Re: [AVT] Q for 3984bis-06

[Ye-Kui Wang <yekuiwang at huawei.com>]

Yes, please go ahead. 

BR,YK 

> -----Original Message-----
> From: Tom Taylor [mailto:tom.taylor at rogers.com] 
> Sent: Tuesday, May 12, 2009 3:58 AM
> To: Ye-Kui Wang
> Cc: 'Ali C. Begen (abegen)'; avt at ietf.org; ron.even.tlv at gmail.com
> Subject: Re: [AVT] Q for 3984bis-06
> 
> I was waiting for the discussion of level upgrade to settle. 
> Should I issue a summary of what I have seen so far?
> 
> Ye-Kui Wang wrote:
> > Thanks Ali. This is an intact inheritance from RFC 3984. 
> I'd agree to 
> > remove the note in the next submission.
> > 
> > BTW, AVT Chairs, what is the plan on progressing this and 
> the SVC drafts?
> > 
> > BR, YK
> > 
> >> -----Original Message-----
> >> From: avt-bounces at ietf.org [mailto:avt-bounces at ietf.org] 
> On Behalf Of 
> >> Ali C. Begen (abegen)
> >> Sent: Monday, May 11, 2009 5:08 PM
> >> To: avt at ietf.org
> >> Subject: [AVT] Q for 3984bis-06
> >>
> >> Page 12 says:
> >>
> >>          Informative note: Because H.264 allows the 
> decoding order to 
> >>          be different from the display order, values of RTP 
> >> timestamps
> >>          may not be monotonically non-decreasing as a 
> function of RTP 
> >>          sequence numbers.  Furthermore, the value for 
> inter-arrival
> >>
> >> This is not something specific for H.264 content. It applies to 
> >> almost all codecs. A rewording may be beneficial IMO.
> >>
> >>          jitter reported in the RTCP reports may not be a 
> trustworthy 
> >>          indication of the network performance, as the calculation 
> >>          rules for inter-arrival jitter (section 6.4.1 of 
> RFC 3550) 
> >>          assume that the RTP timestamp of a packet is directly 
> >>          proportional to its transmission time.
> >>
> >> What does it mean that RTP timestamp is proportional to its 
> >> transmission time? By "transmission time" do you mean the 
> instant the 
> >> packet was sent? By definition, timestamp reflects the sampling 
> >> instant of the first octet in the RTP packet. The packets 
> belong to a 
> >> single video frame will most likely have the same 
> timestamp. But that 
> >> does not mean that they will be transmitted at the same time.
> >>
> >> RFC 3550 has a simple rule here and says this rule must be 
> followed. 
> >> The packets are considered in the order they arrive, not based on 
> >> their seqnums in the jitter calculation.
> >> And the parameters needed to compute the interarrival jitter are 
> >> clock rate, timestamp and arrival-time timestamp.
> >>
> >> I suggest a revision for this informative note, or we can simply 
> >> remove it since section 6.4.4 of RFC 3550 already provides a 
> >> more-than-sufficient explanation.
> >>
> >> -acbegen
> >>
> >> _______________________________________________
> >> Audio/Video Transport Working Group
> >> avt at ietf.org
> >> https://www.ietf.org/mailman/listinfo/avt
> >>
> > 
> > 
> > 
>