Re: Proposed extension to HTML5.1 for rollup captions

On Thu, Feb 21, 2013 at 7:23 PM, Silvia Pfeiffer
<silviapfeiffer1@gmail.com>wrote:

> Hi Glenn,
>
> On Thu, Feb 21, 2013 at 9:52 AM, Glenn Adams <glenn@skynav.com> wrote:
>
>>
>> On Wed, Feb 20, 2013 at 1:46 PM, Travis Leithead <
>> travis.leithead@microsoft.com> wrote:
>>
>>> > From: Silvia Pfeiffer [mailto:silviapfeiffer1@gmail.com]
>>> >
>>> > I'm looking for feedback on this feature here. If there are no
>>> objections
>>> > and sufficient support for these features, I suggest adding them to the
>>> > HTML5.1 specification.
>>>
>>> I'm very cautious about immediately merging this feature back into
>>> HTML5.1. I believe the best course of action is to keep this feature
>>> separate from the HTML5.1 spec (as a stand-alone document) as it allows
>>> easier review, as well as time to get consensus and develop the proposal
>>> based on feedback.
>>>
>>> Given that there is some time elapsed between now and when you can get
>>> sufficient support, then I don't object to merging it in. I would prefer to
>>> have at least a month or two to have time to gather all the right people
>>> together, perform the review, summarize and submit (and have time for you
>>> to incorporate any feedback).
>>>
>>> Finally, just a quick "thank you" for putting this together. I really
>>> like that extension specs are starting to be developed and I want to
>>> encourage folks to continue to submit these and get them started as
>>> reviewable documents.
>>>
>>
>> A few questions of clarification:
>>
>>    - does this rollup caption extension depend on
>>    https://dvcs.w3.org/hg/text-tracks/raw-file/default/608toVTT/region.html? if the answer is yes, then these TextTrackRegion interface extensions
>>    need to be renamed to WebVTTTextTrackRegion or otherwise made more generic
>>    to accommodate use of TTML instead of WebVTT
>>
>>
> No, they don't depend on WebVTT. It's a generic concept that builds on
> CEA708 windows and should thus similarly be able to present TTML rollup
> captions.
>
>
>>
>>    - does the mechanisms defined as extensions to the current HTML5
>>    TextTrack and related interface types take into account use of TTML instead
>>    of WebVTT? if the answer is no, then it should be reviewed and modified as
>>    needed to permit use of TTML as well, or at least support future
>>    integration with TTML
>>
>>
> Yes, it does just as much as TextTrackCue also permits use of TTML. I
> actually mentioned that in my email, but maybe not explicitly enough.
>
>
>>
>> Overall, we need to keep in mind that TTML will be used by commercial
>> video content providers for captioning HTML5 media elements,
>>
>

On a somewhat unrelated side note: while the industry is starting to use
TTML, only IE10 has released basic support for it in <track>. In contrast,
all browsers are implementing support for WebVTT (including IE10). Since
it's explicitly stated that TTML is created for *the purpose of interchange
among authoring systems*, while WebVTT is created for rendering in browsers,
it may be worthwhile to start creating a mapping between TTML and WebVTT.
I'd be happy to help.

Since the WebVTT extension that we are pursuing in the Community Group will
introduce means for authoring rollup captions in WebVTT, and the
TextTrackRegion provides the rendering means in the browser, the region
feature should fill the gaps that previously existed for the FCC required
caption features and thus for TTML conversion.

Regards,
Silvia.