How many different Youtube videos are possible?

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In this video I start with how many 256×256 greyscale images are possible and work my way up to the maximum number of possible TH-cam videos.
Original question on twitter:
/ 755799688759037953
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Galaxy M81 image credit: NASA/JPL-Caltech/ESA/Harvard-Smithsonian CfA
Music by Howard Carter
Design by Simon Wright
MATT PARKER: Stand-up Mathematician
Website: standupmaths.com/
Maths book: makeanddo4D.com/
Nerdy maths toys: mathsgear.co.uk/