How many different Youtube videos are possible?

Download the podcast of my BBC Radio4 show, Domestic Science (Ep1) www.bbc.co.uk/p...
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 KZbin videos.
Original question on twitter:
/ 755799688759037953
Here is our radio show on the BBC radio player. Let me know if it does not work for you.
www.bbc.co.uk/p...
Our Festival of the Spoken Nerd DVD and download:
shop.festivalo...
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/