[rohc] Clarification required for CSRC List Compression

[Anil Maguluri <Anil.Maguluri at lntinfotech.com>]

Hi All, 

I have few queries regarding the CSRC List Compression. 

Please clarify me whether my understanding is right or wrong. 

Scenario1: The reference list is set b/w compressor and decompressor.
After that compressor received RTP packet with the same CSRC list [list
is not changed]. 
Q1. How compressor will inform to decompressor about the CSRC List?

As per my understanding, Compressor will inform [send Encoding Type 0/1/2/3]
to decompressor only when the list changes. In the scenario1, compressor
will not send any information about the CSRC list to the decompressor.
Decompressor will reconstruct the packet using the ref_list. 

Scenario2: The reference list is set b/w compressor and decompressor.
After that compressor received rtp packet with CC value is zero. 
Q: How will compressor will inform to decompressor about the CSRC List?

As per my understanding, Compressor will always compare with ref_list to
create the compressed packet. compressor will generate new Gen_ID and it
compare with the ref_list to create compressed packet. In the above scenario,
compressor will send removal scheme only using the removal bitmask setting
the all 1's [based on the ref_list items]. is it right? Otherwise decompressor
will reconstruct the packet using the ref_list. 

Scenario3: The reference list is set b/w compressor and decompressor.
Compressor moved to IR->FO state. Now compressor received the RTP packet
with the same CSRC list [List is not changed]. Compressor selected IR-DYN
packet based on the state and mode. 
Q: What value to encode in CC field and Generic CSRC List field? 

Thanks & Regards, 
Anil Kumar Maguluri 

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