Video support

[petsuter]

In Sphinx images can be included with .. image:: or .. figure::.
But there is no support for videos yet, right?

It would be nice to have a .. video:: or even support videos in .. figure::.

A workaround is to use:

.. raw:: html

   <video controls src="video.mp4"></video>

This works quite well! ✨

But:

• The workaround has none of the .. figure:: features, like a legend etc.
• The workaround is too complicated for non-HTML-experts.
• The workaround is too complicated if repeated for many videos.
• The workaround will never work for non-HTML output formats.
• Sphinx does not know to copy the video file.
• ...

In the past video support was probably completely out-of-scope, but maybe nowadays it is easy and appropriate to support it?

Thanks for your consideration.

[tk0miya]

+1: Nowadays, video is an important medium. It's reasonable to support.
-0: The only HTML supports it. Other formats do not.
-0: It would be better to add it to the original docutils spec. So it should be proposed into docutils project.

[astrojuanlu]

@gmilde notes in sphinx-dev:

I suppose the issue "Video support #7404" may be closed with a link to
https://docutils.sourceforge.io/HISTORY.html#release-0-17-2021-04-03

docutils/writers/html5_polyglot/init.py

[...]

Use

(Unless Sphinx patches the image/figure directive handling in a way that
breaks Docutils support for moving images.)