[whatwg] Alt attribute for <video> and <audio>

[Remco]

On Mon, Aug 10, 2009 at 4:13 AM, Benjamin
Hawkes-Lewis<bhawkeslewis at googlemail.com> wrote:
> On 10/08/2009 02:22, Silvia Pfeiffer wrote:
>>
>> E.g. when you tab onto a<video>  element, the "alt" tag could give a
>> very brief summary as to what the video is about, e.g. "Elephant
>> Dreams video".
>
> Don't the following already do that:
>
> 1. <video title="Elephant Dreams video" ...
>
> 2. <h3 id="elephants">Elephant Dreams video</h3><video
> aria-labelledby="elephants" ...
>
> 3. <video aria-label="Elephant Dreams video" ...
>
> What would "alt" add here?
>
> --
> Benjamin Hawkes-Lewis
>
>

A title is a short description, and could be the movie title in the
case of a video element. An alt is a textual alternative for the
content. It conveys the same meaning as the img, audio, video, iframe,
... element. It doesn't describe the content: it *is* the content.

For an image this usually works well. An image usually doesn't convey
a lot of meaning. It can be replaced by a simple sentence like "A
young dog plays with a red ball on the grass.".

For video, audio, object, iframe, this is a little sparse. Shortening
Elephants Dream's content to "An old man and a young boy walk through
a surrealistic world and have a conversation." doesn't tell you a lot
about the content. But it is very helpful if the content is not
available. It is even more helpful if it isn't as short as the
previous alt-text for Elephants Dream. If it gives more details about
what you see and hear in the video, you get information that for
example a plot description doesn't provide.

But Elephants Dream may not be a good example for a video where an alt
text would be useful. It's simply too complicated to replace with
alternative text. But if you have a short video that explains
something on Wikipedia, it would be tremendously helpful if the alt
text would convey the same meaning. A video of a ball falling to show
what gravity is, could have the alt text: "A ball accelerates as it
moves down. Next to the ball's trajectory, a speedometer increases
with 9.8 m/s per second.".

Remco