[whatwg] accessibility management for timed media elements, proposal
singer at apple.com
Sat Jun 9 14:26:09 PDT 2007
At 16:35 +0100 9/06/07, Benjamin Hawkes-Lewis wrote:
>Dave Singer wrote:
>>we promised to get back to the whatwg with a proposal for a way to
>>handle accessibility for timed media, and here it is. sorry it
>>took a while...
>Three cheers for Apple for trying to tackle some of the
>accessibility issues around video content! :)
Many thanks for all your helpful comments!
>Without trying to assess whether CSS media queries are the best
>approach generally, here's three particular issues I wanted to raise:
>1. Property values
>I honestly don't think the property values are well-named. "either"
>is confusing and vague; "dont-want" is a misspelled colloquialism.
We struggled with this also; suggestions are welcome.
>How about one of the following possibilities:
>(This seems more natural to me than the original proposal.)
>(Has the consistency of using the same word as the basis for each
>value. OTOH "prefer-not" and "no-preference" may be confusing if
>your English isn't that good.)
>("desire" has the minor advantages of being in Ogden's basic English
>word list and being common to Romance languages thanks to a Latin
>root. OTOH it's slightly longer.)
nice (in my personal opinion).
>2. Conflict resolution
>The proposal does not describe how conflicts such as the following
>would be resolved:
><video ... >
> <source media="all and (captions: want;high-contrast-video:
>dont-want)" ... />
> <source media="all and (captions: dont-want;high-contrast-video:
>want)" ... />
There is no suitable source here; it's best to have something (late)
in the list which is less restrictive.
>Because style rules cascade, this sort of conflict doesn't matter
>when media queries are applied to styles. But you can only view one
>3. (Even more) special requirements
>The suggested list of media features is (self-confessedly) not
>exhaustive. Here's some things that seem to be missing:
>a) I should think sign-language interpretation needs to be in there.
>sign-interpretation: want | dont-want | either (default: want)
>Unless we want to treat sign interpretation as a special form of
>subtitling. How is subtitling in various languages to be handled?
I think we assume that a language attribute can also be specified, as today.
I have to confess I saw the BBC story about sign-language soon after
sending this round internally. But I need to do some study on the
naming of sign languages and whether they have ISO codes. Is it true
that if I say that the human language is ISO 639-2 code XXX, and that
it's signed, there is only one choice for what the sign language is
(I don't think so -- isn't american sign language different from
british)? Alternatively, are there ISO or IETF codes for sign
>b) Would full descriptive transcriptions (e.g. for the deafblind)
>fit into this media feature-based scheme or not?
>transcription: want | dont-want | either (default: either)
how are these presented to a deafblind user?
>c) How about screening out visual content dangerous to those with
>photosensitive epilepsy, an problem that has just made headlines in
>max-flashes-per-second: <integer> | any (default: 3)
>Where the UA must not show visual content if the user is selecting
>for a lower number of flashes per second. By default UAs should be
>configured not to display content which breaches safety levels; the
>default value should be 3 /not/ any.
I think we'd prefer not to get into quantitative measures here, but a
boolean "this program is unsuitable for those prone to epilepsy
induced by flashing lights" might make sense. epilepsy: dont-want -:)
>d) Facilitating people with cognitive disabilities within a media
>query framework is trickier. Some might prefer content which has
>been stripped down to simple essentials. Some might prefer content
>which has extra explanations. Some might benefit from a media query
>based on reading level. Compare the discussion of assessing
>readability levels at:
>reading-level: <integer> | basic | average | complex | any (default: any)
>Where the integer would be how many years of schooling it would take
>an average person to understand the content: basic could be (say) 9,
>average could be 12, and complex could be 17 (post-graduate).
>This wouldn't be easily testable, but it might be useful nevertheless.
Yes, this isn't testable, and is quantitative.
>Postscript: This isn't an accessibility issue but /if/ media queries
>are adopted as a mechanism for serving up the best content for a
>person's abilities, I wonder if they could also be used to enhance
>parental control systems using queries based on PICS:
>So for example, one <source> might have a music video featuring
>uncensored swearing, and another <source> might have the same video
>with the swearing beeped out.
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