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<initial> vs inherited

From: Pierre-Anthony Lemieux <pal@sandflow.com>
Date: Tue, 2 Feb 2016 11:28:53 -0800
Message-ID: <CAF_7JxCUGHs=2ygp5HbqBESps2mHNfYfCvFaO6_pLYT4cFQRSQ@mail.gmail.com>
To: Glenn Adams <glenn@skynav.com>
Cc: Dae Kim <dakim@netflix.com>, Nigel Megitt <nigel.megitt@bbc.co.uk>, TTWG <public-tt@w3.org>
Hi Glenn et al.,

>Perhaps we need to review
> uninheritable properties in TTML2 to determine if we need to upgrade them to
> inheritable,

I like the idea of having a single mechanism for setting an initial
value for properties, i.e. avoid having to set a property explicitly
throughout the document.

Expanding inheritance (instead of introducing a new <initial> element)
seems promising, and intuitive.

> though doing so will require careful consideration of
> interoperability with TTML1 behavior.

I see two scenarios:

- an author wishes to create a document that conforms to both TTML1
and TTML2, in which case the author should set the property explicitly
throughout the document -- this is always safe.

- an author wishes to target only TTML2 processors, in which the
author can rely on the expanded inheritance rules

Are there other scenarios?

Best,

-- Pierre

On Fri, Jan 29, 2016 at 9:33 AM, Glenn Adams <glenn@skynav.com> wrote:
>
>
> On Fri, Jan 29, 2016 at 10:26 AM, Pierre-Anthony Lemieux <pal@sandflow.com>
> wrote:
>>
>> Hi Glenn,
>>
>> > This could also be done in other ways, such as by specifying these
>> > properties on the tt element,
>> > from which all inheritance would occur (in TTML2); however, that
>> > wouldn't work for properties
>> > that don't inherit, like tts:showBackground, etc.
>>
>> Why doesn't tts:showBackground inherit?
>
>
> It was originally defined on region in TTML1, which has no way for a region
> to inherit. However, we are adding root element inheritance in TTML2 (e.g.,
> from tt to head to layout to region). Perhaps we need to review
> uninheritable properties in TTML2 to determine if we need to upgrade them to
> inheritable, though doing so will require careful consideration of
> interoperability with TTML1 behavior.
>
>>
>>
>> Thanks,
>>
>> -- Pierre
>>
>> On Fri, Jan 29, 2016 at 9:11 AM, Glenn Adams <glenn@skynav.com> wrote:
>> > I can provide some respond to this.
>> >
>> > On Fri, Jan 29, 2016 at 8:14 AM, Pierre-Anthony Lemieux
>> > <pal@sandflow.com>
>> > wrote:
>> >>
>> >> Hi Dae,
>> >>
>> >> > initial
>> >>
>> >> How does Netflix plan to use <initial>?
>> >
>> >
>> > The TTT tools already support the initial element with the ttml2 model,
>> > and
>> > has found it to be very useful in specifying a variety of non-default,
>> > global style settings, such as default color and font related
>> > properties,
>> > etc.
>> >
>> > For example, the CAP2TT tool in TTT specifies a test configuration file
>> > that
>> > specifies a template for generating TTML2 output files in which is
>> > specified
>> > the following:
>> >
>> > <initial tts:fontSize="4vh"/>
>> > <initial tts:lineHeight="5vh"/>
>> > <initial tts:showBackground="whenActive"/>
>> >
>> > Here, initial is used to alter the default initial value. This could
>> > also be
>> > done in other ways, such as by specifying these properties on the tt
>> > element, from which all inheritance would occur (in TTML2); however,
>> > that
>> > wouldn't work for properties that don't inherit, like
>> > tts:showBackground,
>> > etc.
>> >
>> > Note that be using initial to specify an explicit tts:lineHeight, then
>> > there
>> > is no possibility of using the default initial value of 'normal' (which
>> > has
>> > been a problem with IMSC content).
>> >
>> > It is also useful for redefining the default initial value of
>> > tts:backgroundColor and resolving the platform dependent default initial
>> > value of tts:color.
>> >
>> >
>> >>
>> >>
Received on Tuesday, 2 February 2016 19:29:41 UTC

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