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Re: Roll-up captions in WebVTT

From: David Singer <singer@apple.com>
Date: Tue, 29 Nov 2011 18:05:45 +0100
Cc: public-texttracks@w3.org
Message-id: <35168A1A-34D9-4C4D-9E75-7751867DA1D8@apple.com>
To: Christian Vogler <christian.vogler@gallaudet.edu>
At the moment, I can't think of a way of doing even jump-scroll without repeating text, unless (as is very likely) I am being dense.

Maybe someone could correct me if the best practice on jump-scroll is something other than repeat?


On Nov 29, 2011, at 17:40 , Christian Vogler wrote:

> This is not quite true if the text is duplicated in the WebVTT file.
> This would present serious accessibility issues for people who use
> screenreaders (and that includes the deaf-blind population). It also
> would make searching and indexing harder if text were duplicated.
> 
> Christian
> 
> On Tue, Nov 29, 2011 at 11:33 AM, David Singer <singer@apple.com> wrote:
>> I think a fundamental question that needs addressing is whether we expect roll-up to be (a) 'part of' the core VTT vocabulary or (b) a presentational issue that is 'optional'?
>> 
>> I tend to think the latter.  Yes, maybe smooth roll-up is easier on the eye than jump-scroll, but the same information is presented.
>> 
>> If that is the case, I think using CSS transitions is a good candidate.  Alas, we don't use CSS positioning (for obvious reasons -- positioning DOES have to be part of the core of VTT).  But that doesn't hose us.
>> 
>> Consider a stream that has Line1, Line2, . LineN, showing in a three-line area.  A simple way to jump scroll that is simply to repeat each line, every time it 'moves' in the 3-line display.
>> 
>> <blank>
>> <blank>
>> Line1
>> 
>> then
>> 
>> <blank>
>> Line1
>> Line2
>> 
>> Line1
>> Line2
>> Line3
>> 
>> Line2
>> Line3
>> Line4
>> 
>> displayed simply, the lines appear to jump.
>> 
>> If we can convince the CSS engine that Line1 in the first cue is the same as Line1 in the second, we could ask for a transition on, say, 'y'.  That's pretty easy to do with markup -- if a line of text in two consecutive cues has the same marked-id, then it's the same, and any CS transitions declared on its class apply, if you use CSS.
>> 
>> Saying CSS transitions can be used to smooth out display transitions also allows for fade-in/fade-out (transition on color), and so on.
>> 
>> 
>> David Singer
>> Multimedia and Software Standards, Apple Inc.
>> 
>> 
> 
> 
> 
> -- 
> Christian Vogler, PhD
> Director, Technology Access Program
> Department of Communication Studies
> SLCC 1116
> Gallaudet University
> http://tap.gallaudet.edu/
> VP: 202-250-2795

David Singer
Multimedia and Software Standards, Apple Inc.
Received on Tuesday, 29 November 2011 17:06:18 GMT

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