If you're experiencing "Error Code 102630: This video file cannot be played" on Firefox

i've been scratching my head about it for weeks over this and just solved the issue today - it might not work for everyone experiencing this error, but i'm posting it here in case it does/for future reference.

things i tried that didn't work (but might help you):

• updating/restarting firefox
• updating/restarting windows (or your operating system of choice)
• manually updating the video drivers
• deleting the DNS cache
• deleting the browser cache
• running Firefox in troubleshooting mode (no extensions or add-ons) to make sure it wasn't some extension that broke in an update

what actually worked for me:

1. go to about:config (open a new tab and use that in place of the URL)
2. look up "media.mediasource.enabled"
3. if it's set to "false", set it back to "true" by double-clicking it

i had this configuration set to false in order to get videos to buffer completely instead of just loading a couple minutes at a time and then stopping, but unfortunately this does not seem to play well with most streaming sites/servers. pretty sure it worked well before, but an update must have broken it.