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Re: <video> and <audio> (was RE: Implementor feedback on new elements in HTML5)

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Fri, 13 Nov 2009 22:51:55 +1100
Message-ID: <2c0e02830911130351l5ef76724q6e3c9e29e9a1ea65@mail.gmail.com>
To: Henri Sivonen <hsivonen@iki.fi>
Cc: peter.jaderlund@infocaption.com, public-html@w3.org
On Fri, Nov 13, 2009 at 10:38 PM, Henri Sivonen <hsivonen@iki.fi> wrote:
> On Nov 13, 2009, at 08:10, Peter Jäderlund wrote:
>
>>   <media target="mobile">
> [...]
>>   <media target="web">
>
> This design assumes that mobile is equally bad across all user locations around the globe and across all devices.
>
> The key issues are bandwidth (which varies greatly) and the device's ability to decode video of different sizes in real time.
>
> A more appropriate way of providing UA-selected alternatives would be attaching a Media Query to each <source> and extending Media Queries to query bandwidth and some kind of decode performance metric. (Unfortunately, the latter is probably hard to represent as an intuitive and easily measurable scalar.)

An example of a media query was presented by Dave Singer at the recent
Video A11y workshop. I am taking the freedom to cite him, though I'm
not sure it's completely accurate.

<video ...>
  <source media="accessibility(captions:yes)" src="A"/>
  <source media="accessibility(captions:no audiodescription:yes)" src="B"/>
</video>

I guess that could be extended to cover bandwidth and intended size
etc. and can help a User Agent decide which alternative tracks/videos
he can choose from.

I still believe there is a need to allow us to describe alternative
and additive tracks/videos. For example, a video element that has one
main source element with the A video, and a set of alternative sign
language tracks that are additional video to A is very difficult to
describe in a flat structure like this. One additional structuring
level might be helpful. OTOH, if we can avoid it, it's good, too,
because we don't want to pollute html with even more element names.

Cheers,
Silvia.
Received on Friday, 13 November 2009 11:52:47 UTC

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