Re: [payload] Significant Differences Between draft-ietf-payload-rtp-ancillary-08 and -09

[John Fletcher <[e-mail]>]

My concern is that there are two sets of data stream numbering in ST 425-3 Figure 2.  In each link they are numbered 1 & 2.  So the language needs to make it clear that we are numbering 1 - 4.

How about adding the following text:

Numbering of data streams is across the interface as a whole.  For example in the SMPTE ST 425-3 dual-link 3 Gb/s interface, the data streams are numbered 1 - 4 with data streams 1 and 2 on link 1 and data streams 3 and 4 on link 2.

John
________________________________
From: payload [[e-mail]] on behalf of Thomas Edwards [[e-mail]]
Sent: 15 May 2017 18:56
To: [e-mail]
Subject: Re: [payload] Significant Differences Between draft-ietf-payload-rtp-ancillary-08 and -09

I don’t see the problem – In ST 425-3 there are four data streams numbered 1-4, and Figures 1 & 2 show that data streams 1 & 2 go on 3G SDI link #1, and streams 3 & 4 go on 3G SDI link #2.

If you are concerned about the fact that the 3G SDI link itself (ST 424) also has two data streams each, that also should not matter because the ST 425-3 data streams also clearly define which of those ST 424 data streams are used (i.e. ST 425-3 data stream #3 is carried on 3G-SDI Link #2, ST 424 data stream #1).   I think it should be clear that if the VPID Code refers to “1080-line Video Payloads for Level A Mapping on a Dual-link 3 Gb/s (nominal) Serial Interface” that the stream number we are describing is from that standard, and not the stream number from ST 424.  That said, I blame SMPTE for not providing an appropriate adjective (such as “image stream number” or “link stream number”), but I think that it is perilous for IETF to invent one for them.

BTW I understand why link numbers are carried in the VPID – the goal of the VPID is to describe the video format and to help you plug the coaxial cables into the proper connector.  Once the coaxes are plugged in properly, the stream numbers follow naturally based on timing, so a VPID ANC packet does not need to be in every data stream, just on at least one per link.

If I am missing something and you have alternative suggested language, please provide it.

-Thomas

From: John Fletcher <[e-mail]>
Date: Monday, May 15, 2017 at 9:02 AM
To: Thomas Edwards <[e-mail]>, "[e-mail]" <[e-mail]>
Subject: RE: Significant Differences Between draft-ietf-payload-rtp-ancillary-08 and -09

Section 2.1 "StreamNum" doesn't give enough information about numbering of the data streams.  For example, in dual-link 3G there are 4 data streams split across two links, see ST 425-3 Figure 2.



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