[AVT] [Fwd: Re: Review requested: draft-ietf-avt-rtp-toffset-04.txt]
"Tom-PT Taylor" <taylor@nortel.com> Thu, 08 February 2007 21:49 UTC
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Date: Thu, 08 Feb 2007 16:49:03 -0500
From: Tom-PT Taylor <taylor@nortel.com>
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Subject: [AVT] [Fwd: Re: Review requested: draft-ietf-avt-rtp-toffset-04.txt]
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Qiaobing was asked as a member of the AVT Review Team to comment on the toffset draft. I am assuming Qiaobing's consent to publish this to the list. There was some behind-the scenes discussion of these points that I will also forward. From now on, we will ensure a more efficient procedure by asking the review team to publish directly to the authors and the list. Many thanks for your review, Qiaobing. Qiaobing Xie wrote: > Tom, > > Here are my comments on the draft: > > 1. I agree with the use case analysis in the draft and agree in general > this may be a useful extension. > > 2. I would like to see a more crisp definition of the "transmission > timestamp" - what is it? Is it the time instance the first (or the last) > octet of the packet is put on the wire by the physical interface at the > RTP sender? Or is it the time instance the sending RTP stack passes the > fully assembled packet into the out-going buffer? Or, is it the time > instance the last media octet in the packet was assembled at the RTP > stack? and so on. > > 3. The following statement in the draft: > > "In the RTP specification [RFC3550] it is implied that packets are > transmitted essentially in accordance with their RTP timestamps." > > is a little misleading since RFC3550 only says: > > "The timestamp reflects the sampling instant of the first octet in > the RTP data packet." > > I'd therefore suggest to say something like: "RFC 3550 does not specify > a transmission timestamp." > > 4. The sentence: > > "When added to the RTP timestamp of the packet, it represents the > "effective" RTP transmission time of the packet, on the RTP > timescale." > > seems to say that > > Adjusted RTP timestamp = RTP timestamp in RTP header + > transmission offset > > If so, it probably is helpful to spell this out clearly. > > 5. If my understanding above (point 4) is correct, then I am confused > about the following statement: > > "The sign of the offset value depends greatly on the choice of the > initial mapping of RTP to NTP times. In general, without scanning a > stream entirely it is not possible to ensure that this mapping would > keep all the offsets positive; therefore this specification allows > negative values." > > Some more explanation would help. > > 6. In section 4, it would help if more detail can be given on how to > "indicate the actual network jitter, excluding the source-introduced > jitter". An example calculation would help too. > > regards, > -Qiaobing > _______________________________________________ Audio/Video Transport Working Group avt@ietf.org https://www1.ietf.org/mailman/listinfo/avt
- [AVT] [Fwd: Re: Review requested: draft-ietf-avt-… Tom-PT Taylor
- [AVT] [Fwd: Re: Review requested: draft-ietf-avt-… Tom-PT Taylor