Re: [payload] WGLC for draft-ietf-payload-rtp-vc2hq-01

[Thomas Edwards <[e-mail]>]

I will preface this with the fact that I am NOT a VC-2 expert.  But I am very glad to see this I-D making progress.  So here we go:

Comments on draft-ietf-payload-rtp-vc2hq-01 from Thomas Edwards:

“At time of writing there is currently no definition for the use of
   Auxiliary Data in VC-2, and Padding Data is required to be ignored by
   all receivers.”

“  Since there is no definition for the use of Auxiliary Data Units and
   Padding Data Units are defined by the VC-2 spec to be ignored by all
   decoders this specification only covers the transport of Sequence
   Headers, High Quality Pictures, and (optionally) End of Sequence
   headers.”

SMPTE ST 2042-1 does define the structure of Auxiliary Data and Padding.  While this payload definition does not need to normatively say anything about receiver behavior regarding these fields, I feel that Auxiliary Data and Padding should be able to be carried in this payload.

“These four packet-types can be distinguished by the fact that they
   use different codes in the "PC" field,”

Suggest expand “PC so it becomes  ‘the “PC” (Parse Code) field’ as this is first use of “PC”.

Might want to be clear that the “F” bit doesn’t apply to progressive pictures.

I am concerned about the bit limitation on slice_prefix_bytes and slice_size_scalar.  While in practice 16 bits might be enough, it looks like ST 2042-1 has no limit, and instead a length/value combo might be more appropriate.

It scares me a bit that this draft is defining new parse codes, as opposed to using a fragmentation flag (or fragment number) in the payload header.  It may be confusing to implementers.

-Thomas

--
Thomas Edwards
VP Engineering & Development
FOX Networks Engineering and Operations
[e-mail]
Phone: [phone]
10201 West Pico Blvd.
Los Angeles, CA 90035

From: "Ali C. Begen" <[e-mail]>
Date: Tuesday, April 4, 2017 at 7:40 AM
To: "[e-mail]" <[e-mail]>
Cc: Thomas Edwards <[e-mail]>
Subject: Re: WGLC for draft-ietf-payload-rtp-vc2hq-01

Any other comments on this draft? So far, we heard from Jean-Marie and Victor supporting the draft. If you have any comments, please send them by next Wed (April 12th).

@Thomas

I believe you volunteered to review this draft? Could you submit it by next week?

Thanks.
-acbegen (co-chair)

On Fri, Feb 24, 2017 at 9:02 AM, Ali C. Begen <[e-mail]<mailto:[e-mail]>> wrote:
WG,

We are starting WGLC for the following draft. Please review the draft and send your comments to the list by March 13th. If you read the draft but you have no comments, say so as well.

It is a short document, so should be a quick review.
https://datatracker.ietf.org/doc/draft-ietf-payload-rtp-vc2hq/<https://urldefense.proofpoint.com/v2/url?u=https-3A__datatracker.ietf.org_doc_draft-2Dietf-2Dpayload-2Drtp-2Dvc2hq_&d=DwMFaQ&c=uw6TLu4hwhHdiGJOgwcWD4AjKQx6zvFcGEsbfiY9-EI&r=lekNOOM5noV61zrPH3rwPyhtNnLLWoLEHgd0quQxly8&m=nODGKNtr0Ro-UX0laVDU6Xf_tCrbxuTrZ74oSLwzCeg&s=rMSMDntd8k0qHAsmU3Bqlfg8WUoQrW-0nT5O_jIwFbs&e=>

-acbegen