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Re: [MEDIA_PIPELINE_TF] ISSUE-34: ViewPort-Support

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Thu, 11 Aug 2011 20:34:55 +1000
Message-ID: <CAHp8n2=u-4=s39otZZXBQ_bQCjZwnuz-cQk4p52wsVyMz7VtKw@mail.gmail.com>
To: Cyril Concolato <cyril.concolato@telecom-paristech.fr>
Cc: public-web-and-tv@w3.org
On Thu, Aug 11, 2011 at 7:35 PM, Cyril Concolato
<cyril.concolato@telecom-paristech.fr> wrote:
> Hi Sylvia,
>
>> Can you fill the TextTrack object and the cues from a SVG? As long as
>> you can make a mapping, it's possible. If the format doesn't fit with
>> the elements, then it's an orthogonal concept that won't fit the bill.
>
> Reading http://www.w3.org/TR/html5/video.html#text-track it says:
> "A text track consists of:"
> * "The kind of text track": would apply to SVG tracks
> * "A label": would apply to SVG tracks
> * "A language": would apply to SVG tracks
> * "A readiness state": would apply as well
> * "A mode": same
> * "A list of zero or more cues"
>
> A Cue is defined as:
> * "An identifier": applicable to SVG tracks
>
> * "A start time"/"An end time":
> As such SVG does not define frame-based content as Flash would do or other
> subtitling formats, but you can define frame-based content such as:
> http://perso.telecom-paristech.fr/~concolat/SVG/flash8.svg

This is one of the major requirements. Trust me - SVG won't fit the
bill as a time-aligned data format. And browsers won't implement it.
But you can always try a JavaScript implementation to prove me wrong.

Cheers,
Silvia.


>
> * A pause-on-exit flag:
> not sure what it means but seems applicable
>
> * A writing direction: when restricted to unidirectional text content, it
> would be applicable but I don't see it in the TextTrackCue object
> (http://www.w3.org/TR/html5/video.html#texttrackcue)
>
> * A size:
> not sure I understand why it's not 2 numbers but it could match the SVG
> width (also not in the interface)
>
> * The text of the cue:
> if the SVG animation contains text, it could be passed, if not, could be an
> empty string (or the content of a <desc> element) if required.
>
> The active flag: applicable
> The display state: applicable
>
> What I'm trying to say is that it seems very restrictive to limit the track
> element to pure text tracks. It disables interesting use cases (synchronized
> graphics overlay) while options to do it are there with SVG, already
> implemented in browsers.
>
>>
>> In my understanding, SVG has a complex DOM that goes far beyond what
>> TextTrack is capable of representing.
>
> I don't get this point. The definition of a TextTrack element should not
> care about the expressiveness of the language used to represent the text
> content as long as this language can be mapped to the TextTrack features: if
> it has graphics or not, if it can do bold/italic or not, if it can do bidi
> text or not ...
>
>> So, I think it's too rich a
>> format for the feature.
>
> "Oh I don't want your color TV, I just need a black-and-white one".
>
>>
>> Of course you can always throw any format at a HTML element.However,
>> if browsers don't support it, you can only deal with it through
>> JavaScript - so it's not a standardised feature and not really
>> relevant to the W3C.
>
> SVG is not any format. It's a W3C format. I think it's relevant.
>
> Cyril
>
> --
> Cyril Concolato
> Maître de Conférences/Associate Professor
> Groupe Multimedia/Multimedia Group
> Telecom ParisTech
> 46 rue Barrault
> 75 013 Paris, France
> http://concolato.wp.institut-telecom.fr/
>
Received on Thursday, 11 August 2011 10:35:50 UTC

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