Re: [IMSC] Thoughts re: issue-312 -- itts:forcedDisplay

In this example, the conditional content would suffice, since there is no
layout interaction between the two regions.


On Sun, Jun 22, 2014 at 9:31 PM, Pierre-Anthony Lemieux <pal@sandflow.com>
wrote:

> Hi Glenn,
>
> Attached is an example inspired from an opening shot from The Muppets
> (2011) Blu-Ray.
>
> The forced subtitle is the translation of the "High School" sign. It
> appears when French is selected as the language, even if the user has
> not explicitly selected French subtitles, i.e. when 'forced mode' is
> true.
>
> The translation of the voiceover is not labeled 'forced', and thus
> shows up only when French subtitles are selected, i.e. 'forced mode'
> is false.
>
> Best,
>
> -- Pierre
>
> P.S.: in UVVU, 'forced mode'=='true' is called "Alternate Subtitling
> Presentation Mode" and 'forced mode'=='false' is called "Primary
> Subtitling Presentation Mode".
>
> On Sat, Jun 21, 2014 at 7:17 PM, Glenn Adams <glenn@skynav.com> wrote:
> > Could you point at or construct a real world example, i.e., images of
> what a
> > mixture of forced and non-forced content looks like depending on whether
> a
> > forced display parameter is true or false?
> >
> >
> > On Sat, Jun 21, 2014 at 6:56 PM, Pierre-Anthony Lemieux <
> pal@sandflow.com>
> > wrote:
> >>
> >> Hi Glenn,
> >>
> >> > why would one want it to occupy layout space if not selected?
> >> > that doesn't make any sense;
> >>
> >> The forced content would have been positioned with the non-forced
> >> content present. Simply removing the non-forced content from flow
> >> would potentially change the rendered position of the forced content.
> >>
> >> I will confirm this.
> >>
> >> Best,
> >>
> >> -- Pierre
> >>
> >> On Sat, Jun 21, 2014 at 5:50 PM, Glenn Adams <glenn@skynav.com> wrote:
> >> >
> >> > On Sat, Jun 21, 2014 at 6:43 PM, Pierre-Anthony Lemieux
> >> > <pal@sandflow.com>
> >> > wrote:
> >> >>
> >> >> Hi Glenn,
> >> >>
> >> >> Thanks for these initial thoughts.
> >> >>
> >> >> > 3. evaluating this sub-tree in a postorder traversal, prune
> elements
> >> >> > if they are not a content element, if they have a condition
> attribute
> >> >> > that evaluates to false,
> >> >>
> >> >> "Forced" does not remove the content element from layout and flow,
> but
> >> >> instead
> >> >> effectively sets the visibility to zero, like
> tts:visibility="hidden".
> >> >
> >> >
> >> > it should; why would one want it to occupy layout space if not
> selected?
> >> > that doesn't make any sense;
> >> >
> >> > i don't see how to handle conditional content and conditional
> >> > visibility; i
> >> > think the best you will get is the former
> >> >
> >> >>
> >> >>
> >> >> Best,
> >> >>
> >> >> -- Pierre
> >> >>
> >> >> On Sat, Jun 21, 2014 at 5:38 PM, Glenn Adams <glenn@skynav.com>
> wrote:
> >> >> >
> >> >> >
> >> >> > On Sat, Jun 21, 2014 at 6:07 PM, Pierre-Anthony Lemieux
> >> >> > <pal@sandflow.com>
> >> >> > wrote:
> >> >> >>
> >> >> >> > What do you mean by "application" in this context?
> >> >> >>
> >> >> >> The entity that is instructing the presentation processor to
> render
> >> >> >> the IMSC document.
> >> >> >>
> >> >> >> > I also don't know what parameter means in this context,
> >> >> >> > e.g., what does it mean vis-a-vis a TTML parameter, i.e.,
> >> >> >> > an attribute expressing a TTML parameter.
> >> >> >>
> >> >> >> It is not a TTML parameter, as in a ttp:*, but instead a state
> >> >> >> variable passed to the presentation processor instructing it to
> >> >> >> render
> >> >> >> or not non-forced content, like a function argument in a
> procedural
> >> >> >> language.
> >> >> >>
> >> >> >> > I am opposed to a one-off solution to a special case of the
> >> >> >> > conditional
> >> >> >> >  content problem. And the forcedDisplay feature is exactly such
> a
> >> >> >> > special case.
> >> >> >>
> >> >> >> Can you think of a generic solution that would reduce to a single
> >> >> >> attribute controlling the rendering of forced content? If so, we
> >> >> >> could
> >> >> >> consider using it in IMSC.
> >> >> >
> >> >> >
> >> >> > I haven't given it much thought, but if we were to introduce as the
> >> >> > general
> >> >> > mechanism a new element type:
> >> >> >
> >> >> > <tt:switch condition="expression">
> >> >> > ... content elements ...
> >> >> > </tt:switch>
> >> >> >
> >> >> > then we could also, or as an alternative, introduce an attribute
> >> >> > @condition
> >> >> > on content element vocabulary, e.g.,
> >> >> >
> >> >> > <div condition="expression"/>
> >> >> >
> >> >> > where expression uses a simple expression language such as media
> >> >> > queries
> >> >> > level 4 [1] or a derivative.
> >> >> >
> >> >> > [1] http://dev.w3.org/csswg/mediaqueries4/
> >> >> >
> >> >> > For example,
> >> >> >
> >> >> > <p condition="(forced)"/>
> >> >> >
> >> >> > <p condition="not (forced)"/>
> >> >> >
> >> >> > <p condition="(locale: en)"/>
> >> >> >
> >> >> > <p condition="not (locale: en)"/>
> >> >> >
> >> >> > <p condition="(forced) or not (locale: en)"/>
> >> >> >
> >> >> > ...
> >> >> >
> >> >> > Where the semantics of @condition is essentially changing step 3 of
> >> >> > 9.3.3
> >> >> > [construct intermediate document] to read essentially as follows:
> >> >> >
> >> >> > 3. evaluating this sub-tree in a postorder traversal, prune
> elements
> >> >> > if
> >> >> > they
> >> >> > are not a content element, if they have a condition attribute that
> >> >> > evaluates
> >> >> > to false, if they are temporally inactive, if they are empty, or if
> >> >> > they
> >> >> > aren't associated with region R according to the [associate region]
> >> >> > procedure;
> >> >> >
> >> >> >>
> >> >> >>
> >> >> >> Thanks,
> >> >> >>
> >> >> >> -- Pierre
> >> >> >>
> >> >> >> On Fri, Jun 20, 2014 at 10:56 PM, Glenn Adams <glenn@skynav.com>
> >> >> >> wrote:
> >> >> >> >
> >> >> >> > On Fri, Jun 20, 2014 at 10:33 PM, Pierre-Anthony Lemieux
> >> >> >> > <pal@sandflow.com>
> >> >> >> > wrote:
> >> >> >> >>
> >> >> >> >> Hi Glenn,
> >> >> >> >>
> >> >> >> >> Thanks for the feedback.
> >> >> >> >>
> >> >> >> >> > no, [forcedDisplayModeParameter] should not be a parameter,
> in
> >> >> >> >> > which
> >> >> >> >> > it would go into some
> >> >> >> >> > parameter namespace, but should be a metadata attribute,
> >> >> >> >> > ittm:forcedDisplay
> >> >> >> >>
> >> >> >> >> forcedDisplayModeParameter != itts:forcedDisplay.
> >> >> >> >> forcedDisplayModeParameter would be a parameter passed by the
> >> >> >> >> application to the processor, not a parameter within the
> >> >> >> >> document.
> >> >> >> >
> >> >> >> >
> >> >> >> > What do you mean by "application" in this context? I also don't
> >> >> >> > know
> >> >> >> > what
> >> >> >> > parameter means in this context, e.g., what does it mean
> vis-a-vis
> >> >> >> > a
> >> >> >> > TTML
> >> >> >> > parameter, i.e., an attribute expressing a TTML parameter.
> >> >> >> >
> >> >> >> >>
> >> >> >> >>
> >> >> >> >> > in other words, TTML will remain silent on any presentation
> >> >> >> >> > semantics
> >> >> >> >> > of
> >> >> >> >> > such an attribute;
> >> >> >> >>
> >> >> >> >> How would interoperability be achieved?
> >> >> >> >
> >> >> >> >
> >> >> >> > By defining a standard mechanism for expressing conditional
> >> >> >> > content
> >> >> >> > contingent on external processor state, e.g., selected language,
> >> >> >> > whether
> >> >> >> > display of some content is forced or not, etc.
> >> >> >> >
> >> >> >> > I am opposed to a one-off solution to a special case of the
> >> >> >> > conditional
> >> >> >> > content problem. And the forcedDisplay feature is exactly such a
> >> >> >> > special
> >> >> >> > case.
> >> >> >> >
> >> >> >> >>
> >> >> >> >>
> >> >> >> >> Thanks,
> >> >> >> >>
> >> >> >> >> -- Pierre
> >> >> >> >>
> >> >> >> >> On Fri, Jun 20, 2014 at 8:58 PM, Glenn Adams <glenn@skynav.com
> >
> >> >> >> >> wrote:
> >> >> >> >> >
> >> >> >> >> > On Fri, Jun 20, 2014 at 7:05 PM, Pierre-Anthony Lemieux
> >> >> >> >> > <pal@sandflow.com>
> >> >> >> >> > wrote:
> >> >> >> >> >>
> >> >> >> >> >> Hi all,
> >> >> >> >> >>
> >> >> >> >> >> During our last call, I noted two concerns with the
> >> >> >> >> >> itts:forcedDisplay
> >> >> >> >> >> feature as currently drafted.
> >> >> >> >> >>
> >> >> >> >> >> (a) the semantics of the itts:forcedDisplay feature are not
> >> >> >> >> >> sufficiently specified
> >> >> >> >> >> (b) the representation of itts:forcedDisplay as an attribute
> >> >> >> >> >> is
> >> >> >> >> >> not
> >> >> >> >> >> desirable
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > that should read as a style attribute
> >> >> >> >> >
> >> >> >> >> >>
> >> >> >> >> >>
> >> >> >> >> >> To address (a), below is proposed prose:
> >> >> >> >> >>
> >> >> >> >> >> """
> >> >> >> >> >> The presentation processor SHALL accept an optional boolean
> >> >> >> >> >> parameter
> >> >> >> >> >> called forcedDisplayModeParameter, whose value may be set by
> >> >> >> >> >> the
> >> >> >> >> >> application. If not set, the value of
> >> >> >> >> >> forcedDisplayModeParameter
> >> >> >> >> >> shall
> >> >> >> >> >> be assumed to be equal to "false".
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > no, it should not be a parameter, in which it would go into
> >> >> >> >> > some
> >> >> >> >> > parameter
> >> >> >> >> > namespace, but should be a metadata attribute,
> >> >> >> >> > ittm:forcedDisplay
> >> >> >> >> >
> >> >> >> >> > i'm not sure why you wish to lengthen the name unnecessarily
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> >>
> >> >> >> >> >>
> >> >> >> >> >> If the value of forcedDisplayModeParameter is "true", a
> >> >> >> >> >> content
> >> >> >> >> >> element with a itts:forcedDisplay computed value of "false"
> >> >> >> >> >> shall
> >> >> >> >> >> be
> >> >> >> >> >> assumed to have a tts:visibility computed value equal to
> >> >> >> >> >> "hidden",
> >> >> >> >> >> even if tts:visibility is otherwise set to "true".
> >> >> >> >> >> """
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > now, this is again placing style/presentation semantics on
> this
> >> >> >> >> > metadata
> >> >> >> >> > attribute, which is inapropriate
> >> >> >> >> >
> >> >> >> >> >>
> >> >> >> >> >>
> >> >> >> >> >> The idea is to essentially ignore the itts:forcedDisplay
> >> >> >> >> >> attribute
> >> >> >> >> >> unless otherwise specifically requested by the application.
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > i'm not sure what "requested by the application" means here
> >> >> >> >> >
> >> >> >> >> >>
> >> >> >> >> >> This also
> >> >> >> >> >> clarifies that itts:forcedDisplay has "no effect on content
> >> >> >> >> >> layout
> >> >> >> >> >> or
> >> >> >> >> >> composition, but merely determines whether composed content
> is
> >> >> >> >> >> visible
> >> >> >> >> >> or not."
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > if that is the purpose, then the tts:visibility property
> should
> >> >> >> >> > be
> >> >> >> >> > used
> >> >> >> >> > and
> >> >> >> >> > therefore there is no need for a new forcedDisplay attribute
> >> >> >> >> >
> >> >> >> >> >>
> >> >> >> >> >> As next step, I plan to create examples.
> >> >> >> >> >>
> >> >> >> >> >> Re: (b), I am not comfortable rejecting a solution that
> users
> >> >> >> >> >> have
> >> >> >> >> >> devised and implemented based on actual use cases and in the
> >> >> >> >> >> absence
> >> >> >> >> >> of specific guidance and/or prohibition in TTML 1.0.
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > if those users expect that the TTWG would simply adopt a
> >> >> >> >> > solution
> >> >> >> >> > as
> >> >> >> >> > a
> >> >> >> >> > fait
> >> >> >> >> > accompli, then they are naive; an appropriate process would
> >> >> >> >> > have
> >> >> >> >> > been
> >> >> >> >> > to
> >> >> >> >> > bring use cases and requirements to the TTWG first, not
> bring a
> >> >> >> >> > solution
> >> >> >> >> > as
> >> >> >> >> > a given
> >> >> >> >> >
> >> >> >> >> > at this point, I think the best that can be hoped for IMSC is
> >> >> >> >> > to
> >> >> >> >> > define
> >> >> >> >> > a
> >> >> >> >> > metadata attribute ittm:forcedDisplay which is described as a
> >> >> >> >> > hint
> >> >> >> >> > that
> >> >> >> >> > the
> >> >> >> >> > associated content is intended to be selected as a candidate
> >> >> >> >> > for
> >> >> >> >> > display
> >> >> >> >> > by
> >> >> >> >> > a higher level protocol (outside the scope of formally
> defined
> >> >> >> >> > TTML
> >> >> >> >> > processing); in other words, TTML will remain silent on any
> >> >> >> >> > presentation
> >> >> >> >> > semantics of such an attribute;
> >> >> >> >> >
> >> >> >> >> > on the other hand, we may choose in TTML2 to define a
> >> >> >> >> > conditional
> >> >> >> >> > content
> >> >> >> >> > mechanism similar to the SMIL or SVG switch element, that
> could
> >> >> >> >> > address
> >> >> >> >> > this
> >> >> >> >> > use case
> >> >> >> >> >
> >> >> >> >> >>
> >> >> >> >> >>
> >> >> >> >> >> Best,
> >> >> >> >> >>
> >> >> >> >> >> -- Pierre
> >> >> >> >> >>
> >> >> >> >> >
> >> >> >> >
> >> >> >> >
> >> >> >
> >> >> >
> >> >
> >> >
> >
> >
>