dithering introduces distracting pattern/dots in shadows/dark areas

mpv Information

mpv 0.38.0 Copyright © 2000-2024 mpv/MPlayer/mplayer2 projects
 built on Apr 20 2024 00:22:40
libplacebo version: v7.349.0 (v6.338.0-124-gd0eb997-dirty)
FFmpeg version: N-114897-gbba996d6c
FFmpeg library versions:
   libavutil       59.15.100
   libavcodec      61.5.103
   libavformat     61.3.100
   libswscale      8.2.100
   libavfilter     10.2.101
   libswresample   5.2.100

Other Information

• Windows version: Windows 10 22H2 Build 19045.4170)
• GPU model, driver and version: intel HD Graphics 4600, driver: 20.19.15.5171
• Source of mpv: https://sourceforge.net/projects/mpv-player-windows/files/
• Introduced in version: present since v36.0

Reproduction Steps

watch 4k 10bit source on 8bit sdr monitor/tv with dither-depth=8 dither=fruit
and watch at dark areas/shadows

Expected Behavior

a dithering solution that doesn't deteriorate the image with this weird pattern/dots in shadow/dark areas

Actual Behavior

dithering introduces this weird pattern/dots in shadow/dark areas which in itself prevents from ever having any real black on screen.

Log File

mpv --gpu-debug
output.txt
mpv --log-file
output x.txt

Sample Files

Screenshots, boosted luminance for demonstration purpose.

pattern zoomed in

dither off

dither on

I carefully read all instruction and confirm that I did the following:

• I tested with the latest mpv version to validate that the issue is not already fixed.
• I provided all required information including system and mpv version.
• I produced the log file with the exact same set of files, parameters, and conditions used in "Reproduction Steps", with the addition of --log-file=output.txt.
• I produced the log file while the behaviors described in "Actual Behavior" were actively observed.
• I attached the full, untruncated log file.
• I attached the backtrace in the case of a crash.

Start by reproducing the issue with a 4K 10-bit source on an 8-bit SDR display using dither-depth=8 and dither=fruit, comparing dither on and off. Review the attached debug and log files alongside the dithering path; done means dark areas no longer show the distracting pattern while preserving the intended conversion behavior.