Re: [MMUSIC] What is an m-line?
Harald Alvestrand <harald@alvestrand.no> Wed, 15 May 2013 20:04 UTC
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Date: Wed, 15 May 2013 22:04:44 +0200
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Subject: Re: [MMUSIC] What is an m-line?
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On 05/15/2013 08:47 PM, Bernard Aboba wrote: > <snip> > > So when people on the say "SIP equipment works this way" or "SDP works > this way" or even "RTP works this way" my BS meter goes off. Usually > they mean "the equipment I'm familiar with works this way". > > I'm not sure we can make a definitive statement about what "backwards > interoperability" means with respect to video systems today, at least > without some work to survey existing implementations. And this > somewhat complicates the "Plan A" vs. "Plan B" discussion in RTCWEB, > because the reality is that *neither* of these plans can achieve > widespread "backwards interoperability" with respect to SDP, if what > you mean by that is "I can take the SDP produced by a WebRTC > implementation, throw it over the wire to an existing implementation > and expect anything good to happen". Bravo! > > IMHO, it is unrealistic to expect *any* implementation of the current > WebRTC API to deliver that. Until "comment 22" is resolved, SDP > parsing/munging is going to be an unpleasant, time consuming but > necessary task for interop with legacy equipment. So as they said in > Dr. Strangelove, "stop worrying and love the bomb". I take a somewhat different approach: If it's possible to *write an application* that uses the WebRTC interface, does not mangle the SDP, and sends that to an existing implementation (supporting SRTP and ICE), and has something useful happen, I think it's the success we can hope for. This may mean having the application use content settings to force tracks to different m-lines, keep low the number of tracks offered, and other tricks that make sense in the context of *that application*. It's the *application* that needs to interwork, it's not "WebRTC in general". WebRTC just needs to make it possible. I see the idea that *any application* should produce SDP that's useful in such a scenario as an illusion, and pursuing that illusion is just going to hurt us. > > What I *would* like is for the RTP/RTCP produced by WebRTC > implementations to not require a compute intensive media > gateway/transcoder/munger to enable media to be handled by existing > systems, at least when the same video codecs are available (and no, > that shouldn't necessarily mean "video codec implementations based on > the same source code", because the spec should be good enough to > enable interoperability of independent implementations). I find nothing to disagree with in this paragraph.
- Re: [MMUSIC] What is an m-line? Paul Kyzivat
- Re: [MMUSIC] What is an m-line? Colin Perkins
- Re: [MMUSIC] What is an m-line? Bernard Aboba
- [MMUSIC] What is an m-line? Martin Thomson
- Re: [MMUSIC] What is an m-line? Paul Kyzivat
- Re: [MMUSIC] What is an m-line? Bernard Aboba
- Re: [MMUSIC] What is an m-line? Jonathan Lennox
- Re: [MMUSIC] What is an m-line? Martin Thomson
- Re: [MMUSIC] What is an m-line? Martin Thomson
- Re: [MMUSIC] What is an m-line? Cullen Jennings (fluffy)
- Re: [MMUSIC] What is an m-line? Martin Thomson
- Re: [MMUSIC] What is an m-line? Colin Perkins
- Re: [MMUSIC] What is an m-line? Kevin Dempsey
- Re: [MMUSIC] What is an m-line? Martin Thomson
- Re: [MMUSIC] What is an m-line? Colin Perkins
- Re: [MMUSIC] What is an m-line? Harald Alvestrand
- Re: [MMUSIC] What is an m-line? Bernard Aboba
- Re: [MMUSIC] What is an m-line? Martin Thomson
- Re: [MMUSIC] What is an m-line? Emil Ivov
- Re: [MMUSIC] What is an m-line? Martin Thomson
- Re: [MMUSIC] What is an m-line? Emil Ivov
- Re: [MMUSIC] What is an m-line? Martin Thomson
- Re: [MMUSIC] What is an m-line? Emil Ivov
- Re: [MMUSIC] What is an m-line? Paul Kyzivat
- Re: [MMUSIC] What is an m-line? Paul Kyzivat
- Re: [MMUSIC] What is an m-line? Paul Kyzivat
- Re: [MMUSIC] What is an m-line? Harald Alvestrand
- Re: [MMUSIC] What is an m-line? Paul Kyzivat
- Re: [MMUSIC] What is an m-line? Suhas Nandakumar