Given that this question is unanswerable as written, except by someone with access to the original code, can we speculate about how that notebook was able to play an mp4?

it seems to play too well for it to be a ListAnimate on a series of Image objects

@JasonB. challenge accepted, but tell me how to import mp4 frames first :)

@Kuba I imagine it has to use an external library that you can Read frames from. A raw import of all the data seems like it would just be too slow.

@b3m2a1 you can pre-read them, but my point was that I can't even import mp4 movie as frames.

@Kuba I see. I had thought there was an MP4 importer but I guess I only saw AVI.

@b3m2a1 there is but it assumes audio file

@Kuba - I would start here github.com/kmisiunas/ffmpeg-mathematica

I never tried to use that package before, but my workflow for making movies with mathematica has always been to export frames as png files and combining them with ffmpeg, maybe that would allow to do it all natively

er, "natively"

@Kuba @b3m2a1 Are you aware of MathMF ? It imports the frames from MP4 fine. Windows 64 only. The frames are not compressed, so you rapidly get huge memory use. (Maybe I miss something from your context)

?! It would be strange that you don't know MathMF, taking account of your background of SE.