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IMSCvNEXT + CSS styling was: TTML2 wide review comment: styling

From: Pierre-Anthony Lemieux <pal@sandflow.com>
Date: Sun, 1 Oct 2017 15:24:26 -0700
Message-ID: <CAF_7JxCoGcCQDgxid3wpPmcihC_iHcvobrc7=oOETPEj_Xv-mQ@mail.gmail.com>
To: David Ronca <dronca@netflix.com>, David Singer <singer@apple.com>
Cc: Timed Text Working Group <public-tt@w3.org>
Hi David and David et al.,

My experience with implementing imscJS [1] has been that the mapping
from IMSC1 to CSS was mostly straightforward and accurate, with the
exception of two features that are not available natively in CSS but
were deemed critical to captions: linePadding and multiRowAlign.

[1] https://github.com/sandflow/imscJS

In my mind, IMSCvNEXT should follow a similar pattern: mapping to
HTML/CSS should be straightforward and accurate, with the exception of
features that are essential to current subtitling/captioning
practices, but not yet available in CSS. For such features, a fallback
should be specified, and UA vendors should be encourages to support
the feature in the future.

Best,

-- Pierre

On Sat, Sep 30, 2017 at 6:01 PM, David Ronca <dronca@netflix.com> wrote:
>> Please consider adopting CSS as-is, without embellishment or improvement.
>
> CSS is beyond the scope of TTML2, and would be a requirement for TTMLvNext.
> Once of the deliverables for IMSCvNext will be a node.js  TTML->CSS
> transform implementation that will preserve as much of the TTML styling as
> possible.  This will simplify IMSCvNext rendering for HTML clients.
>
> On Sat, Sep 30, 2017 at 5:49 PM, David Singer <singer@apple.com> wrote:
>>
>> The styling model used in TTML2 is not CSS and is not processable by a
>> processor/rendering-engine designed to support HTML/CSS.  This leads to
>> complex ‘come from’ process deep in rendering engines, where the behavior
>> has to be dependent on whether the text ‘came from’ an HTML/CSS context or a
>> TTML context.
>>
>> Please consider adopting CSS as-is, without embellishment or improvement.
>>
>> David Singer
>> Manager, Software Standards, Apple Inc.
>>
>>
>
Received on Sunday, 1 October 2017 22:25:10 UTC

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