WEBM video looks correct in browsers, but not in video players

Question

Ive been trying to figure out why a webm video renders incorrectly on my desktop...

The correct file can be seen here, however, downloading the file, and trying to play it in VLC/MPC-HC produces a bad video as seen here
(File is tested bad in VLC and MPC-HC, but renders perfectly in chrome and FF)

I've been able to extract the alpha channel with ffmpeg and it looks correct

Is this a poor implementation from the video players? (Other webm files play fine)
Is there a command i can throw into ffmpeg (or similar) to get the webm to look ok?

Answer 1

What the regular video players are showing is just the luma+color planes. You need a premultiplied result for the output you want. Which is what the browsers are doing, in effect. See https://stackoverflow.com/a/43017337/5726027

ffmpeg -c:v libvpx -i base.webm -vf premultiply=inplace=1 out.mp4