Re: Support for advanced caption features (inc rollup)

Ok so if the use case is "allow software developers based in the US who 
believe they will be covered by the CFR 79.103 rules to support captions 
while only implementing WebVTT", we need to have the following features:

> (1) [...] caption text may be displayed within one or separate caption 
> windows [in a mode where text] appears all at once (pop-on),

This we've done.


> caption text may be displayed within one or separate caption windows [in 
> a mode where text] scrolls up as new text appears (roll-up)

This we don't support, so see below.


> caption text may be displayed within one or separate caption windows [in 
> a mode where] each new letter or word is displayed as it arrives 
> (paint-on).

I presume that by "as it arrives" they don't literally mean that because 
that would be the dumbest thing on the Web (we'd just have to show all the 
captions at once before the user hit play, as soon as we downloaded the 
VTT file). If we instead assume they mean "as the cue text becomes 
relevant", then we support that (it is equivalent to "pop-on"). If we 
instead assume that they mean "as the letter or word is heard on the audio 
track", then we support that too, using hte karaoke features (just hide 
the :future text and put time stamps everywhere).


> (2) Character color. All apparatus shall implement captioning such that 
> characters may be displayed in the 64 colors defined in CEA-708 and such 
> that users are provided with the ability to override the authored color 
> for characters and select from a palette of at least 8 colors including: 
> white, black, red, green, blue, yellow, magenta, and cyan.

This we support via CSS and CSS user style sheets (the latter of which can 
be exposed as UI). It does mean that FCC-compliant WebVTT browser 
implementations will have to support CSS.


> (3) Character opacity. All apparatus shall implement captioning such 
> that users are provided with the ability to vary the opacity of 
> captioned text and select between opaque and semi-transparent opacities.

CSS colours include opacity control.


> (4) Character size. All apparatus shall implement captioning such that 
> users are provided with the ability to vary the size of captioned text 
> and shall provide a range of such sizes from 50% of the default 
> character size to 200% of the default character size.

This we support via CSS user style sheets (which can be exposed as UI).


> (5) Fonts. All apparatus shall implement captioning such that fonts are 
> available to implement the eight fonts required by CEA-708 and § 
> 79.102(k). Users must be provided with the ability to assign the fonts 
> included on their apparatus as the default font for each of the eight 
> styles contained in § 79.102(k).

Assuming implementations ship with suitable fonts, we support this to the 
letter of the text. However, CSS does not support a distinction between 
"monospace serif" and "monospace sans-serif", and "casual" has no good 
generic mapping either, so we don't support this in a useful way (you have 
to explicitly list font names). That's probably ok though.


> (6) Caption background color and opacity. All apparatus shall implement 
> captioning such that the caption background may be displayed in the 64 
> colors defined in CEA-708 and such that users are provided with the 
> ability to override the authored color for the caption background and 
> select from a palette of at least 8 colors including: white, black, red, 
> green, blue, yellow, magenta, and cyan. All apparatus shall implement 
> captioning such that users are provided with the ability to vary the 
> opacity of the caption background and select between opaque, 
> semi-transparent, and transparent background opacities.

Check, as above for the text colour.


> (7) Character edge attributes. All apparatus shall implement captioning 
> such that character edge attributes may be displayed and users are 
> provided the ability to select character edge attributes including: no 
> edge attribute, raised edges, depressed edges, uniform edges, and drop 
> shadowed edges.

This we don't do, and CSS doesn't either. See below.


> (8) Caption window color. All apparatus shall implement captioning such 
> that the caption window color may be displayed in the 64 colors defined 
> in CEA-708 and such that users are provided with the ability to override 
> the authored color for the caption window and select from a palette of 
> at least 8 colors including: white, black, red, green, blue, yellow, 
> magenta, and cyan. All apparatus shall implement captioning such that 
> users are provided with the ability to vary the opacity of the caption 
> window and select between opaque, semi-transparent, and transparent 
> background opacities.

Not sure how this varies from 6, but as far as I can tell, this is handled 
by CSS, so as above.


> (9) Language. All apparatus must implement the ability to select between 
> caption tracks in additional languages when such tracks are present and 
> provide the ability for the user to select simplified or reduced 
> captions when such captions are available and identify such a caption 
> track as “easy reader.”

We don't do the easy reader part. See below.


> (10) Preview and setting retention. All apparatus must provide the 
> ability for the user to preview default and user selection of the 
> caption features required by this section, and must retain such settings 
> as the default caption configuration until changed by the user.

This is supportable by UAs regardless of VTT.


Ok so that leaves three use cases we don't support:

 Allow software developers based in the US who believe they will be
 covered by the CFR 79.103 rules to support captions while only
 implementing WebVTT, by allowing caption text to be displayed within
 one or separate caption windows in a mode where text scrolls up as
 new text appears.

 Allow software developers based in the US who believe they will be
 covered by the CFR 79.103 rules to support captions while only
 implementing WebVTT, by allowing character edge attributes to be
 displayed, including: no edge attribute, raised edges, depressed
 edges, uniform edges, and drop shadowed edges.

 Allow software developers based in the US who believe they will be
 covered by the CFR 79.103 rules to support captions while only
 implementing WebVTT, by providing the ability for the user to select
 simplified or reduced captions when such captions are available and
 identify such a caption track as 'easy reader'.

Question: Why have the people who keep asking for the first on the basis 
that it's legally required not even mentioned the other two?

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'