Subject: [Gen-art] Gen-art LC review of draft-ietf-payload-rtp-ancillary-06

From: Christer Holmberg <[email-masked]>
Date: Thu, 27 Oct 2016 12:30:06 +0000

I am the assigned Gen-ART reviewer for this draft. For background on
Gen-ART, please see the FAQ at
<http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>

Document:            draft-ietf-payload-rtp-ancillary-06
Reviewer:            Christer Holmberg

Review Date:         26 October 2016
IETF LC End Date:    3 November 2016
IETF Telechat Date:  N/A

Summary:

The document is well written, and is almost ready for publication as
standards track RFC. However, I have some issue regarding the SDP sections
(see below).

Major Issues:           None

Minor Issues:      

Q0: Section 3.1:

    The text talks about what the presence of DID and SDID means. But, as
they are optional, what does it mean if they are NOT present?

Q1: Section 3.2:

    1) I would suggested that the section is renamed to ³SDP
Considerations², and becomes a level 1 section (i.e., ³4 SDP
Considerations²).

    2) Is it allowed to carry both a ³normal² video stream and the ANC RTP
payload within the same m= line? If so, how are they related?

    Example:

    v=0
    o=Al 123456 11 IN IP4 host.example.com
    s=Professional Networked Media Test
    i=A test of synchronized video and ANC data
    t=0 0
    m=video 50000 RTP/AVP 96 97
    c=IN IP4 233.252.0.1/255
    a=rtpmap:96 raw/90000
    a=fmtp:96 sampling=YCbCr-4:2:2; width=1280; height=720; depth=10
    a=rtpmap:97 smpte291/90000
    a=fmtp:97 DID_SDID={0x61,0x02};DID_SDID={0x41,0x05}

    3) Is it allowed to use two or more ANC RTP payloads (e.g., each using
a different DID_SDID), either within a single m- line, or within different
m- lines? If so, how are they related?

    4) When I indicate DID_SDID, it is something I intend to SEND, or
something I am willing to RECEIVE?

    5) If multiple DID_SDIDs are listed, can they be used in any order
during the session? If so, it would be good to explicitly indicate that,
and note that the same payload type value will be used for all of them.

    6) Is there a possibility that the receiver does not understand
DID_SDID, or specific DID_SDID values? If so, what shall it do?

Q2: Section 3.2.1:

   The text says:

   "The ANC RTP payload format will often be used in groupings with
   associated video streams.  Any legal SDP grouping mechanism could be
   used."

   1) What is meant by the second sentence (³any legal SDP grouping²)?
Isn¹t the semantic depending on the type of grouping?

   2) What if the SDP group contains two (or more) video m= lines. Is the
ANC RTP payload then associated with all of them?

   3) Could you rename the section title to "Grouping ANC Streams with
Video Streams²?

Q3: Section 3.3:

   1) You should say something about updating the parameters in a
sub-sequent offer (or within an answer to an sub-sequent offer). Are there
any restrictions?

   2) What does it mean if one sends a sub-sequent offer/answer without
some/all parameters. Does it mean they are disabled?

   3) Is it allowed to include ANC RTP in an answer if the offer doesn¹t
contain it?

   4) Is is allowed to include DID_SDID in an answer if not included in
the offer?

   5) Can the DID_SDID values in the answer be different than the ones in
the offer, or are there any restrictions?

Editorial Issues:       None