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RE: Requirements for external text alternatives for audio/video

From: Sean Hayes <Sean.Hayes@microsoft.com>
Date: Fri, 26 Mar 2010 23:01:11 +0000
To: Eric Carlson <eric.carlson@apple.com>
CC: Silvia Pfeiffer <silviapfeiffer1@gmail.com>, Geoff Freed <geoff_freed@wgbh.org>, HTML Accessibility Task Force <public-html-a11y@w3.org>, Matt May <mattmay@adobe.com>, Philippe Le Hegaret <plh@w3.org>
Message-ID: <8DEFC0D8B72E054E97DC307774FE4B9119EFE94C@DB3EX14MBXC315.europe.corp.microsoft.com>
Fine.  The same behaviour could be allowed when rendering video to a canvas, that the rendered caption pixels could be read back.  

The encoded pixel data of an image however is not made available (e.g. PNG chunks, or text of an SVG image), and that is what I meant.

-----Original Message-----
From: Eric Carlson [mailto:eric.carlson@apple.com] 
Sent: Friday, March 26, 2010 10:37 PM
To: Sean Hayes
Cc: Silvia Pfeiffer; Geoff Freed; HTML Accessibility Task Force; Matt May; Philippe Le Hegaret
Subject: Re: Requirements for external text alternatives for audio/video


On Mar 26, 2010, at 3:13 PM, Sean Hayes wrote:

> I don't think any exposure of the caption text should be made to HTML. There is afaik no exposure to the pixels of an img, the samples of audio, or the frames of a video.
> 

  It is possible to draw an image or a frame of video into a <canvas> element. It is then possible to read the pixels back out of the canvas, but only if everything drawn into the canvas and the document that owns the canvas have the same origin[1].

eric


http://dev.w3.org/html5/spec/the-canvas-element.html#security-with-canvas-elements
Received on Friday, 26 March 2010 23:01:48 GMT

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