Just to tell you, maybe someone buys this from you  but a bot can SEE what is happening on the screen. And a bot can play the video, watch 2 seconds, save it, then do this for the new video, and compare them.

I myself have created a bot that plays on BSPIN and BitStarz!!!! Fully Automatic! Sees Everything and acts on Every Occasion.

Simpler way to get around your antibot?
https://stackoverflow.com/questions/7124744/how-do-i-detect-which-video-source-is-playing-with-html5-video

Just receive 1 KB of the current playing file, then compare it to the next one.

Maybe you can alter the video and add some effects every time. That would prevent this. But that is ultimately detectable using AI / ML. Cause its "1" video, being altered.
Better use hcaptcha, dont waste your time.

Hcaptcha is basicly doing that, altering the picture every time, but it does not alter it itself, it uses data from other sources. showing you altered pictures of the same thing. Wanting you to find "same" pictures.

Hope you get on the right path. I dont have time to test your code, so do it yourself.
Cheers.