Currently, embedded videos show a thumbnail with a play button and require manual activation to play. Meanwhile, GIF animations have been in autoplay mode since we allowed GIFs in 2003 or so.
This encourages moving diagrams and even video captures representing a short movement sequence to be done as GIFs, which have various limitations (256-color palette, primitive compression, no playback controls, difficulty supporting multiple resolutions efficiently, etc).
It would be nice to provide the positive aspects of animated GIF behavior optionally when using 'proper' video formats:
* autoplay with sound muted
* looping
plus the abilities of video:
* full color
* better compression for real video
* ability to unmute if sound is available
* ability to pause/seek
* scaling/transcoding infrastructure already handles long-running processes on large input files well
The keyword could look like this:
```
[[File:Fooey.webm|autoplay]]
```
or in a bigger context:
```
[[File:orbit2.webm|autoplay|thumb|300px|Two bodies of different [[mass]] orbiting a common [[Barycentric coordinates (astronomy)|barycenter]]. The relative sizes and type of orbit are similar to the [[Pluto]]–[[Charon (moon)|Charon]] system.]]
```
vs this existing gif usage on https://en.wikipedia.org/wiki/Orbit ...
```
[[File:orbit2.gif|thumb|300px|Two bodies of different [[mass]] orbiting a common [[Barycentric coordinates (astronomy)|barycenter]]. The relative sizes and type of orbit are similar to the [[Pluto]]–[[Charon (moon)|Charon]] system.]]
```
Open questions:
* do we need just 'autoplay', or 'loop', or both?
* how to express the silent-ness on no-JS output?
* start/stop times necessary? (double-check the existing support here)
* do we need to add a mute state indicator, like you see on Twitter or Facebook autoplay videos?
* any autoplay limitations/surprises? (eg, pretty sure autoplay is disabled on iOS)
* should this actually be the default behavior? or something more limited?