user14019: 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?

user1871: 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


14019: <p>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.</p>

<p>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.</p>

<p>Any advice?</p>
 1871: <p>You can use <a href="https://ffmpeg.org/download.html" rel="nofollow">ffmpeg</a>, a free command-line tool, to generate some synthetic videos in the required size and pixel format:</p>

<h3>Mandelbrot fractal</h3>

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

<p>This will generate a <code>5</code> second UHD video @ 24 fps. You can experiment with the various parameters detailed <a href="https://ffmpeg.org/ffmpeg-all.html#mandelbrot" rel="nofollow">here</a>, such as coloring methods or amount of zoom.</p>

<p>There's also filters to generate patterns as per Conway's Game of <a href="https://ffmpeg.org/ffmpeg-all.html#life" rel="nofollow">Life</a> or a custom <a href="https://ffmpeg.org/ffmpeg-all.html#cellauto" rel="nofollow">cellular automaton</a>, although those will be very 'noisy' with default settings.</p>

<p>You can also use a <a href="https://ffmpeg.org/ffmpeg-all.html#allrgb_002c-allyuv_002c-color_002c-haldclutsrc_002c-nullsrc_002c-rgbtestsrc_002c-smptebars_002c-smptehdbars_002c-testsrc" rel="nofollow">test pattern</a> as a source:</p>

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