Re: Absolute region positioning (was Re: Alternative approach to scrolling, with demos)

On Mon, May 5, 2014 at 1:38 PM, Silvia Pfeiffer
<silviapfeiffer1@gmail.com> wrote:
> On Mon, May 5, 2014 at 9:17 PM, Philip Jägenstedt <philipj@opera.com> wrote:
>> On Tue, Apr 8, 2014 at 9:21 AM, Silvia Pfeiffer
>> <silviapfeiffer1@gmail.com> wrote:
>>> On Sun, Mar 30, 2014 at 4:41 PM, Philip Jägenstedt <philipj@opera.com> wrote:
>>>>
>>>> == Absolute positioning and scrolling ==
>>>>
>>>> Demo: http://people.opera.com/philipj/2014/03/vttscroll/absolute.html
>>>>
>>>> Finally, an idea for how scrolling might work with absolutely
>>>> positioned cues. You simply position all the cues at the point where
>>>> scrolling should begin, and they'll scroll up from there.
>>>
>>> I've attached a vtt file for you with two "regions". The cues should
>>> each get limited to their "region".
>>>
>>> You can see for yourself how this breaks down with 2 regions present.
>>>
>>> I think it's quite clear that the concept of cue groups codified in
>>> regions is a more appropriate approach than building ad-hoc groups of
>>> captions by trying to group them based on them overlapping each other.
>>
>> For simplicity in the demo, I scrolled all the cues by the same amount
>> without checking if they actually overlap, which of course falls apart
>> when you have two groups of cues. If implemented properly, I don't see
>> that cues scrolling in different parts of the video would be a
>> problem. If scrolling implemented as overlap avoidance, the situation
>> has to be handled anyway.
>>
>> How are overlapping regions handled? Not at all AFAICT, some text
>> would simply be obscured.
>
> Indeed, we're not currently handling overlapping regions. I don't
> think we need to either, because not even CEA708 has an overlap
> avoidance algorithm. Instead, it specifies z-index (called "priority")
> so the author can determine which cue sits in front if overlap
> happens.
>
> I don't mind that actually, because it provides an alternative to the
> default cues which do overlap avoidance.

I do mind. Why should we accept this deficiency just because CEA708
has it? Unless the video is entirely filled with text (unlikely) there
will be a way to show all of it without overlap, so why not deal with
the situation since WebVTT already has overlap avoidance?

Philip

Received on Monday, 5 May 2014 12:16:54 UTC