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Re: [MMUSIC] BUNDLE: no reason por payload type to be unique within bundled m= lines

Colin Perkins <csp@csperkins.org> Thu, 10 March 2016 00:02 UTC

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From: Colin Perkins <csp@csperkins.org>
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Date: Thu, 10 Mar 2016 00:02:29 +0000
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References: <CALiegfm7Rb4e5DFGycr=EsdigE1XFCUiqNL6+GpRSyrGe=_RWg@mail.gmail.com> <56DED735.1000101@ericsson.com> <CALiegf=G77JOcoR6DORnPsMx4OCgy=_dYQ_r8KfjMy_33vn89A@mail.gmail.com> <7594FB04B1934943A5C02806D1A2204B37E9EA74@ESESSMB209.ericsson.se> <CALiegf=F4z9r+oCO1DMW_nXq7TBJjf-n3N1r6yr5tLoksXtUqg@mail.gmail.com> <6D5F352C-34B2-4415-A731-051CB44E99AC@csperkins.org> <CAJrXDUGvvmiLRnywEZ6GHUC2xrjJ9528c1w4TpH9VV5Ov04ebQ@mail.gmail.com>
To: Peter Thatcher <pthatcher@google.com>
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Cc: Christer Holmberg <christer.holmberg@ericsson.com>, "mmusic@ietf.org" <mmusic@ietf.org>, Magnus Westerlund <magnus.westerlund@ericsson.com>
Subject: Re: [MMUSIC] BUNDLE: no reason por payload type to be unique within bundled m= lines
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> On 9 Mar 2016, at 23:51, Peter Thatcher <pthatcher@google.com> wrote:
> 
> 
> 
> On Wed, Mar 9, 2016 at 3:35 PM, Colin Perkins <csp@csperkins.org <mailto:csp@csperkins.org>> wrote:
> 
> > On 8 Mar 2016, at 23:34, Iñaki Baz Castillo <ibc@aliax.net <mailto:ibc@aliax.net>> wrote:
> >
> > 2016-03-08 20:05 GMT+01:00 Christer Holmberg <christer.holmberg@ericsson.com <mailto:christer.holmberg@ericsson.com>>:
> >> When we discussed payload type mappings and RTP sessions, it was said that, in a sendonly m- line, the payload type values are simply "place holders", the remote endpoint will tell you what values it want to receive.
> >>
> >> So, in your case, you can't say "I am going to send you with PT 100". The answerer is going to say what it wants to receive, so in your case it may e.g. chose 98 for alice-audio and 99 for bob-audio.
> >
> > So I tell you that I will send N codecs with SSRC 1234 and you tell me
> > which payload I should use. This makes no sense IMHO. SDP was designed
> > for 1-to-1 symmetric (audio) streams.
> 
> No, SDP was designed to advertise multiparty multicast conferences on the Mbone, in declarative mode, using SAP for session discovery. Use with SIP and offer/answer came later.
> 
> 
> ​So that's how we got into this m... I mean, thanks for the tidbit of history.  It's inter​esting.  Do you have link to a place where the history is written down?  If not, could you right it down?  I'm seriously interested to know the history a bit to know how we got here.


ftp://ftp.isi.edu/isi-pubs/rs-92-293.pdf <ftp://ftp.isi.edu/isi-pubs/rs-92-293.pdf> might be an interesting starting point. Or old MMUSIC minutes (this was already ongoing discussion in MMUSIC at IETF 37, which was my first meeting).

-- 
Colin Perkins
https://csperkins.org/

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