Re: Displaying multiple lines in WebVTT

Two questions:

1  when line number addressing is used, which line is meant if the text needs multiple lines?  

2  the existence of soft-wrapped text doesn't answer the question of whether we need hard-wrapped;  we could
   a) say that line breaks in the VTT are treated as whitespace
   b) (a) plus allow <br>
   c) say that line breaks in the VTT file are 'hard'

which are we settling on?


On Apr 18, 2012, at 10:17 , Silvia Pfeiffer wrote:

> On Wed, Apr 18, 2012 at 10:15 AM, Glenn Maynard <glenn@zewt.org> wrote:
>> On Tue, Apr 17, 2012 at 4:45 PM, Silvia Pfeiffer <silviapfeiffer1@gmail.com>
>> wrote:
>>> 
>>> I've had a bit of a chat with some people on the Chrome team that work
>>> on CSS and the balanced text wrapping mode that we are after indeed is
>>> not easy to implement using CSS. It basically requires a new CSS
>>> algorithm.
>> 
>> 
>> Right, it belongs in CSS.  (I found the earlier discussion:
>> http://lists.whatwg.org/pipermail/whatwg-whatwg.org/2011-December/034026.html
>> "basic algorithm should be ...".)
>> 
>> It shouldn't be difficult--at least, no more difficult than any other
>> wrapping algorithm.
>> 
>>> We're considering this to be a new value for text-wrap - something
>>> like "text-wrap: balance;". It would states something along the lines
>>> of what you outlined - basically that it minimizes white space in the
>>> last line of a multi-line paragraph by re-distributing this white
>>> space over all lines and thus making the individual lines shorter. How
>>> a browser implements this would be up to the browser.
>>> 
>>> What we likely need to do is: write a proposal (in a wiki page or so)
>>> for this new mode, explaining our use case. We should then send it out
>>> to the www-style list for general discussion. If you are keen, do go
>>> ahead with preparing such a proposal.
>> 
>> 
>> I don't know if I'll have the bandwidth to explain this from scratch to yet
>> another audience.  I'll try to get to it eventually if someone else doesn't
>> get to it first...
>> 
>> The suggested algorithm is:
>> 
>> 1: Wrap the text using the ordinary word-wrapping algorithm, and let L be
>> the resulting number of lines.
>> 2: For each possible width W, starting at 1 and ending at the maximum
>> wrapping width, do the following:
>> 2.1. Wrap the text to width W, using the ordinary word-wrapping algorithm.
>> 2.2. If the resulting number of lines is less than or equal to than L,
>> return the wrapped text.  Otherwise, continue to the next possible width.
>> 
>> This simply finds the narrowest width that doesn't require additional lines
>> than ordinary wrapping.  This runs in linear time on the size of the input
>> text.  (Of course, this can be optimized without changing the results, by
>> performing a binary search on W instead of a linear one, but that's an
>> implementation detail.)
>> 
>> This may not produce great results for large paragraphs, but it should work
>> well for caption-size text, where the common case is only a few lines.
>> 
>> (Apparently this has been tried before, but it was attempting to find the
>> *optimal* solution, which turns out to be O(n^2).  I believe this solution
>> is more than adequate for WebVTT's needs, and good enough to be of general
>> use; Ian mentioned headings, which this should work well for too.)
> 
> Sounds good to me!
> 
> I don't have the bandwidth right now to do this, but will put it on my
> list for after the current task.
> 
> Cheers,
> Silvia.
> 

David Singer
Multimedia and Software Standards, Apple Inc.

Received on Wednesday, 18 April 2012 05:37:03 UTC