[72 hours] Issue 47 (video captions/subtitles) -- chairs proposed solution

[Markus Gylling]

This is the proposed solution to issue 47 [1]. Deadline for objections: 08:00 UTC Friday April 22

After (as decided in autumn Adobe F2F) waiting as long as possible for this issue to settle at the W3C side, the chairs believe that it would be premature to mandate a single format for captions/subtitles in EPUB3. We propose to defer any possible single-format restriction to a later revision.

As a consequence of this, the TTML media type (application/ttml+xml) and the WebVTT media type (text/vtt) are both made Core Media Types in order to allow them to be used in content without the provision of fallbacks.

[1] http://code.google.com/p/epub-revision/issues/detail?id=47

[Peter Sorotokin]

What are the requirements on the publication? What are the requirements on
the Reading System?

Peter

[Daniel Weck]

The way I read it:

* Publications that include video captions/subtitles must use the TTML
or the WebVTT format. A given Publication may use both formats.
* Reading Systems should (must?) support both TTML and WebVTT formats.

Am I right ?
Daniel

Daniel Weck
danie...@gmail.com

[Geoff Freed]

I think Daniel is correct on the first point.  On the second point, it sounds like they *should* support both.  I’d be in favor of *must* but I wonder how practical that would be for reading-system vendors.

Geoff/NCAM

[Peter Sorotokin]

Hmm, I’d like to know exactly what we are agreeing to.

I would like a clarification for shoulds and musts.

I would like to know if it is a requirement to provide captions for video.

And I need to see what is the normative reference for WebVTT.

Peter

[Daniel Weck]

On Tue, Apr 19, 2011 at 8:39 PM, Peter Sorotokin <psor...@adobe.com> wrote:
> And I need to see what is the normative reference for WebVTT.

http://www.whatwg.org/specs/web-apps/current-work/multipage/video.html#webvtt-0

[Markus Gylling]

Sorry to be unclear folks, we won't deny we rushed this one out the door, so missed specifying the suggested RS requirements.  

The intent was to say:

* TTML and WebVTT are made Core Media Types, which means that they can be used in content without fallbacks

* Reading Systems [that support video] must support at least one of these

I would like to know if it is a requirement to provide captions for video. 

No, and since there is no such requirement in HTML5 either, we don't think it is necessary to talk about this in the EPUB spec. 

 

And I need to see what is the normative reference for WebVTT.

Right - as pointed out, the document lives at whatwg.org; I am not updated on whether or not W3C is planning to "adopt" this - perhaps someone else can fill in on that.

Feel free to suggest alternate solutions.

/markus

[Geoff Freed]

While TTML is a fully baked W3C recommendation and is in use today mostly for Flash and Silverlight captioning, WebVTT is still in development.  It’s being assembled largely by Google without any formal working-group structure, but there has been discussion about the W3C possibly taking over its formal development at some point.  As far as I know, however, there is no timeline for this.  Even so, WebVTT is something to keep an eye on because it *may* wind up being part of the WHAT-WG version of HTML even if it isn’t simultaneously part of the W3C version of HTML5.

On second thought... naming TTML as a core media type is a good idea, but I’m waffling on WebVTT.

Geoff/NCAM

On 4/20/11 4:23 AM, "Markus Gylling" <markus....@gmail.com> wrote:

Sorry to be unclear folks, we won't deny we rushed this one out the door, so missed specifying the suggested RS requirements.  

The intent was to say:

* TTML and WebVTT are made Core Media Types, which means that they can be used in content without fallbacks
* Reading Systems [that support video] must support at least one of these

I would like to know if it is a requirement to provide captions for video.

No, and since there is no such requirement in HTML5 either, we don't think it is necessary to talk about this in the EPUB spec.

 

And I need to see what is the normative reference for WebVTT.

Right - as pointed out, the document lives at whatwg.org <http://whatwg.org> ; I am not updated on whether or not W3C is planning to "adopt" this - perhaps someone else can fill in on that.

Feel free to suggest alternate solutions.

/markus



On Apr 19, 2011, at 9:39 PM, Peter Sorotokin wrote:

Hmm, I’d like to know exactly what we are agreeing to.

I would like a clarification for shoulds and musts.

I would like to know if it is a requirement to provide captions for video.

And I need to see what is the normative reference for WebVTT.

Peter


On 4/19/11 11:37 AM, "Geoff Freed" <geoff...@wgbh.org <x-msg://440/geoff...@wgbh.org> > wrote:

I think Daniel is correct on the first point.  On the second point, it sounds like they *should* support both.  I’d be in favor of *must* but I wonder how practical that would be for reading-system vendors.

Geoff/NCAM



On 4/19/11 1:10 PM, "Daniel Weck" <danie...@gmail.com <x-msg://440/danie...@gmail.com> > wrote:

The way I read it:

* Publications that include video captions/subtitles must use the TTML
or the WebVTT format. A given Publication may use both formats.
* Reading Systems should (must?) support both TTML and WebVTT formats.

Am I right ?
Daniel

On 19 Apr 2011, at 17:17, Peter Sorotokin wrote:

> What are the requirements on the publication? What are the
> requirements on
> the Reading System?
>
> Peter
>

> On 4/19/11 12:45 AM, "Markus Gylling" <markus....@gmail.com <x-msg://440/markus....@gmail.com> >

> wrote:
>
>> This is the proposed solution to issue 47 [1]. Deadline for
>> objections: 08:00
>> UTC Friday April 22
>>
>> After (as decided in autumn Adobe F2F) waiting as long as possible
>> for this
>> issue to settle at the W3C side, the chairs believe that it would
>> be premature
>> to mandate a single format for captions/subtitles in EPUB3. We
>> propose to
>> defer any possible single-format restriction to a later revision.
>>
>> As a consequence of this, the TTML media type (application/ttml
>> +xml) and the
>> WebVTT media type (text/vtt) are both made Core Media Types in
>> order to allow
>> them to be used in content without the provision of fallbacks.
>>
>> [1] http://code.google.com/p/epub-revision/issues/detail?id=47
>

Daniel Weck

danie...@gmail.com <x-msg://440/danie...@gmail.com>

[Peter Sorotokin]

I am not sure what’s the status of this is? This needs to be resubmitted, I think.

I just want to make sure that 72 hour clock is not ticking on this one.

Peter

[Innovimax SARL]

I would like to add to this discussion, that while TTML is a W3C REC (I voted against as an AC Rep), it doesn't have the quality of a REC and furthermore it requires many specific development (their is substantial incompatibilities with all the CSS stack and many introduced values are poorly defined)

So I wouldn't go for requiring TTML AT ALL, because of that

I could give more technical details if necessary

Best regards,

Mohamed

--
Innovimax SARL
Consulting, Training & XML Development
9, impasse des Orteaux
75020 Paris
Tel : +33 9 52 475787
Fax : +33 1 4356 1746
http://www.innovimax.fr
RCS Paris 488.018.631
SARL au capital de 10.000 €

[Markus Gylling]

Yes, the proposal needs to be revised. Per comments in this thread, we have enough evidence that we do not have consensus on the proposed solution. Also as a FYI, below are two comments provided by members of the html accessibility task force, by way of Oedipus.

--------------

One point worth sharing is that a profile of TTML has emerged from the

Society of Motion Picture and Television engineers (SMPTE), that has added a

few extra 'bits' (mostly around meta-data as I understand it) to the TTML

base. (This is in keeping with TTML's design as being extensible) The

SMPTE-TT spec is available for download free of charge.  You can download

the spec at:

http://store.smpte.org/product-p/st%202052-1-2010.htm

Given that this will likely be what "Hollywood" will be outputting natively,

it might be worth a look by the epub group as well. FWIW.

--------------

I think HTML5 will have WebVTT as the baseline codec for captions, but
allow for other formats to be supported, too. That's slightly
different to what you have with both WebVTT and TTML being supported
formats. There is no way that we will get TTML support by all
browsers.

I think we will eventually create a WebVTT WG at the W3C. For now, the
spec is here: http://www.whatwg.org/specs/web-apps/current-work/webvtt.html

--------------

[Dave Makower]

I think it's premature (in terms of the lifecycle of these formats) and very late (in terms of the stage we're at in the EPUB 3.0 process) to be proposing either of these formats as RS requirements.  We can't promise to support these (especially not to support both) in the near future.

-- Dave

-- 

Dave Makower

Apple, Inc.

1 Infinite Loop, M/S: 39-1ME

Cupertino, CA  95014

phone: (408) 974-2640

email: dav...@apple.com