomp.c,
> there is a switch(mode) in it,the first case is U_MODE, which does not need
> feedback, however, the statement “break;” is removed by annotation //,is it a
bug?

The decompressor starts in U-mode. When it decompresses the first
packets, if it is associated with a compressor, it will always try to
send a positive ROHC feedback with mode O-mode to the compressor. The
U-mode -> O-mode transition is achieved this way. If you don't want the
decompressor to ask compressor for O-mode, don't associate it with a
local compressor.

> what is more ,the feedback for R_MODE is not implemented yet, can I use
> your library in my production realization

This question was already asked several times on the mailing list.
Please check list archives before asking questions. R-mode is not
implemented at all in the ROHC library. The library can be used in
production (in U- and O-modes). In fact, I got reports that the library
is currently used in production without any problem: no stability
problem & great performances :)

> Secondly,I wonder if the compression or decompression logic of your
> library codes is as follows: the comp and decomp entity is initialized to
> U_mode ,then, the comp and decomp entity transiton to O_MODE or
> R_MODE or back to U_MODE automatically and adaptively ,I do not need
> to think them over?

Compressor/decompressor start in U-mode. If a feedback channel is
defined (= decompressor associated with another local compressor), it
will go to O-mode. R-mode is not implemented. There is no O-mode ->
U-mode transition. All of those transitions are automated, you don't
need to do anything. Just configure or do not configure a feedback
channel for your decompressors.

Regards,
Didier

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