Clarification sought for RTP CSRC list compression [RohC v1]

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Dear all,

Would appreciate if someone can clarify the following doubt.

Consider an RTP flow with all packets having one CSRC element.

Case 1:
The compressor creates a gen_id for the list and starts enocoding these
packets in ET=0 packet types along with gen_id.
At some of point of time it decides to use this gen_id as ref_id and encodes
the packet without the CSRC info(say U0 packet)
and expects the decompressor to use the ref_id to recreate the CSRC element.

Case 2.
The compressor creates a gen_id for the list and starts enocoding these
packets in ET=0 packet types along with gen_id.
At some of time before it receives a packet without any CSRC element and
thus enocodes it using a packet type without CSRC info (say U0).

How does the decompressor differentiate between the two cases. For case 1,
the decompressor should refer to its ref_id and create CSRC element
whereas for case 2 it should not.How can the decompressor decide if the
compressed packet it received is encoded using a reference list or not.

Additionally, how does the compressor informs the decompressor not to use
the ref_id any more.

Regards,
Vivek

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<div>Dear all,</div><div><br></div><div>Would appreciate if someone can cla=
rify the following doubt.</div><div><br></div><div>Consider an RTP flow wit=
h all packets having one CSRC element.</div><div><br></div><div>Case 1:</di=
v>
<div>The compressor creates a gen_id for the list and starts enocoding thes=
e packets in ET=3D0 packet types along with gen_id.</div><div>At some of po=
int of time it decides to use this gen_id as ref_id and encodes the packet =
without the CSRC info(say U0 packet)=A0</div>
<div>and expects the decompressor to use the ref_id to recreate the CSRC el=
ement.</div><div><br></div><div>Case 2.=A0</div><div>The compressor creates=
 a gen_id for the list and starts enocoding these packets in ET=3D0 packet =
types along with gen_id.</div>
<div>At some of time before it receives a packet without any CSRC element a=
nd thus enocodes it using a packet type without CSRC info (say U0).</div><d=
iv><br></div><div>How does the decompressor differentiate between the two c=
ases. For case 1, the decompressor should refer to its ref_id and create CS=
RC element</div>
<div>whereas for case 2 it should not.How can the decompressor decide if th=
e compressed packet it received is encoded using a reference list or not.</=
div><div><br></div><div>Additionally, how does the compressor informs the d=
ecompressor not to use the ref_id any more.</div>
<div><br></div><div>Regards,</div><div>Vivek=A0</div><div><br></div>

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