- From: Stefan Håkansson LK <stefan.lk.hakansson@ericsson.com>
- Date: Wed, 13 Apr 2011 13:35:19 +0200
-----Original Message----- From: Ian Hickson [mailto:ian@hixie.ch] Sent: den 12 april 2011 04:09 To: whatwg Subject: [whatwg] PeerConnection feedback >On Tue, 29 Mar 2011, Stefan H kansson LK wrote: >> > > > > The web application must be able to define the media format to >> > > > > be used for the streams sent to a peer. >> > > > >> > > > Shouldn't this be automatic and renegotiated dynamically via SDP >> > > > offer/answer? >> > > >> > > Yes, this should be (re)negotiated via SDP, but what is unclear is >> > > how the SDP is populated based on the application's preferences. >> > >> > Why would the Web application have any say on this? Surely the user >> > agent is in a better position to know what to negotiate, since it will >> > be doing the encoding and decoding itself. >> >> The best format of the coded media being streamed from UA a to UA b >> depends on a lot of factors. An obvious one is that the codec used is >> supported by both UAs.... As you say much of it can be handled without >> any involvement from the application. >> >> But let's say that the app in UA a does "addStream". The application in >> UA b (the same application as in UA a) has two <video> elements, one >> using a large display size, one using a small size. The UAs don't know >> in which element the stream will be rendered at this stage (that will be >> known first when the app in UA b connects the stream to one of the >> elements at "onaddstream"), so I don't understand how the UAs can select >> a suitable video resolution without the application giving some input. >> (Once the stream is being rendered in an element the situation is >> different - then UA b has knowledge about the rendering and could >> somehow inform UA a.) > >I had assumed that the video would at first be sent with some more or less >arbitrary dimensions (maybe the native ones), and that the receiving UA >would then renegotiate the dimensions once the stream was being displayed >somewhere. Since the page can let the user change the <video> size >dynamically, it seems the UA would likely need to be able to do that kind >of dynamic update anyway. Yeah, maybe that's the way to do it. But I think the media should be sent with some sensible default resolution initially. Having a very high resolution could congest the network, and a very low would give bad user experience until the format has been renegotiated. //Stefan
Received on Wednesday, 13 April 2011 04:35:19 UTC