RE: TT and subtitling/captioning - separating timing from style f rom content

Hi Sean,
 
<SH>

At the BBC f2f we considered adding a 'word' level selector to XPath, so the
example might become:

    <cue select="p1/word(1)" use="a2" dur="1"/>

 

<JB>
I'd forgotten this was talked about at BBC F2F, I suspect that Glenn's
suggestion of adopting XPath range notation is more appropriate - if solely
from a reuse principle :-). However the word selector does have merits (its
more obvious what is happening, and it's more concise). Is the following
correct?
 
    <cue select="#xpointer(p1/range(1.0, 1.1)" use="a2" dur="1"/>

 

BTW I don't see a great issue with what a word selector would select -
probably only Thai and similar languages where you would need to define what
the behaviour was.... (line, character or use-dictionary?)
 
<SH>
On another topic in this thread, the notion of fitting a too long caption in
a fixed size box, one approach might be some temporal additions to the CSS2
overflow property.
 
<JB>
Indeed, I suggested some candidates (see below) :-) Tho' I'm not sure that
they should / could bolt in to CSS.
 
Bear in mind that these candidates come from my experience with
subtitling/captioning - and pre-suppose that there is a desire for a
temporal-flow concept within TT-AF. It may be that TT-AF only supports an
explicit timing mechanism. I would argue that if TT-AF is considered to be
valid content within a SMIL 'container' document - where SMIL may define the
region for the content.... that some from of temporal flow may be desirable.
It's synonymous with video in that sense - in that a video clip is actually
a series of still images flowed over time. SMIL does have some say over what
happens if the content doesn't fit the duration - it would be nice if TT-AF
was intrinsically able to define its own 'frame-rate'.
 
fill-direction - regardless of writing mode - in subtitling/captioning -
regions are filled from different directions depending on where they are on
the screen. E.g a top of screen subtitle will use the uppermost line first -
then the second etc... Conversely a bottom of screen subtitle will use the
lowest line first  - then the bottom two lines etc. This is to minimise the
intrusion of the subtitle into the central picture area. The UA would need a
'hint' in order to decide which direction is appropriate.

fill-mode - basically the size of content used when filling a region - e.g.
all | line | word | fragment.
region-full-clear - is the region cleared when it fills - or does content
shift to make space - and by what extent (none | all | line | word |
fragment)
add-interval - A desired (target) interval between additions (auto | value)
read-interval - The desired (target read-interval) - how long the last
content must 'hang' to allow reading.
tidemark - A subtle wrinkle - you may wish to nominally have just two line
subtitles - but allow three liners if the amount of content demands it. The
tidemark would define when to typically consider a clear down in pop mode -
but might be overwritten by the content / time demands.

 
Of course these concepts are not just limited to TT-AF for subtitling /
captioning - but have application in many other areas....
regards 
John Birch 

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reflect the views and opinions of Screen Subtitling Systems Limited.