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Re: [media] Moving forward with captions / subtitles

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Tue, 16 Feb 2010 08:56:08 +1100
Message-ID: <2c0e02831002151356p44e0dcf0i8c5a05c57376035@mail.gmail.com>
To: Philip Jägenstedt <philipj@opera.com>
Cc: Eric Carlson <eric.carlson@apple.com>, HTML Accessibility Task Force <public-html-a11y@w3.org>
Hi Philip,

On Tue, Feb 16, 2010 at 12:04 AM, Philip Jägenstedt <philipj@opera.com> wrote:
> On Mon, 15 Feb 2010 19:29:48 +0800, Silvia Pfeiffer
> <silviapfeiffer1@gmail.com> wrote:
>
>> On Mon, Feb 15, 2010 at 6:06 PM, Philip Jägenstedt <philipj@opera.com>
>> wrote:
>>>
>>> On Mon, 15 Feb 2010 14:41:53 +0800, Silvia Pfeiffer
>>> <silviapfeiffer1@gmail.com> wrote:
>>>
>>> We've agreed on the basics for a long time, this is all about finding the
>>> appropriate markup/structure to express it, isn't it? I find my
>>> <track><source> suggestion confusing because <track> actually contains
>>> many
>>> tracks. Also, it makes the nesting mandatory, as <source> cannot be given
>>> as
>>> a direct child to <audio>/<video> as that would conflict with the
>>> resource
>>> selection algorithm. <trackgroup><track> is intended to address both of
>>> these problems.
>>
>> Oh, I didn't believe we would use <source> as the top-level, but it
>> would continue to be track.
>>
>> So, it would be either:
>>
>> <track role="SUB">
>>  <source src="subtitles.en.srt" lang="en">
>>  <source src="subtitles.sv.srt" lang="sv">
>>  <source src="subtitles.fr.srt" lang="fr">
>>  <source src="subtitles.zh.srt" lang="zh">
>> </track>
>> <track role="captions">
>>  <source src="captions.en.srt" lang="en">
>>  <source src="captions.sv.srt" lang="sv">
>>  <source src="captions.fr.srt" lang="fr">
>>  <source src="captions.zh.srt" lang="zh">
>> </track>
>>
>> when we want just one of the sources be chosen as the subtitle track.
>>
>> Or it would be:
>>
>> <track src="caption.en.srt" lang="en" role="CC">
>> <track src="subtitles.sv.srt" lang="sv" role="SUB">
>> <track src="subtitles.fr.srt" lang="fr" role="SUB">
>> <track src="subtitles.zh.srt" lang="zh" role="SUB">
>>
>> if they were all independent and possible to be activated in parallel,
>> just like the grouped tracks above can be active in parallel.
>
> Regardless of the element names, I think that if a minimized form (where the
> inner element is omitted) is allowed it should result in 4 mutually
> exclusive tracks, as this is quite surely the most common case.


I'm not sure what is the most common use case and maybe Geoff as a
practician can help here.

Is it more common to have a list of alternative text tracks (probably
subtitle tracks) on a video, or is it more common to have a mix of
text tracks (probably of different roles, CC, SUB, TAD, etc) that can
potentially be active together on a video.

We could, of course, add in the "active" attribute that we also have
in the JavaScript API and make selective tracks active just like we do
it with multitrack files:

<track src="caption.en.srt" lang="en" role="CC" active="true">
<track src="subtitles.sv.srt" lang="sv" role="SUB" active="true">
<track src="subtitles.fr.srt" lang="fr" role="SUB" active="false">
<track src="subtitles.zh.srt" lang="zh" role="SUB" active="false">

Then we do indeed replicate the multitrack structure of files.


> Since we all seem to be at least somewhat confused, here's a "common" and
> "complex" case expressed in both <track><source> and <trackgroup><track>
> markup. <track> in both forms clearly does *not* mean the same thing. Draw
> your own conclusions about which is better.

Excellent, very much appreciated!


> Simple case: two subtitle tracks in two different languages:
>
> In <track><source> markup:
>
> <video src="video.ogv">
>  <track role="SUB">
>    <source src="subs.en.srt" srclang="en">
>    <source src="subs.sv.srt" srclang="sv">
>  </track>
> </video>
>
> In <trackgroup><track> markup:
>
> <video src="video.ogv">
>  <track src="subs.en.srt" role="SUB" srclang="en">
>  <track src="subs.sv.srt" role="SUB" srclang="sv">
> </video>
>
> <trackgroup> is omitted because it is only needed when some tracks can be
> enabled in parallel. If one doesn't like typing role="SUB" twice one can use
> <trackgroup role="SUB">. In practice I think role="" will simply be omitted
> in simple cases like this, if the selection algorithm we define allows it.
>
>
>
> Complex case: two subtitle tracks and two caption tracks in two different
> languages:
>
> In <track><source> markup:
>
> <video src="video.ogv">
>  <track role="SUB">
>    <source src="subs.en.srt" srclang="en">
>    <source src="subs.sv.srt" srclang="sv">
>  </track>
>  <track role="CC">
>    <source src="cc.en.srt" srclang="en">
>    <source src="cc.sv.srt" srclang="sv">
>  </track>
> </video>
>
> In <trackgroup><track> markup:
>
> <video src="video.ogv">
>  <trackgroup role="SUB">
>    <track src="subs.en.srt" srclang="en">
>    <track src="subs.sv.srt" srclang="sv">
>  </trackgroup>
>  <trackgroup role="CC">
>    <track src="cc.en.srt" srclang="en">
>    <track src="cc.sv.srt" srclang="sv">
>  </trackgroup>
> </video>

Just like Geoff, I am wondering in this case whether this means you
either activate all the subtitles together or you activate all the
captions together. Since <trackgroup> is about enabling tracks in
parallel, this is what this would mean to me, right? And each
trackgroup against each other is exclusive, i.e. in this example I can
only either have subtitles or captions active, right?

Cheers,
Silvia.
Received on Monday, 15 February 2010 21:57:01 GMT

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