[xrblock] Fw: Comments on draft-ietf-xrblock-rtcp-xr-synchronization-00

Qin Wu <bill.wu@huawei.com> Tue, 23 October 2012 02:29 UTC

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From: Qin Wu <bill.wu@huawei.com>
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Date: Tue, 23 Oct 2012 10:29:24 +0800
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Subject: [xrblock] Fw: Comments on draft-ietf-xrblock-rtcp-xr-synchronization-00
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Please see comments inline.

----- Original Message ----- 
From: Huangyihong (Rachel) 
To: xrblock@ietf.org 
Sent: Thursday, October 18, 2012 11:30 AM
Subject: [xrblock] Comments on draft-ietf-xrblock-rtcp-xr-synchronization-00

Hi folks,


I have 2 comments for draft-ietf-xrblock-rtcp-xr-synchronization:


1.       In RTP flows synchronization offset metric block, only one SSRC set to the SSRC of the reference RTP stream has been specified. IMO,  the SSRC of the reporting stream should be also required. 

[Qin]: Are you saying the synchronization offset is applied to two streams and used to measure the time difference between two stream, so for reporting stream, how to choose the reference stream?

2.       Synchronization offset is a 64-bit unsigned fixed-point number. No indication shows which stream, the reporting stream or the reference stream,  is lag behind. So I propose to split one bit from "Reserved" field to indicate the offset direction.

[Qin]: What do you mean offset direction? Are you saying the value of offset can be either less than zero or greater than zero? However in the current text, the synchronization offset is unsigned value or positive value.

       I am thinking if we can choose one slow stream as reference stream, in that case, the offset value is always a positive value.


Best Regards!




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