Fixing background video not playing on certain small factor devices (android)

[vanch3d]

There has been reports in the past of background video not playing properly on some devices. See #1027 or #2179.

I've been facing the same issue recently when trying to play Reveal.js presentations on some IoT-type devices (android board, with WebView) and even from my phone (Samsung, Android 11, both Samsung Internet and Brave)

Could not easily reproduce the problem because of also using embedded videos (full screen) that where properly working.

Until I spotted a slight difference between the two video injection: the background video didn't have type added to the source tag generated from the data-background-video attribute in Reveal.js

The solution in this PR seems to be fixing the problem on all my devices. I cannot explain why it is working (or bugging in the first place), nor whether it will now work on every devices, including older versions of OS or browsers.

Also, worth noting that the solution in this PR is simply generating the MIME type out of the file extension, which is not a very reliable solution. But it will do, unless we want to make the specification of the data-background-video attribute more complicated

[vanch3d]

An alternative suggestion for a fix would be to have the MIME type included in the data-background-video using a secondary string delimiter, for example :

 <section
        data-background-video="http://example.com/video1.mp4:video/mp4,http://example.com/video2.webm:video/webm"
        data-background-video-loop
        data-background-video-muted
      >
        <h2>Background Video</h2>
</section>

This will still be backward compatible with the current handling of multiple sources and make the specification and validity of the MIME the responsibility of the designer, not the JS package.

[hakimel]

Solving this for most cases without requiring additional authoring seems like a good solution for now. We can always add the ability to provide explicit types via new syntax later.

I update the implementation a little so that we only set known/valid MIME types instead of always using the file extension. c5d5498

[hakimel]

Thanks for fixing this!