W3C home > Mailing lists > Public > public-tt@w3.org > May 2013

Re: TTML Agenda for 15/05/13 - Proposed updates to charter

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Fri, 17 May 2013 13:51:47 +1000
Message-ID: <CAHp8n2mu_mD_2YsV8432Mmv9FLsLrdsOjdmEpai3Y=gjAHT6PQ@mail.gmail.com>
To: Pierre-Anthony Lemieux <pal@sandflow.com>
Cc: Michael Jordan <mijordan@adobe.com>, "public-tt@w3.org" <public-tt@w3.org>
TTML -> WebVTT conversion can happen outside the browser, so can be
done completely independently of your Web publishing pipeline.

The main advantage of publishing in WebVTT is that the captions in
such a page will work in browsers natively, even when JS is not
supported.

Also, it means that you don't have to write and maintain a JS TTML
parsing and rendering library - the rendering part is the difficult
part to implement and is typically the first one to break when your
video is rendered on a new device.

BTW: if you look at Firefox, the situation is identical, since Firefox
does not support WebVTT yet either (bug is in progress though). So, in
order to render WebVTT in Firefox, you need a WebVTT parsing and
rendering JS library (also called "polyfill"). There are several of
these around, but they age quickly and don't all work on mobile
devices. In contrast, e.g. the blink support of WebVTT makes it
available on all Chrome versions, including on mobile. For example, I
can play back http://html5videoguide.net/test/webvtt/test1.html on my
mobile phone with captions (using Chrome beta).

HTH,
Silvia.

On Fri, May 17, 2013 at 12:55 PM, Pierre-Anthony Lemieux
<pal@sandflow.com> wrote:
>> Yes, you can. You can do that with any format. However, that means
>> that JS supports the TTML format, not the browser.
>
> So shouldn't the following two processes roughly equivalent? If not, why?
>
> TTML document ---------> WebVTT document -----------> UA
> TTML document ----JS----> sequence of calls to TextTrack API
>
> Thanks,
>
> -- Pierre
>
> On Thu, May 16, 2013 at 7:38 PM, Silvia Pfeiffer
> <silviapfeiffer1@gmail.com> wrote:
>> On Fri, May 17, 2013 at 12:35 PM, Pierre-Anthony Lemieux
>> <pal@sandflow.com> wrote:
>>> Hi Silvia,
>>>
>>>> Yes... but that is unrelated to having TTML support in the browser.
>>>
>>> Well, if JS can create cues interactively, can't JS take a TTML
>>> document and, using the API, turn it into something that the browser
>>> will render?
>>
>> Yes, you can. You can do that with any format. However, that means
>> that JS supports the TTML format, not the browser.
>>
>> Regards,
>> Silvia.
Received on Friday, 17 May 2013 03:52:38 UTC

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