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

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.

Cheers,
Silvia.

Received on Monday, 5 May 2014 11:38:53 UTC