Re: Inpute re: TTML2

Do you believe that any of your comments required addressing before going
to FPWD?

On Wed, Jan 28, 2015 at 11:37 PM, Pierre-Anthony Lemieux <pal@sandflow.com>
wrote:

> Good morning/evening,
>
> Below are potential topics of discussion in light of my initial review
> of the most recent TTML2 ED.
>
> A number of comments concern divergence between TTML2 ED, and SMPTE ST
> 428-7 and SMPTE-TT. It is entirely possible that the SMPTE
> specifications are in error. IMHO the world does not however need
> further divergence between timed text formats, so, at minimum, I
> recommend that TTWG communicate its decisions to SMPTE.
>
> Best,
>
> -- Pierre
>
> > Forced Display
>
> - the specification would benefit from a definition and example (see IMSC1)
> - how can a profile support Forced Display without having to implement
> the full conditional language?
>
> > image positioning
>
> smpte:backgroundImageHorizontal and smpte:backgroundImageVertical
> allow positioning of "the background image of a rendered area",
> including using percentages. Does TTML2 allow positioning of <image>
> within a region, other than using tts:displayAlign?
> tts:backgroundPosition applies only to non-content images.
>
> > ttp:mediaOffset
>
> The relationship between ttp:mediaOffset, root temporal extent,
> implicit duration of the body element, computed duration of the body
> element, body@start would benefit from a diagram.
>
> > """The ttp:mediaOffset attribute is used to specify the temporal offset
> between the begin time of the root temporal
> > extent and the begin time of a related media object when operating in a
> Media Time Base or a SMPTE Time Base."""
>
> A container typically controls the synchronization between audio,
> video and subtitles. Why not simply move the relative start time of
> the subtitle essence within the container instead of changing the
> subtitle essence itself?
>
> > [root temporal extent] The temporal extent (interval) defined by the
> temporal beginning and ending of a
> > document instance in relationship with some external application or
> presentation context.
>
> Why is the root temporal extent defined in relationship with some
> external application or presentation context? Isn't it intrinsically
> defined by the smallest and largest computed time value within the
> document?
>
> > In particular, the statement must identify the utilized or supported
> TTML vocabulary profile(s) as defined by 5.2 Profiles,
>
> Section 5.2 does not define "TTML vocabulary profile".
>
> > """if the ttp:contentProfiles attribute is specified using the all(...)
> function syntax or using no function syntax, i.e., as only a list of
> > designators, then the effective content profile is the combined profile
> specification set produced by combining the combined profile
> > specification sets of the designated profiles, where the mostRestrictive
> content profile combination method applies;"""
>
> What would be an example of the use of all(...) function syntax?
>
> > The tts:textEmphasis attribute is used to specify a style property that
> determines whether and how text emphasis marks are presented on affected
> content.
>
> What are "text emphasis marks"? A reference would be useful.
>
> > 10.2.3 tts:backgroundImage
>
> This seems to have a much narrower scope than smpte:backgroundImage.
> It would be good to rename to prevent confusion, or add a prominent
> warning.
>
> > tts:position
>
> what is the use case for tts:position?
>
> > tts:textCombine
>
> As far as I can tell this is substantially different than the HGroup
> feature in ST 428-7. Specifically, the horizontal text in ST 428-7 is
> not "combin[ed] into an em square of the surrounding vertical text,"
> but rather set horizontally with a font size selected by the author.
>
> > tts:textOrientation
>
> sidewaysRight/sidewaysLeft specify rotation of glyphs from horizontal
> scripts in vertical writing modes. The Rotate feature in ST 428-7 does
> not contain this limitation, but merely notes that "this is most
> commonly used to present special characters in a text string that is
> being displayed vertically."
>
> > tts:ipd
>
> tts:ipd does not allow negative spacing, as allowed by the Space
> feature in SMPTE ST 428-7.
>
>