Subject: [rohc] Clarification sought for RTP CSRC list compression [RohC v1]

From: Vivek Soni <[email-masked]>
Date: Mon, 25 Apr 2011 19:11:40 +0900

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