- From: Christopher Giffard <christopher.giffard@cgiffard.com>
- Date: Wed, 30 Nov 2011 06:48:25 +1100
- To: David Singer <singer@apple.com>
Correct me if I'm wrong, but could the :future / :past pseudo-classes enable this kind of styling? It's possible that we'd need a :current pseudo-class in order to select the last two lines which went past, but maybe this would work too: ::cue:past:last-child, ::cue:past:nth-last-child(2) { … } If we were moving the implementation of roll-up captions to authors though, we need to evaluate this, as the allowed properties don't currently enable enough flexibility to implement roll-up without jumping: http://dev.w3.org/html5/webvtt/#the-'::cue'-pseudo-element Kind Regards, Christopher Giffard (Sorry about the double message David - missed the mailing list with the last one!) On 30/11/2011, at 4:05 AM, David Singer wrote: > 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 Thursday, 1 December 2011 09:21:45 UTC