[rtcweb] JSEP-04: Nits and niggles

[Harald Alvestrand <[e-mail]>]

I'm sure we'll have lots of things to discuss about JSEP. I just thought 
I'd get these out of the way.

- Usage of MSID. In addition to the a=msid: lines, the session-level 
generation procedure needs to say that a line "a=msid-semantic:WMS <id>" 
is added to the session-level description, containing the IDs of the 
MediaStreams that are signalled.

- a=ssrc lines. The spec (5.2.1 second list last bullet) simply says "an 
a=ssrc line". But RFC 5576 specifies that all ssrc lines contain an 
attribute. Suggestion: define one that does no harm (role=primary?)

- recycling of m= lines. The section in 5.2.2 (subsequent offers) that 
talks about this doesn't mention that the media in the m-line has to 
match, although section 5.3.1 (initial answer) actually talks about it. 
I'm assuming that's an oversight.

I'd suggest pulling the language about "selecting an appropriate m-line 
for a track" out in a separate subsection, so that we have one place to 
point to for this.

Out of time, let's get these ones out of the way for -05....