**Feature summary**
Converting animated images to videos came up in a number of discussions (e.g. T85838, T85840, T101644) so let's have a dedicated place for discussion.
As a reader of Wikipedia (and other Wikimedia projects) I want to be able to quickly load an article that contains a .GIF animation. These animations can be relatively large. Sometimes making up more than 50% of the page load.
For example, the English Wikipedia article on the [[ https://en.wikipedia.org/wiki/Internal_combustion_engine | Internal combustion engine ]] is 6.23MB when fully loaded in a web browser. 3.78MB of that size (more than half!) is [[ https://commons.wikimedia.org/wiki/File:4StrokeEngine_Ortho_3D_Small.gif | this single embedded GIF ]]. Converting that GIF to a webm file results in an animation of the same quality at 182KB.
Given that webm is supported in many browsers, but not all, there would potentially need to be some fallback to GIF files.
Additionally, this would allow the user to have browser-native media controls to manage playback (such as pausing the animation).
**Use case(s)**
Any wiki page that has an embedded GIF or APNG animation.
**Benefits**
* Readers of Wikimedia projects use less data to read articles that contain gif animations. HTML5 videos tend to be much smaller ([[ http://gfycat.com/ | Gfycat ]] shows original and converted sizes for popular animated gifs, typically there is an 5x-20x size reduction)
* ability to control playback of animation: pause (T85838) / start in a paused state (T85840)
* streaming
* there are a number of low-level optimizations that probably won't happen for images (streaming, hardware acceleration)
The disadvantage is of course the lack of browser support (although still better than APNG - [[ http://caniuse.com/#feat=webm | WebM support ]], [[ http://caniuse.com/#feat=apng | APNG support ]]).
`ffmpeg` can do the conversion.