Re: [MMUSIC] Possible BUNDLE alternative syntax: explicit m-line for bundled session

"Parthasarathi R" <> Sun, 23 September 2012 18:50 UTC

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From: Parthasarathi R <>
To: 'Christer Holmberg' <>, 'Lishitao' <>, "'Ejzak, Richard P (Richard)'" <>,
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Date: Mon, 24 Sep 2012 00:20:44 +0530
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Subject: Re: [MMUSIC] Possible BUNDLE alternative syntax: explicit m-line for bundled session
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Hi Christer,

IIUC, The same port offer may be rejected by answerer irrespective of 
"m=bundle" or "a=group:BUNDLE" as it is not just new SDP syntax
but also, the same port offer may have impact in other layers like RTP 
in answerer side implementation. The bundling of the different media 
in the same port is not guaranteed to negotiate in the answer side with 
"m=bundle" mechanism. The point is that answerer will reject in case the 
same port offer is not accepted in the specific implementation.

Apart from this, The individual attribute behavior for bundle has to be 
defined somewhere irrespective of "m=bundle" or "a=group:BUNDLE". Say ptime 
attribute applies for the audio codecs only or applies for video codecs
as well in the bundle has to be defined. I'm not see much advantage with 
"m=bundle" here. Instead, Let us discuss the generic categories of
and mention in this draft.


-----Original Message-----
From: Christer Holmberg [] 
Sent: Friday, September 21, 2012 10:57 PM
To: Parthasarathi R; 'Lishitao'; 'Ejzak, Richard P (Richard)';
Subject: RE: [MMUSIC] Possible BUNDLE alternative syntax: explicit m-line
for bundled session


>I agree with Cullen & others that m=bundle does not have consensus. We need
>more discussion and analysis. The current Bundle syntax is designed in a
>to reuse lot of existing SDP mechanism (Syntax & Semantics). If possible,
>let us try to fix the open issue with the current mechanism before
>with m=bundle approach.

Feel free to provide input on how you think we can solve that issue :)



-----Original Message-----
From: [] On Behalf Of
Sent: Friday, September 21, 2012 7:21 AM
To: Christer Holmberg; Ejzak, Richard P (Richard);
Subject: Re: [MMUSIC] Possible BUNDLE alternative syntax: explicit m-line
for bundled session

> -----Original Message-----
> From: [] On Behalf
> Of Christer Holmberg
> Sent: Friday, September 21, 2012 3:32 AM
> To: Ejzak, Richard P (Richard);
> Subject: Re: [MMUSIC] Possible BUNDLE alternative syntax: explicit m-line
> bundled session
> Hi,
> >>> m=bundle requires significant extensions to the syntax and also a near
> >>> doubling in the size of the SDP.  It is harder to specify allowed
> >>> combinations of codecs and other options that are normally associated
> >>> with a single m line.
> >>
> >> Please give an example.
> >
> > To specify two types of audio flows with very different characteristics
I would
> normally have separate media lines with separate codec lists and
> One may require DTMF and the other silence suppression in addition to the
> selected (but different)
> > codecs.  We need to keep this characteristic.  We also need a way of
> specifying bandwidth per (old) media line, which is already supported
> separate media lines but requires that something new be defined for
> What about RTCP
> > characteristics?  We certainly want to specify them per (old) media
> >
> > I understand that this can be done with m=bundle, but it requires new
> Why bother if we have something that can work?
> I am not sure it requires new syntax, if you e.g. can use the ssrc
attribute in
> order to map attributes to specific flows.

I would suggest that put the m=bundle proposal in a separate new personal
draft or in the annex of the existing working draft, and
make a comparison for this proposal and the existing proposal. That will
make it more clear.
For the existing proposal, I believe that people are not totally against,
although it has some issues. (the m=bundle proposal also has some issues).


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