Re: Roll-up captions in WebVTT

On Dec 5, 2011, at 15:26 , Ian Hickson wrote:

> On Tue, 29 Nov 2011, David Singer 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'?
> 
> When the captions are provided line-by-line, whether live-captioned or 
> not, I can see an argument being made that they should be displayable as 
> roll-up captions.
> 
> However, for live-captioned content that was written with roll-up 
> presentation in mind, I don't really see how you can display it as pop-up 
> in real time (in a rebroadcast where you have all the captions ahead of 
> time, sure, just collapse all the cues into the start of each cue).
> 
> In conclusion, I think it has to be at least (a), though it would be cool 
> to allow (b), though I don't really see how to do it.

In my mind, marks inside the VTT file that somehow say "scroll up smoothly to make way for new lines of text" are 'part of' VTT, whereas, for example,  a technique where it's clear that a line of text was jump-moving from one place to another (up a line) would be amenable to CSS transitions, i.e. would be an optional 'presentational' aspect.

I am not sure CSS transitions lend themselves well to continuous scrolling; one would have to have no ease-in or ease-out, and exact timing, however.

I have to say I am a bit puzzled; given a display of 

This is a line of text
and this is the second

which transitions abruptly to

and this is the second
and the third line follows here

The second line 'jump' scrolls up.  I would have thought legibility would be better if it smooth scrolled up, as it's then visually clear it's the same line, just moved.  But people seem to be saying legibility is worse.  is that an artifact of 608 etc., or a true reflection on the aesthetics of smooth scrolling?


David Singer
Multimedia and Software Standards, Apple Inc.

Received on Saturday, 17 December 2011 00:09:40 UTC