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RE: IMSCvNEXT kick-off + FPWD + liaisons

From: Michael Dolan <mike@dolan.tv>
Date: Mon, 2 Oct 2017 20:46:01 +0000
To: Pierre-Anthony Lemieux <pal@sandflow.com>, "public-tt@w3.org" <public-tt@w3.org>
Message-ID: <CY4PR10MB151092C17E3C2C803A31C1A9B47D0@CY4PR10MB1510.namprd10.prod.outlook.com>

Thanks for the quick work. I have a couple concerns about backwards compatibility with IMSC1.0.1.

Given the W3C practice of copying provisions in version N rather than normatively referencing version N-1, the opportunity for incompatibility is pretty moderate.  So, changing all references from TTML1 to TTML2 is a pretty risky thing to do in a new profile where we intend that it be compatible with version N-1, specifically such that IMSCvNext rendering results in the same output as from IMSC1.0.1.  Unless there is a conscious intent to extend a TTML1 feature in TTML2 it would be a lot safer to reference TTML1 for all the features found in IMSC1.0.1 and only reference TTML2 for new features or features that were intentionally extended in a backwards compatible manner.

Why is #image (from SMPTE namespace) deprecated?

The inclusion of #textShadow may enable one or two text attribute deprecations. When defining IMSC1 we did an alternative "best fit" for 708 requirements using some other text attributes for what textShadow can do.  I'll study this "soon" and make a proposal. It's probably not very likely that the alternatives were actually used.


-----Original Message-----
From: Pierre-Anthony Lemieux [mailto:pal@sandflow.com] 
Sent: Monday, October 2, 2017 9:02 AM
To: public-tt@w3.org
Subject: IMSCvNEXT kick-off + FPWD + liaisons

Good morning/evening,

I have pushed an initial Editor's Draft of IMSCvNEXT under the IMSCvNEXT branch [1].

[1] https://github.com/w3c/imsc/tree/IMSCvNEXT

The specification can be viewed at [2].

[2] https://rawgit.com/w3c/imsc/IMSCvNEXT/imsc1/spec/ttml-ww-profiles.html

The ED is based on the current requirements document [3].

[3] https://w3c.github.io/imsc-vnext-reqs/

As described at [3], IMSCvNEXT is intended to retain the scope of
IMSC1 while adding the minimal set of features necessary to support current practices for worldwide subtitling and captioning delivery.
>From a high-level, it looks like the bulk of the IMSCvNEXT
improvements will center around Japanese language, HDR and stereoscopic support.

As discussed during our last telecon, I suggest publishing a FPWD this week or next week and informing external organizations that the work has started.


-- Pierre

P.S.: It would be good to settle on a version number promptly, lest some folks call it vNEXT forever.

Received on Monday, 2 October 2017 20:46:28 UTC

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