So in all my trial , I have introduce en error in the video path /path/path/FooBar.mp4 as those test where taking place under Windows this time, the front / was making the file unreachable, "funny" in the console no error about that, but about codec that is not found..... O_o
MP4
it worked with
html
...
<source src="path/FooBar.mp4" type="video/mp4">
...
<!-- so without specifying the codec, at least -->
MKV
I've tried everything so far, I didn't managed to make it work :/
so it seem that finally Firefox do not support MKV with AV1
when I open .mp4 container version of it, by file path (url bar) like file:///X:/path/FooBar.mp4 it works, so Firefox can Open it… (now still to make it work inside an html page )
Thank you @IsoKiero@sopuli.xyz !
\ This is the solution.
unfortunately I can't apply it, because the NAS is a closed proprietary 💩