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Captions (was Re: Shifting gears for a second (was RE: Codecs for <video> and <audio>))

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Sat, 4 Jul 2009 12:41:00 +1000
Message-ID: <2c0e02830907031941o5286f335j7cc336fdfcfce6a6@mail.gmail.com>
To: Matthew Ratzloff <matt@builtfromsource.com>
Cc: public-html@w3.org
Hi Matthew,

Let's not invent yet another caption file format. There are already
plenty out there, amongst them srt and the new DFXP of the W3C Timed
Text working group. I think these are more than adequate for

Also, there have been a large number of proposals to link external
caption files to videos, amongst them:


Most of them look rather similar, so let's see what implementations
and experiments the browser vendors come up with. So far we have had a
set of javascript implementations of some of the proposals and general
javascript hacks (see e.g. the examples pointed out at


On Sat, Jul 4, 2009 at 11:26 AM, Matthew
Ratzloff<matt@builtfromsource.com> wrote:
> On Fri, Jul 3, 2009 at 2:39 AM, Silvia Pfeiffer <silviapfeiffer1@gmail.com>
> wrote:
>> 10 years ago I was mkaing the same arguments that you are. But now,
>> after having tried to push for time-aligned text inside audio-visual
>> files for so long, I have come to the conclusion that it is actually
>> easier to deal with separate files than with captions inside media
>> files. As external files, they are easier to edit, easier to share,
>> easier to access, easier to parse, easier to handle on a server (e.g.
>> in a database) and generally easier to manage.
> Agreed.  Perhaps this is naive, but something like the following seems
> sensible to me:
> <video src="videos/video.ogg" captions="videos/video_captions.xml"/>
> Where video_captions.xml could contain something like:
> <captions>
>   <caption lang="en-US" start="23" end="42" position="23,43">English
> caption</caption>
>   <caption lang="en-US" start="43" end="84">Another caption</caption>
>   <caption lang="fr-CA" start="23"
> end="42" position="23,43">Légende français</caption>
>   <caption lang="fr-CA" start="43" end="84">Une autre légende</caption>
> </captions>
> Instead of frames, @start and @end could also be specified as times.
>  @position is X and Y from top left, reminiscent of image map positioning.
>  @start and @end would be the only required attributes.
> For convenience, the captions element could exist within the video element
> as well instead of being referenced in another file.  Internal captions
> would also allow them to be scriptable via the DOM.
> -Matt
Received on Saturday, 4 July 2009 02:42:02 UTC

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