UHD video sample in 4:4:4 For my project I need to find or short video (1 min) of a UHD video in 4:4:4
I coudn't find any thanks to google.
I am now considering making one from 4 full HD stream in 4:4:4 but I don't know what tools I could use.

And by the way, although I read it's possible to make a full HD 4:4:4 stream from a 4K 4:2:0 I didn't find any sample available.

Any advice?
You can use ffmpeg, a free command-line tool, to generate some synthetic videos in the required size and pixel format:

Mandelbrot fractal

ffmpeg -f lavfi -i "mandelbrot=s=3840x2160:r=24" -c:v libx264 -pix_fmt yuv444p -t 5 mb444.mov


This will generate a 5 second UHD video @ 24 fps. You can experiment with the various parameters detailed here, such as coloring methods or amount of zoom.

There's also filters to generate patterns as per Conway's Game of Life or a custom cellular automaton, although those will be very 'noisy' with default settings.

You can also use a test pattern as a source:

ffmpeg -f lavfi -i "testsrc=s=3840x2160:r=24" -c:v libx264 -pix_fmt yuv444p -t 5 test444.mov