Re: [MMUSIC] [rtcweb] Fwd: New Version Notification for draft-uberti-rtcweb-plan-00.txt

Christer Holmberg <> Tue, 07 May 2013 17:03 UTC

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From: Christer Holmberg <>
To: Harald Alvestrand <>
Thread-Topic: [rtcweb] Fwd: New Version Notification for draft-uberti-rtcweb-plan-00.txt
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Date: Tue, 7 May 2013 17:03:21 +0000
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Subject: Re: [MMUSIC] [rtcweb] Fwd: New Version Notification for draft-uberti-rtcweb-plan-00.txt
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>>>> Q2_2_LEGACY:
>>>> The example in section 5.2 (and sub sections) confuses me a little. You indicate that the m- line itself represents "main", while ssrc
>>>> attributes are used to describe the left/center/right mic sources. Why is there no ssrc attribute for the main flow?
>>> The MSID identifier is, by definition, meaningless. The association between the MSID and the function of the stream is not carried in
>>> the MSID attribute. The example is a bit unfortunate in that it uses MSIDs that look as if they're human-readable strings that carry semantics.
>> I wasn't referring to the MSID identifier, but more to the fact that you don't indicate the ssrc value for the "main" flow. I thought we were going to mandate the indication of the ssrc value for each flow, but maybe I remember wrong.
> I was trying to locate the flows in the example in section 5.2, and I 
> couldn't find them anywhere but in the MSID attribute. So I couldn't 
> parse your comment.
> The way I read the document, the first m=audio line is the main audio; 
> it has 3 audio flows.
> The first m=video line is the main video; it has 3 video flows.
> The third m=video line is the slides video; it has 2 SSRCs, one for the 
> main flow and one for the repair flow.
> So - the issue seems to be that the word "main" as in "main audio" is 
> easy to mistake for "a single main flow". It isn't intended to be that 
> way. I guess the text could be clearer.

That is how I understood it - that "main" is a flow by itself, separate from the left/center/right mic flows :)

Maybe "media description for main audio flows" would be a move clear description, rather than simply "main audio".