Accessibility/Video a11y Study08: Difference between revisions

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Revision as of 03:20, 6 February 2009

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added extra paragraph on "raw text" format
(added extra paragraph on "raw text" format)
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Seeing the number of text categories identified above, it would make sense to have only one time-aligned text file format that can produce them all and is flexible enough to allow even further new time-aligned text ideas to be realised.
Seeing the number of text categories identified above, it would make sense to have only one time-aligned text file format that can produce them all and is flexible enough to allow even further new time-aligned text ideas to be realised.


Of all the formats that were analysed, DFXP is the most flexible format and is capable of producing multiple categories. It still needs to be determined, whether it would be possible for all of the given categories to be supported by DFXP, since DFXP is developed as an exchange format for subtitles and captions in particular. In any case, DFXP is not optimal for a Web-based time-aligned text format, since it redefines a lot of HTML, SMIL and CSS constructs, rather than re-using existing HTML, javascript and CSS. The re-definition was necessary because DFXP was developed as a generic format for time-aligned text, that needs to work in any situation, including outside the Web. However, for purposes of the Web (and for many Web-capable media players), reuse of HTML, CSS and javascript would lead to a format for which it would be much easier to provide implementations.
Another way to think about this is that the Web browser will only want to deal with one representation for time-aligned text. All formats should map to this representation. In this respect it is similar to defining a "raw" format for time-aligned text similar to how PCM is raw audio and RGB raw video. We can either invent a new format or pick up an existing format as this raw text format.


An idea for such a format is being discussed in the Xiph community. It runs under the name of TDHT (timed divs in HTML). A simple example file looks like this:
Of all the formats that were analysed, DFXP is the most flexible format and is capable of representing multiple categories. It still needs to be determined, whether it would be possible for all of the given categories to be supported by DFXP, since DFXP is developed as an exchange format for subtitles and captions in particular. In any case, DFXP is not optimal for a Web-based time-aligned text format, since it redefines a lot of HTML, SMIL and CSS constructs, rather than re-using existing HTML, javascript and CSS. The re-definition was necessary because DFXP was developed as a generic format for time-aligned text, that needs to work in any situation, including outside the Web. However, for purposes of the Web (and for many Web-capable media players), reuse of HTML, CSS and javascript would lead to a format for which it would be much easier to provide implementations.
 
An idea for such a format is being discussed in the Xiph community. It runs under the name of TDHT (Timed Divs in HTML). A simple example file looks like this:


<pre>
<pre>
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