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

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Wed, 10 Aug 2011 10:38:35 +1000
Message-ID: <CAHp8n2mT7ybK38RjDLfFqFc6-bEN=5sU-eZbAPc4BDpDn5L57A@mail.gmail.com>
To: Duncan Rowden <Duncan.Rowden@bbc.co.uk>
Cc: public-web-and-tv@w3.org
Hi Duncan,

I think what you are describing is highly interesting: you are
analysing how to overlay image maps onto video such that you can click
on regions and hyperlink to another Web resource. I believe this is
indeed still a challenge. It is possible to realise this using the
<track> element on <video> with a @kind=metadata and providing the
hyperlinks and their regions in a WebVTT file in some format, then
using JavaScript to render the clickable regions onto the video. This
could be done by rendering the video into a <canvas> and using image
maps on the resulting canvas images. Then all the image map related
functionality is available to the moving images, including CSS and you
could zoom into a region of the video upon the click. I'd be curious
about such an implementation and how it performs, actually.

I don't think you can do it without a <canvas> since the <map> tag
only applies to images and not video. We could consider requesting a
@usemap attribute on video and extending the use of <map> to <video>,
but we only get fixed regions clickable in this way, not dynamically
changeable over the duration of the video.

I wonder if instead it might be worth analysing if we can come up with
a <track> kind that allows overlaying hyperlinkable regions onto the


On Wed, Aug 10, 2011 at 2:13 AM, Duncan Rowden <Duncan.Rowden@bbc.co.uk> wrote:
> Hi All,
> As requested in Action-67(http://www.w3.org/2011/webtv/track/actions/67)
> I've looked into ISSUE-37 and whether it can already be done using existing
> techniques. In particular with reference to the <map> tag.
> In short the <map> tag allows a user-agent to define a clickable area on an
> image, which will take the user to a link, if one is defined. Allowing the
> map tag to be used in conjunction with the <video> tag would be a feasible
> proposition. This "video map" tag could consequently make the clickable area
> change the CSS of the video tag. This would allow the a clip property to be
> utilised and any required scaling could be performed then as well.
> Additionally if any animations are to be performed, this could be done using
> CSS3 animations at this time.
> The question I have is if it is sensible to have an href attribute for a
> “video map” solely to perform some javascript functionality, or whether
> specific scaling attributes should be defined?
> On a side note, I have noticed from using the CSS clip method on the <video>
> tag, that the video controls are cropped as well. If I’m not too mistaken
> this is highly undesirable, if not even a bug.
> ISSUE-37 Link:
> http://www.w3.org/2011/webtv/wiki/MPTF/MPTF_Discussions/ViewPort-Support
> Regards,
> Duncan
> __________________________
> Duncan Rowden
> Research Engineer, Research & Development
> BBC Future Media & Technology
> Room 2.30, Centre House, 56 Wood Lane, London W12 7SB
> E:         duncan.rowden@bbc.co.uk
> T:         +44 (0)3030 409560
> F:         +44 (0)2088 118815
> W:        http://www.bbc.co.uk/rd
> http://www.bbc.co.uk
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Received on Wednesday, 10 August 2011 00:39:22 UTC

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