Re: [rtcweb] Alternative Proposal for Dynamic Codec Parameter Change (Was: Re: Resolution negotiation - a contribution)
Magnus Westerlund <magnus.westerlund@ericsson.com> Wed, 25 April 2012 14:35 UTC
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Date: Wed, 25 Apr 2012 16:35:18 +0200
From: Magnus Westerlund <magnus.westerlund@ericsson.com>
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To: Justin Uberti <juberti@google.com>
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] Alternative Proposal for Dynamic Codec Parameter Change (Was: Re: Resolution negotiation - a contribution)
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On 2012-04-25 05:20, Justin Uberti wrote: > On Tue, Apr 24, 2012 at 10:25 AM, Magnus Westerlund > <magnus.westerlund@ericsson.com <mailto:magnus.westerlund@ericsson.com>> > wrote: > > A) Using COP and using SDP based signaling for the dynamic changes are > two quite different models in relation to how the interaction happens. > > For COP this all happens in the browser, normally initiated by the > browser's own determination that a COP request or notification is > needed. Harald's proposal appears to require that the JS initiate a > renegotiation. This puts a requirement on the implementation to listen > to the correct callbacks to know when changes happens, such as window > resize. To my knowledge there are not yet any proposals for how the > browser can initiate a JSEP renegotiation. > > > Maybe I misunderstand what you are saying, but the application will > definitely know when the browser size changes, and can then trigger a > JSEP renegotiation by calling createOffer and shipping it off. Yes, they can but that requires them to write code to do this. With COP the browser can do it and it works well for all applications, not only the ones that have implementors that are aware of the need to do this. I am proposing a mechanism that makes the default behavior if you care nothing about controlling or optimizing this behavior in your JS to be good. In addition JS that wants to control it can affect the behavior through generic mechanisms, such as controlling the video element. And if clear need is shown and some functionality is missing, W3C can create an API to provide explicit control. > > I have the opposite concern - how can the browser know when the > application makes a change, for instance to display a participant in a > large view versus a small view? This may be possible if using a <video/> > for display, but I don't think it will be possible when using WebGL for > rendering, where the size of the view will be dictated only by the > geometry of the scene. What I understand from my colleagues is that all rendering of video have to go through a video element, even if not displayed directly. Thus the application can control the size of the video element used and possibly consumed by WebGL to be included in rendering. Thus the application will have control over this even when COP is being used. Can you be more specific on any particular usage that you think would have issues? > > But I am worried that using SDP and with an API that requires the > application to listen for triggers that could benefit from a codec > parameter renegotiation. This will likely only result in good behavior > for the JS application implementors that are really good and find out > what listeners and what signaling tricks are needed with JSEP to get > good performance. I would much rather prefer good behavior by default in > simple applications, i.e. using the default behavior that the browser > implementor have put in. > > > The issue here is that this behavior needs to be sufficiently specified, > or else we will have many different behaviors, none of which can be > fully overridden by the app. I worry this will make life hard for people > trying to develop sophisticated apps. I agree that it needs to be clearly specified. But COP appears to be less prone to complete failures by using target values. Then at least it will receive video that can be used, even if not optimal. imageattr can result in failures in the negotiation requiring at minimal a second round potentially no agreed on acceptable resolution then that is clearly sub-optimal. That is even without considering involving JS mainipulating this. Cheers Magnus Westerlund ---------------------------------------------------------------------- Multimedia Technologies, Ericsson Research EAB/TVM ---------------------------------------------------------------------- Ericsson AB | Phone +46 10 7148287 Färögatan 6 | Mobile +46 73 0949079 SE-164 80 Stockholm, Sweden| mailto: magnus.westerlund@ericsson.com ----------------------------------------------------------------------
- [rtcweb] Resolution negotiation - a contribution Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - a contribut… Timothy B. Terriberry
- Re: [rtcweb] Resolution negotiation - a contribut… Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - a contribut… Marshall Eubanks
- Re: [rtcweb] Resolution negotiation - a contribut… Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - a contribut… Stephan Wenger
- Re: [rtcweb] Resolution negotiation - a contribut… Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - a contribut… Stephan Wenger
- Re: [rtcweb] Resolution negotiation - a contribut… Harald Alvestrand
- [rtcweb] VP8 payload, decoder processing capabili… Stephan Wenger
- Re: [rtcweb] [payload] VP8 payload, decoder proce… Yuepeiyu (Roy)
- Re: [rtcweb] Resolution negotiation - mandatory /… Roni Even
- Re: [rtcweb] Resolution negotiation - mandatory /… Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - mandatory /… Roni Even
- Re: [rtcweb] Resolution negotiation - mandatory /… Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - mandatory /… Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - mandatory /… Roni Even
- [rtcweb] Alternative Proposal for Dynamic Codec P… Magnus Westerlund
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Harald Alvestrand
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Timothy B. Terriberry
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Bernard Aboba
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Harald Alvestrand
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Justin Uberti
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Magnus Westerlund
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Harald Alvestrand
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Magnus Westerlund
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Justin Uberti
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Magnus Westerlund
- Re: [rtcweb] [payload] VP8 payload, decoder proce… Cullen Jennings (fluffy)
- Re: [rtcweb] [payload] VP8 payload, decoder proce… Harald Alvestrand