Some Videos not playing even after fixing libffmpeg.so

[Captain Brillo]

Have the latest version, fresh install of ffmpeg library, no good.

How do I play video like these ones at Quartz : https://qz.com

They just show as a black rectangle on the screen - why, please?

[sleeper10]

I only see one video on that site & it plays fine for me on linux. If you're on linux or mac, carefully follow the instructions here:
https://www.slimjet.com/en/libffmpeg.php