Video is accessible when every person, no matter what limitations in language understanding, hearing, seeing, or other senses, can follow what is happening in a video and navigate it. Video accessibility is fundamentally about providing textual and other additional information about the video to help provide information in channels other than eyes and ears.
Captions and subtitles are only one type of accessibility features - there are also audio annotations for the blind, and many other text representations that are related. For years, people have been requesting a solution for Ogg content with subtitles/captions. So far, the main solution was to create a text file (e.g. a srt file) and load it together with the video file into a media player that was then able to do the subtitling ("soft subs"). Now that Firefox supports Ogg Theora/Vorbis out of the box, an encapsulated solution is required ("hard subs").
Silvia is working for Xiph and Mozilla on this and has recently proposed a generic mapping of "text codecs" into Ogg. This will encapsulate the W3C TimedText standard as well as your fansubber's typical formats.
5. Alternative
• Captions are an alternative to sign
language
• Textual audio annotations are an
alternative to audio
– Rendering via braille
– Rendering via screen-readers - possibly
mono on one ear only
7. Captions/Subtitles:
srt example
0
00:00:01,120 --> 00:00:04,520
1
00:00:05,000 --> 00:00:07,440
In most countries
on the continent
2
00:00:08,000 --> 00:00:12,720
There were princes,
they were absolute regimes,
8. How to link srt to <video>
• Ad-hoc: http://v2v.cc/~j/jquery.srt/
<script type=quot;text/javascriptquot; src=quot;jquery.jsquot;></script>
<script type=quot;text/javascriptquot;
src=quot;jquery.srt.jsquot;></script>
<video src=quot;http://example.com/video.ogvquot; id=quot;videoquot;
controls>
<div class=quot;srtquot;
data-video=quot;videoquot;
data-srt=quot;http://example.com/video.srtquot; />
14. Example ticker text
• AJAX XML ticker using .txt file
<div class=quot;messagequot;>
<a href=quot;http://www.javascriptkit.comquot; target=quot;_newquot;>JavaScript
Kit</a><br />Comprehensive JavaScript tutorials and over
400+ free scripts!
</div>
<div class=quot;messagequot;>
<a href=quot;http://www.codingforums.comquot;>Coding Forums
2</a><br />Web coding and development forums.
</div>
<div class=quot;messagequot;>
<a href=quot;http://www.cssdrive.comquot;>CSS
Drive</a><br/>Categorized CSS gallery and examples.
</div>
15. Example .trs file
<?xml version=quot;1.0quot; encoding=quot;ISO-8859-1quot;?>
<!DOCTYPE Trans SYSTEM quot;trans-14.dtdquot;>
<Trans scribe=quot;James Eaton-Leequot; audio_filename=quot;scl2007_eben_moglenquot; version=quot;9quot;
version_date=quot;070701quot; xml:lang=quot;enquot;>
<Topics>
<Topic id=quot;to1quot; desc=quot;The Global Software Industry in Transformation: After GPLv3quot;/>
</Topics>
<Speakers>
<Speaker id=quot;spk1quot; name=quot;Eben Moglenquot; check=quot;noquot; type=quot;malequot; dialect=quot;nativequot;
accent=quot;American Englishquot; scope=quot;globalquot;/>
</Speakers>
<Episode program=quot;quot; air_date=quot;26/07/2007quot;>
<Section type=quot;reportquot; startTime=quot;0quot; endTime=quot;4938.762quot; topic=quot;to1quot;>
<Turn startTime=quot;0quot; endTime=quot;146.632quot; speaker=quot;spk2quot; mode=quot;plannedquot; fidelity=quot;highquot;
channel=quot;studioquot;>
<Sync time=quot;0quot;/>
Good evening everybody, and welcome to the Scottish society for Computers and Law annual
lecture for 2007.
<Sync time=quot;14.574quot;/>
And it's I think a testament to the drawing power of our speaker this evening that we've got
such a great turnout and there's an enduring interest in the subject of course, and so we're
very very pleased to see not only lawyers, but real people as well.
<Sync time=quot;36.537quot;/>
16. And what about further text-
based functions?
• Active regions
• Chapter markers / Cue points
-> Hyperlinks
17. What is the best language for
text and hyperlinks on the
Web?
18. W3C Timed Text?
• DFXP: Distribution Format Exchange Profile
<tt xml:lang=quot;quot; xmlns=quot;http://www.w3.org/2006/10/ttaf1quot;>
<head>
<metadata/>
<styling/>
<layout/>
</head>
<body region=quot;subtitleAreaquot;>
<div>
<p xml:id=quot;subtitle1quot; begin=quot;0.76squot; end=quot;3.45squot;>It seems a
paradox, does it not,</p>
<p xml:id=quot;subtitle2quot; begin=quot;5.0squot; end=quot;10.0squot;>that the image
formed on<br/>the Retina should be inverted?</p>
</tt>
19. Why not just use HTML?
• CSS for styling
• Javascript for effects
• Proposal: TDHT - Timed Divs HTML
Body only has sequence of DIV tags
with start and end attributes
http://wiki.xiph.org/index.php/Timed_Divs
_HTML
20. Next Steps
• Build a collection of example files
• Implement SRT support
– Out-of-band
– In-line
• Implement TDHT support
• Detailed Specification
• Non-text codecs
• Content selection / adaptation
• Standardisation
