Re: [xrblock] Comments on draft-ietf-xrblock-rtcp-xr-synchronization-00
Qin Wu <bill.wu@huawei.com> Thu, 18 October 2012 02:48 UTC
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From: Qin Wu <bill.wu@huawei.com>
To: "Claire Bi(jiayu)" <bijy@sttri.com.cn>, xrblock <xrblock@ietf.org>
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Date: Thu, 18 Oct 2012 10:47:46 +0800
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Subject: Re: [xrblock] Comments on draft-ietf-xrblock-rtcp-xr-synchronization-00
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Hi,Claire: Thank for your reivew to draft-ietf-xrblock-rtcp-xr-synchronization-00. Below is my reply inline. Regards! -Qin ----- Original Message ----- From: Claire Bi(jiayu) To: xrblock Sent: Thursday, October 18, 2012 9:19 AM Subject: [xrblock] Comments on draft-ietf-xrblock-rtcp-xr-synchronization-00 Hi, I was asked to review draft-ietf-xrblock-rtcp-xr-synchronization-00 and have the following several comments. 1. Section 2.1, Synchronization Offset Is Synchronization Offset a absolute value or relative value? Is Synchronizztion Offset delay variance or Delay Variation? [Qin]: Our intention is to define Synchronization Offset as relative value. Synchronization offset is actually the time difference between two media streams that need to be synchronized. So I like to propose the following change to the defintion of Synchronization Offset in the terminology section. OLD TEXT: " Synchronization Offset: The absolute delay variance of the measured RTP stream relative to the reference RTP stream in the multimedia session. " NEW TEXT: " Synchronization Offset: Synchronization between two media streams must be maintained to ensure satisfactory QoE. Two media streams can be of the same media type belonging to one RTP session or in different media types belonging to one multimedia session. The Synchronization Offset is the relative time difference of the two media streams that need to be synchronized. " 2. Section 3, last Paragraph said: " For example, one audio stream and one video stream belong to the same session and audio stream are transmitted lag behind video stream for multiple tens of milliseconds. The RTP Flows Synchronization Offset block can be used to report such synchronization offset between video stream and audio stream " Would you like to provide a reference to this example? [Qin]: On relevant reference in my mind is BBF Forum document TR-126. I will put it into the next version. 3. Section 4.2 s/Statistics Summary Report Block/RTP Flows Initial Synchronization Delay Report Block [Qin]: Good catch, thanks. 4. Section4.2 Definition of Initial Synchronization Delay It is not clear how to use in-band mapping of RTP and NTP-format timestamps to calculate the intial Synchronization Delay, it is better to add text to clarify this. [Qin]: Okay, I propose the following change to the definition of Initial Synchronization Delay. OLD TEXT: " Initial Synchronization Delay: 32 bits The average delay, expressed in units of 1/65536 seconds, from the RTCP packets received on all of the components RTP sessions to the beginning of session [RFC6051]. The value is calculated based on the information contained in RTCP SR packets or the in-band mapping of RTP and NTP-format timestamps [RFC6051]. If there is no packet loss, the initial synchronization delay is expected to be equal to the average time taken to receive the first RTCP packet in the RTP session with the longest RTCP reporting interval. " NEW TEXT: " The average delay, expressed in units of 1/65536 seconds, from the RTCP packets received on all of the components RTP sessions to the beginning of session [RFC6051]. The value is calculated based on received RTCP SR packets or the RTP header extension containing in-band mapping of RTP and NTP-format timestamps [RFC6051]. If there is no packet loss, the initial synchronization delay is expected to be equal to the average time taken to receive the first RTCP packet in the RTP session with the longest RTCP reporting interval or the average time taken to receive the first RTP header extension containing in-band mapping of RTP and NTP-format timestamps. " Claire ------------------------------------------------------------------------------ _______________________________________________ xrblock mailing list xrblock@ietf.org https://www.ietf.org/mailman/listinfo/xrblock
- [xrblock] Comments on draft-ietf-xrblock-rtcp-xr-… Claire Bi(jiayu)
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Qin Wu
- [xrblock] Comments on draft-ietf-xrblock-rtcp-xr-… Huangyihong (Rachel)
- [xrblock] Fw: Comments on draft-ietf-xrblock-rtcp… Qin Wu
- Re: [xrblock] Fw: Comments on draft-ietf-xrblock-… Huangyihong (Rachel)
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Colin Perkins
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Huangyihong (Rachel)
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Colin Perkins
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Huangyihong (Rachel)
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Hitoshi Asaeda
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Kevin Gross
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Huangyihong (Rachel)
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Colin Perkins
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Kevin Gross
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Kevin Gross
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Huangyihong (Rachel)
- Re: [xrblock] Comments on draft-ietf-xrblock-rtcp… Huangyihong (Rachel)
- [xrblock] 答复: Comments on draft-ietf-xrblock-rtcp… Qin Wu
- Re: [xrblock] 答复: Comments on draft-ietf-xrblock-… Kevin Gross
- [xrblock] 答复: 答复: Comments on draft-ietf-xrblock-… Huangyihong (Rachel)
- [xrblock] 答复: 答复: Comments on draft-ietf-xrblock-… Huangyihong (Rachel)