So, there are 2147129 bytes of additional data besides the audio and video streams in Space.mp4
Yep. That's exactly the path I took.
8057685995569da18a15912e754e1510181acb8cad31dfcabb9cab367245be2b = sha256("there's a bunch of data at the end of the file I can't identify. the data is uniform and random, so it's almost certainly encrypted.")
Looking at the split binary a bit deeper we get:
$ ent split
Entropy = 7.999908 bits per byte.
Optimum compression would reduce the size
of this 2147129 byte file by 0 percent.
Chi square distribution for 2147129 samples is 273.12, and randomly
would exceed this value 20.80 percent of the times.
Arithmetic mean value of data bytes is 127.4944 (127.5 = random).
Monte Carlo value for Pi is 3.140655128 (error 0.03 percent).
Serial correlation coefficient is -0.001094 (totally uncorrelated = 0.0).
Maybe file can help us out?
$ file split.bin
split.bin: data
It's encrypted, whatever it is. However it's not the right size to be any block cipher I know of.
split.bin https://mega.co.nz/#!SF9m0I5R!xOlTLH6-f8DujD92CYNTt1lpunXWn3pikcLV1ZPXVk4