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Re: [MMUSIC] Updated MSID draft

Paul Kyzivat <pkyzivat@alum.mit.edu> Wed, 30 October 2013 14:39 UTC

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Date: Wed, 30 Oct 2013 10:38:34 -0400
From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Subject: Re: [MMUSIC] Updated MSID draft
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A few comments about this version. Actually the comments aren't specific 
to this revision, but they relate to things I didn't notice earlier.

Msid-Semantic syntax:

      attribute =/ msid-semantic-attr
      msid-semantic-attr = "msid-semantic:" token (" " identifier)*
      token = <as defined in RFC 4566>

The usage of "*" is backward. (Following regex syntax rather than abnf 
syntax). This ought to be:

      attribute =/ msid-semantic-attr
      msid-semantic-attr = "msid-semantic:" token *(" " identifier)
      token = <as defined in RFC 4566>

Just following that:

    The semantic field may hold values from the IANA registries
    "Semantics for the "ssrc-group" SDP Attribute" and "Semantics for the
    "group" SDP Attribute".

I have a couple of issues with this:

Section 5 defines a new registry "Semantics for the msid-semantic SDP 
attribute", and defines a new semantic "WMS" in it. The text above 
doesn't even reference this registry.

Because the two mentioned registries are independent, AFAIK there is no 
guarantee that they couldn't someday contain different definitions for 
the same "semantic" name. Then, if that name were used with msid the 
proper definition to use would be ambiguous. (I realize this is 
implausible, but nothing prevents it.) IMO the *right* answer would be 
to merge all these grouping semantics into a single table. But that is a 
hassle right now. Perhaps it would be sufficient to say that only 
semantics that are uniquely defined across all of these tables may be 
used with msid. E.g.,

    The semantic field may hold any value that is uniquely defined
    in one and only one of the IANA registries "Semantics for the
    msid-semantic SDP attribute", "Semantics for the "ssrc-group"
    SDP Attribute" and "Semantics for the "group" SDP Attribute".

	Thanks,
	Paul

On 10/30/13 3:13 AM, Harald Alvestrand wrote:
> Roni and Flemming pointed out that I hadn't managed to submit the fixes
> I made to -msid after the reviews of -01 before the deadline, and had
> even managed to forget to send it to the list.
>
> I had missed a number of occurences where "SSRC" needed to be changed to
> "m-line" in the text (with some more adjustments to language around that).
>
> Here it is. I'll submit it on Monday, when the I-D repository reopens.
>
>
>
> _______________________________________________
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> mmusic@ietf.org
> https://www.ietf.org/mailman/listinfo/mmusic
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