Re: [MMUSIC] WGLC on draft-ietf-mmusic-decoding-dependency-02

["Jean-Francois Mule" <jf.mule at cablelabs.com>]

Here are some comments on draft-ietf-mmusic-decoding-dependency-02.

1) Technical comments/questions:

- can you explain why the scope is limited to decoding dependencies of
the same media types?
> The SDP grouping of Media Lines of different media types
> is out of scope of this memo.
Are there specific issues that led to excluding this from the scope?  If
yes, having a sentence or two would be beneficial. 
What problems would we have if some folks were to use this 'depend'
attribute to mean rendering dependency? For example, render video stream
only if you render the audio stream.

- the examples in section 6.4 must have some explanation in plain
english of how to interpret the depend attribute value (agree with Ali
there)

- p9: "All media streams MUST contain at least one Operation point."
                        ^ in a decoding dependency group


2) Nits
- informative text
As you get the ID ready for publication, you may want to take another
pass at some of the informative text that you developed to justify the
draft in the first place.  For example:
"  At present, SDP and its extensions lack
   the means to express such a usage relationship."
=> this should be removed or replaced with something like: This document
defines an SDP extension to indicate such a decoding dependency.



- 'm='-line vs. media description or SDP media description
The issue is that a media description includes not only the m= line but
also others such as media attributes which are also important. SDP says:
"Each media description starts with an "m=" field and is terminated by
either the next "m=" field or by the end of the session description."
This is terminology but it is sometimes important in the text.

For example, 
	- page 8:
> The dependency signaling is only feasible between media descriptions
> described with an "m="-line and with an assigned media identification
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Implies media description == m=line
> attribute ("mid"), as defined in [RFC3388].  All "m=" lines grouped
> according to this specification MUST have the same media type.
Just say something like:
The dependency signaling is only feasible between media descriptions
with an assigned media stream identification attribute ("a=mid:").


   - page 9:
> All "m=" lines grouped
> according to this specification MUST have the same media type.
s/"m=" lines/media descriptions

- page 9: s/ an IETF standard's track document/ an IETF standards track
document
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