ttp:version is not required for processor capability signaling

• From: Pierre-Anthony Lemieux <pal@sandflow.com>
• Date: Fri, 10 Nov 2017 16:30:01 -0800
• To: public-tt@w3.org
• Message-ID: <CAF_7JxAY-g6JGfM0bRGGvN6s3BXDL=-_meWCALsT0stgnjCFog@mail.gmail.com>

Good morning/evening,

Following-up on our F2F, below is a discussion re: ttp:version should
not be used to signal processor requirements in TTML2, and can likely
be entirely removed.

1. The profiling vocabulary and semantics (#profile,
ttp:processorProfiles, ttp:contentProfiles...) allows the author to
precisely specify the capabilities needed to process the document,
removing the need for ttp:version to signal default profiles (Section
5.2.4.3). This would moot issue #435.

2. ttp:version currently overrides TTML1 processor behavior in absence
of both tts:origin and tts:position (Section 11.1.2). I found no
concrete requirements for such override, which can, in any case, (i)
be signaled using the #initial feature or (ii) be explicitly triggered
by specifying tts:position.

3. ttp:version is currently used to signal deprecation of offset-time
and clock-time forms when the governing time base is smpte (Section
12.3.1). Deprecation is not a prohibition, and can therefore be
accomplished without using ttp:version, i.e. a TTML1 document would
remain a valid TTML2 document if TTML2 simply deprecated these two
scenarios.

Best,

-- Pierre

Received on Saturday, 11 November 2017 00:30:46 UTC