Am I doing something wrong? The downloaded video mp4 seems highly broken. I see two side-by-side copies of the content within the frame, with artifacts that make it impossible to read anything.
It's a 23 minute video that is 21mb. The video quality is (intentionally?) extremely low.
It's definitely a playback issue. VLC is rendering it incorrectly while Firefox is handling the same file just fine (albeit with the expected low quality for the file size).
It’s a vlc issue with h265 - I actually noticed this with videos from defcon last year. Pull the YouTube version or reencode to h264 to fix.