C_TRANS and D_TRANS

Asked by regulararmy on 2014-01-16

Hello Didier,
          In the RFC3095 or RFC3843, it mentions the mode transitions among the U_Mode/O_Mode/R_Mode, there are two parameters C_TRANS and D_TRANS in the procedure; However, I can not find variables corresponding to C_TRANS and D_TRANS in your lib codes.why? Thanks.
          In addition, in the second step of mode transtion procedure in the RFC protocol documents, IR/IR_DYN/UOR-2(SN,U/O/R) is sent from compressor to decompressor, However, IR/IR_DYN packet format do not have the 'Mode' field ,and the UOR-2 packet format has the mode field only when it consists of 'RTP header flags and fields' in the Extension 3, so, when it is not RTP profile currently, how can the compressor send mode informations to the decompressor?Thanks.

Regards,
cxs

Question information

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Status:
Solved
For:
rohc Edit question
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Solved by:
Didier Barvaux
Solved:
2014-01-20
Last query:
2014-01-20
Last reply:
2014-01-19
regulararmy (regulararmy) said : #1

Now I know the Extension 3 fomat has the 'Mode' field in it whenever, not only the RTP profile. However, the IR/IR_DRN does not has the field, does it?

Hello,

The ROHC library does not support that the ROHC compressor changes the operational mode by itself. The ROHC library only support that the ROHC decompressor asks the ROHC compressor to change the operational mode (through a feedback packet). So, the C_TRANS and D_TRANS parameters are not fully implemented. I created a blueprint for this feature (https://blueprints.launchpad.net/rohc/+spec/mode-transitions) for release 1.8.0.

About the packet formats, the IR and IR-DYN packets of the RTP profile got a Mode field in the RTP dynamic part. See https://tools.ietf.org/html/rfc3095#section-5.7.7.6

Regards,
Didier

regulararmy (regulararmy) said : #3

Thanks Didier Barvaux, that solved my question.