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Re: Tech Discussions on the Multitrack Media (issue-152)

From: Mark Watson <watsonm@netflix.com>
Date: Thu, 3 Mar 2011 09:51:47 -0800
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
CC: Philip Jägenstedt <philipj@opera.com>, "public-html@w3.org" <public-html@w3.org>
Message-ID: <52070170-7A88-4600-BAB9-E537C199E1AB@netflix.com>

On Mar 2, 2011, at 4:38 PM, Silvia Pfeiffer wrote:

> On Thu, Mar 3, 2011 at 3:40 AM, Mark Watson <watsonm@netflix.com> wrote:
>> 
>> 
>> I have another question related to an earlier discussion on this thread: do I understand correctly that in order to apply CSS styling there needs to be an HTML markup element to apply the styling to ? i.e. that you couldn't apply styling to control the rendering of an in-band track that appears only as a MediaTrack object and not as a <track> element (with associated HTMLTrackElement object) ?
>> 
>> In that case it seems we need to be able to refer to an in-band track in the main resource from a <track> element in order to apply styling. For example the MediaTrack API could expose an "id" attribute (at least for in-band tracks) which could be used to refer to this track from a <track> element.
> 
> 
> I didn't want to let this one go unnoticed. In the current spec for
> <track> we address the cues inside the <track> - independent of
> whether they come from in-band or from an external file - through a
> ::cue CSS pseudo-selector.
> 
> Maybe something like this can be introduced for the tracks, too? This
> could then avoid having a HTML markup element for tracks and allow us
> to style them similar to how we style cues. Can this work:
> ::track(number) where number is the position in the IDL tracks list in
> the HTMLMediaElement? Some kind of default rendering would need to be
> described, too.
> 

I don't have a strong opinion on the solution, just that it should be possible to control the rendering of in-band tracks as well as those which are explicitly declared in the markup.

Do I understand correctly that to style WebVTT with CSS you attach a styles to the HTMLMediaElement containing the :cue pseudo-selector and these apply to both in-band and explicitly defined timed text tracks ?

To apply the same to other tracks, then it still might be better to require some kind track id and then the pseudo-selector would be :track(id). I say this because I expect that in-band tracks might be added or removed during playback and so the numbering will change. For example, accessibility tracks may be available for the main content but not for adverts. Or in a long-lived live stream things will change from show to show.

I expect we will need an event to indicate when the in-band tracks change.

...Mark

...Mark


> Cheers,
> Silvia.
> 
Received on Thursday, 3 March 2011 17:52:51 GMT

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