[MMUSIC] Issue with RID draft: support for "pt=" should be optional

[Peter Thatcher <[e-mail]>]

Currently, all attributes/constraints on an a=rid line are optional.  For
example, if the offer contains this:

a=rid:A send
a=rid:B send
a=simulcast rids:A,B

and the answer contains this:

a=RID:A recv max-fs=15
b=RID:B recv max-fs=15
a=simulcast rids:A,B

That's an error because the offer indicated no support for max-fs.


However, currently in the draft (if I'm reading it correctly), the answer
can contain this:

a=RID:A recv pt=1,2
b=RID:B recv pt=3,4
a=simulcast rids:A,B


This is problematic for two reasons:

1.  It's not consistent with all of the other attributes/constraints.

2.  Like many of the other attributes/constraints (which are optional), pt
doesn't map well to the WebRTC API, which means it will make sense to not
support pt constraints in WebRTC 1.0.  But if it remains mandatory in this
draft, then the draft may end up being incompatible with WebRTC 1.0.


I propose we treat pt= just like max-fs= and max-width=, etc, and make it
optional.  Otherwise we risk ending up with a draft that we can't use for
WebRTC 1.0 anyway.   Plus, it would be more consistent with all the other
attributes/constraints on an a=rid line.