[whatwg] On the subtitle format for HTML5

Carlos Andrés Solís csolisr at gmail.com
Sat May 22 20:39:40 PDT 2010

Hello, I've been writing lately in the WHATWG and WebM mail-lists and would
like to hear your opinion on the following idea.

Imagine a hypothetical website that delivers videos with subtitles that can
be chosen by the user. And also imagine there is the possibility of
downloading a file with the video, along with either the chosen subtitle
tracks, or all of them at once. The problems on multiple tracks I have
already discussed in another thread; this one deals mainly with subtitle
formats. There is still an issue on which format should be used for
subtitling in HTML5. As you might know, there are basic subtitle formats
that are formed by timed plain text and little else (like SRT or the
proposed WebSRT), and there are full-blown subtitle formats that allow for
extreme formatting and typesetting (like Advanced SubStation Alpha). The
basic subtitles have the advantage of being easily editable by hand, but
sacrificing capabilities that advanced formats allow with the cost of
harder-to-understand syntax. It would be a shame to drop advanced subtitles
from the HTML5 specs, but it would be bothersome if everybody is forced to
use a complex-to-write format. So a middle ground could be handy: allowing
WebSRT for the simple tasks, and using another format for advanced
typesetting. To put an example, ASSA allows to modify the text font, size,
border, shadow, scale, rotation, position, and some other properties; it
also allows movement of text, text animation, karaoke, and even some
vectorial graphing. But all of that could be achieved with HTML5 programming
on top of the WebSRT format (or whichever gets chosen). This, of course,
causes a pair of problems.
* The first one is that there would be no tools to edit HTML5 subtitles
specifically, forcing to make a type of subset which would have to be
standardized, plus an editor to be able to create such subtitles without
having to learn how to create a full-blown website.
* The second one is that media players that wanted to use such subtitles
would be forced to ship an HTML5 decoder. Most media players are NOT web
browsers, though, or based on one either. The only exceptions I remember are
media players built on top of XUL, like Songbird or Nightingale. But players
like WMP, WinAmp, VLC, Xine family, GStreamer family or MPlayer family would
be left out, since they have no need (and no time) to plug in a web browser
in a program that hasn't needed it.

Any ideas or suggestions?
- Carlos Solís
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