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[whatwg] Quality Values for Media Source Elements

From: Eric Carlson <eric.carlson@apple.com>
Date: Sun, 13 Dec 2009 21:12:32 -0800
Message-ID: <0D18D762-EDF0-42C7-B2C5-EB154163A738@apple.com>

On Dec 13, 2009, at 8:12 PM, Silvia Pfeiffer wrote:

> Oh! What are you doing with it? I mean - have the values in the media
> attribute any effect on the video element?
> 
  Certainly! WebKit evaluates the query in the 'media' attribute if it believes it can handle the MIME type. If the query evaluates to true, it uses that <source> element. If it evaluates to false it skips it, even though it could (in theory) open the movie. For example, one of our layout tests [1] has the following :

<video controls>
    <source src=content/error.mpeg media="print">
    <source src=content/error2.mpeg media="screen and (min-device-width: 80000px)">
    <source src=content/test.mp4 media="screen and (min-device-width: 100px)">
</video>

  The test fails if the video element is instantiated with anything but "test.mp4".

  I have seen 'media' used on real-world pages with something like the following to select different movies for the iphone and desktop:

<video controls>
    <source src='desktop-video.mp4' media="@media screen and (min-device-width: 481px)">
    <source src='iphone-video.mp4' media="@media screen and (min-device-width: 480px)">
</video>

  This works because the <source> elements are evaluated in order, so the first one is selected on the desktop where both queries will evaluate to true.

eric

[1] http://trac.webkit.org/browser/trunk/LayoutTests/media/video-source-media.html?format=txt


> Thanks,
> Silvia.
> 
> On Mon, Dec 14, 2009 at 2:43 PM, Eric Carlson <eric.carlson at apple.com> wrote:
>> 
>> On Dec 13, 2009, at 2:35 PM, Silvia Pfeiffer wrote:
>> 
>>> This is why the @media attribute hasnt' been used/implemented anywhere yet
>>> 
>>  Are you saying that nobody has implemented the "media" attribute on <source>? If so, you are incorrect as WebKit has had this for almost two years.
>> 
>> eric
>> 
>> 
Received on Sunday, 13 December 2009 21:12:32 UTC

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