W3C home > Mailing lists > Public > public-tt@w3.org > August 2003

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

From: <Johnb@screen.subtitling.com>
Date: Mon, 11 Aug 2003 10:36:01 +0100
Message-ID: <11E58A66B922D511AFB600A0244A722E9EE570@NTMAIL>
To: shayes@microsoft.com
Cc: public-tt@w3.org
Hi Sean,

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"/>


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
    <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?)
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.
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 |
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....
John Birch 

The views and opinions expressed are the author's own and do not necessarily

reflect the views and opinions of Screen Subtitling Systems Limited. 
Received on Monday, 11 August 2003 05:25:39 UTC

This archive was generated by hypermail 2.3.1 : Thursday, 5 October 2017 18:23:59 UTC