Colin Barrett wrote:
> On May 28, 2007, at 1:49 AM, Benjamin Hawkes-Lewis
wrote:
[snip]
>> If a screen reader read (for example):
>>
>> quote Dorothy encounters the Lion end quote
>>
>> That would be rather strange, wouldn't it?
>
> I dunno, I think that might be helpful. It's semantic
information that
> it's a portion of a larger document.
This is a tempting argument, but in theory and practice a
problematic
one. <q> and <blockquote> are not merely
intended to be "portions of a
larger document" but to be /quotations/:
http://www.w3.org/TR/html401/struct/text.html#h-9.2.2
I'm not sure that a thumbnail really is a quotation,
although it's
clearly conceptually close to one. When people talk of
quotations from
movies in everyday speech, they are talking about quotations
from the
dialogue not stills, e.g.:
http://www
.imdb.com/title/tt0032138/quotes
I don't think "quote Dorothy encounters the Lion end
quote" would be a
human readable hint that it's a thumbnail from a video.
Unless you
happen to be a microformats guru. ;)
> Using a span tag as you suggest provides the UA with
zero semantic information.
I'd prefer to provide zero information than potentially
misleading
information. I suppose one could prefix the alt with
"still:" though:
alt="still: Dorothy encounters the Lion"
So then you might hear:
graphic still Dorothy encounters the Lion link The Wizard of
Oz
A microformat parser could remove everything up to and
including the
first colon to get to the alternative text proper.
> I suspect having alt
> tags that just link to a video which perhaps they don't
want to watch is
> annoying to people with screen readers -- although I
think I would need
> a bit more data about how screen readers work and how
they're used to
> really say anything else.
I believe your suspicion is wrong for three reasons:
1. Most screen reader users are not deaf as well as blind,
and many
screen readers still have some sight. So most screen reader
users are as
likely to enjoy watching videos online as you and I. Their
big problem
with sites like YouTube is that it's too hard to /find/
videos, not to
watch them:
http://www.bbc.co.uk/blogs/acces
s20/2007/05/access_20_interview_mark_prous.shtml
2. Most video formats, include Flash video and Quicktime,
can include
captioning which mainstream screen readers can push to a
braille display
for deafblind users. Videos /should/ include captioning and
authors
should make it clear when they do not: and ideally provide a
transcript
as an alternative. There are now captioning websites that
either make it
easy to add captions to online video or will even caption it
for you for
free on request:
http://www.bbc.co.uk/blogs/access2
0/2007/05/captioning_video_gets_easier.shtml
3. Even if a video is completely inaccessible for some
reason, screen
reader users may use the alternative text to understand why
the author
is referring to that video, to share the video or thumbnail
with sighted
friends or colleagues, or to demand an accessible
alternative. Just
hiding inaccessible materials would produce confusion.
On an even more basic technical level: leaving out alt would
result in
some screen readers reading the image src attribute. Leaving
alt blank
would result in some screen readers reading the href for any
surrounding
anchor link when alt provides the only text content for the
link, e.g.:
<a href="http://
www.example.com/video"><img
alt=""></a>
By default, Window-Eyes would read something like:
link h t t p colon slash slash w w w dot example dot com
slash video
Commonly, I think, the user will have reduced the verbosity
to strip out
most punctuation and only have to suffer:
link h t t p w w w example com video
Takeaway: include an alt for all images; and always include
an alt with
actual text if the img is the /sole/ content of the link.
--
Benjamin Hawkes-Lewis
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