ffmpeg ProRes proxy encodings comparison

comparison.md

Results

V-Codec	A-Codec	profile	pix_fmt	qscale	File Size	Speed
prores_ks	pcm_s16le				1610 MB	164 %
prores_ks	pcm_s16le	proxy			353 MB	103 %
prores_ks	pcm_s16le	proxy		4	740 MB	726 %
prores_ks	pcm_s16le	proxy		10	424 MB	738 %
prores_ks	pcm_s16le	proxy		12	375 MB	762 %
prores_ks	pcm_s16le	proxy		16	309 MB	729 %
prores_ks	pcm_s16le	proxy		20	266 MB	735 %
prores_ks	pcm_s16le	proxy		24	236 MB	766 %
prores_ks	pcm_s16le	proxy	yuv422p10le	16	309 MB	749 %
prores_ks	pcm_s16le	proxy	yuv420p	16	309 MB	772 %
prores_ks	pcm_s16le	proxy	yuv422p	16	309 MB	767 %
prores_ks	pcm_s16le	proxy	yuv444p	16	360 MB	591 %
prores_ks	pcm_s24le	proxy		16	314 MB	759 %
prores_ks	copy	proxy		16	300 MB	767 %
prores_ks	pcm_s16le	lt			772 MB	120 %
prores_ks	pcm_s16le	lt		16	391 MB	758 %
prores_ks	pcm_s16le	hq			1610 MB	160 %
prores_ks	pcm_s16le	hq		16	604 MB	733 %

Input file

Used on an 12 hours long video input. Both C: and E: are fast SSDs.

Duration: 12:16:15.22, start: 0.000000, bitrate: 5173 kb/s
Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, smpte170m), 1280x720 [SAR 1:1 DAR 16:9], 5003 kb/s, 60 fps, 60 tbr, 90k tbn, 120 tbc (default)
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 153 kb/s (default)

Base command

ffmpeg -i ~/Desktop/video.mp4 -c:v prores_ks -c:a pcm_s16le -t 00:01:00 -y /e/Premiere/Proxies/video.mov

pxfmt is automatically set to yuv422p10le if I don't specify it.

I have the following error: Incompatible pixel format 'yuv420p' for codec 'prores_ks', auto-selecting format 'yuv422p10le'
how do you make the test with yuv420p?