Subject: [AVTCORE] AD Review of draft-ietf-payload-vp9-12

From: "Murray S. Kucherawy" <[email-masked]>
Date: Mon, 19 Apr 2021 15:32:36 -0700

This is my review of draft-ietf-payload-vp9-12.

Video codecs are not exactly my strong suit, so finding technical errors
wasn't an expected part of my mission here.  I'm going on faith that this
is all technically correct, and just looking for editorial or procedural
things.

-MSK

--

Shepherd writeup:

* We should probably explain why a document coming out of AVTCORE bears a
name that doesn't start with "draft-ietf-avtcore-...".  The shepherd
writeup should mention this.  Or if you don't want to do that, please let
me know what the history is there so I can include it in a note to the IESG.

* The writeup identifies draft-ietf-avtext-lrr as a downward reference, but
that document is in the queue already for Proposed Standard status, and
this one is going for the same, so I don't believe this is a downward
reference (once both are published).

General nits:

* Referring to an I-D as a "memo" is a little outdated.  Suggest "document"
or "specification" instead.

Section 1:

* Should this document obsolete VP8 (RFC 6386)?

Section 3:

* The Editor's Note seems like it should've been resolved by now.  If no
suggestion for improved terminology arrives by the end of IESG Evaluation,
should that paragraph be removed?

Section 4.1:

* For "Timestamp", did you mean to say "alternately" (i.e., every other
one; alternating) or "alternatively" (i.e., presenting a different choice)?

Section 4.2:

* First sentence, "The" shouldn't be capitalized.

* The use of CONDITIONALLY RECOMMENDED or CONDITIONALLY REQUIRED is
puzzling because one of them is a BCP 14 word and one isn't, but both look
like they're supposed to be.  This might be better described in the prose
for each of these fields, and just use the BCP 14 words here (or omit them
entirely).

* The description of PID refers to a "maximum ID", but that's not specified
anywhere.  Is it simply the largest PID that will fit in the available
bits, or is there some other maximum to be observed?

* For the "D:" bullet, I think "MUST be set to one if current spatial layer
SID frame depends on spatial layer SID-1 frame of the same picture. MUST
only be set to zero if current spatial layer SID frame does not depend on
spatial layer SID-1 frame of the same picture." can be reduced to "MUST be
set to one if and only if the current spatial layer SID frame depends on
spatial layer SID-1 frame of the same picture."

Section 6.1:

* Does the media type's subtype name have to be "VP9", in specifically that
case?

* Per RFC 6838, please change Required Parameters to "N/A" instead of
"None".

* I think it's unusual for the BCP 14 text to appear in a media type
registration (specifically, the Optional Parameters).  You might consider
moving that discussion to some other prose section, and in the media type
registration just list the supported parameters and their syntaxes.