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RE: Change Proposal for ISSUE-147

From: Ian Hickson <ian@hixie.ch>
Date: Thu, 17 Mar 2011 03:19:44 +0000 (UTC)
To: Frank Olivier <Frank.Olivier@microsoft.com>
cc: Silvia Pfeiffer <silviapfeiffer1@gmail.com>, "HTML WG (public-html@w3.org)" <public-html@w3.org>
Message-ID: <Pine.LNX.4.64.1103170313100.18930@ps20323.dreamhostps.com>
On Thu, 17 Mar 2011, Frank Olivier wrote:
> 
> >> . Setting playbackRate larger than 1.0 for live video will not work.
> > Sure it will, so long as the playhead is far enough back that there is 
> > buffered content to play.
>
> Sure, but what happens when you play through the buffered content and 
> get to (effectively) a live feed? The author should be able to determine 
> that effective playback rate is now 1.0 in this outcome - and setting to 
> >1.0 should not work.

The spec already covers this -- it's the same as what happens if you're 
playing at the rate of 1.0 but you're receiving only one second's worth of 
media every two seconds.

If we're agreed that the browsers _should_ support this, why would we make 
it effectively optional? Shouldn't this be a quality-of-implementation 
issue, where browsers try their best to approximate the requested rate and 
some do a better job than others? It would be equivalent to how some 
browsers can render canvas faster than others, or how some browsers render 
text more beautifully than others. We don't say that browsers that don't 
support rendering text well should simply refuse to add Text nodes to the 
DOM, right? Why would we require that browsers decide whether or not they 
can do a good enough job of going at the requested rate and force them to 
change the playbackRate accordingly?

Would reporting the playback quality (e.g. number of frames rendered over 
the past second of playback as a fraction of the number of frames that 
would ideally have been rendered during that same period) be an acceptable 
alternative solution?

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Thursday, 17 March 2011 03:20:14 GMT

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