"Warren Turkal" <>
wrote on 07/18/2008 04:29:01 PM:
>
> Does the MPEG4 spec have a similar restriction? It seems to me that
> allowing quick changes in a video could also cause an epileptic fit.
>
I don't know. Unfortunately even JTC1/SC34 members
are not given free access to other ISO standards. So short of shelling
out $70 to buy a copy, I cannot check. Ironically, if we did want
to make a statement on the safety implications of flickering, we are required
to do so according to ISO/IEC Guide 51 "Safety aspects -- Guidelines
for their inclusion in standards", but that is not available to us
free. That would cost $63.
But one assumes that there is a risk with MPEG4
as well. At the very least you could have a video of an ODF editor
doing a table refresh really fast.
In any case, there is some good background here on
the general problem:
http://en.wikipedia.org/wiki/Blink_element
http://en.wikipedia.org/wiki/Photosensitive_epilepsy
Sounds like the risky range is 2 Hz - 55 Hz, which
should be avoided according to Section 508 of the Rehabilitation Act:
http://www.section508.gov/index.cfm?FuseAction=Content&ID=12#Web
What I'm not sure is whether "flicker" is
the same as update, or is "flicker" just a symptom of poor graphics
layer, e.g., cannot update text without first blanking it out. With
double-buffering, XOR'ing images, etc., we should have be able to have
flicker-free updates if we wanted. Your mouse doesn't flicker when
you move it around your screen, does it? That is more than 2Hz.
-Rob
