vo_gpu_next: `background-color` is affected by gamma adjustments

[atrxia1]

mpv Information

mpv v0.40.0-443-gbbafb7488 Copyright © 2000-2025 mpv/MPlayer/mplayer2 projects
 built on Nov  7 2025 02:13:28
libplacebo version: v7.357.0 (v7.351.0-89-g06992a5-dirty)
FFmpeg version: N-121682-g7435a3180
FFmpeg library versions:
   libavcodec      62.19.100
   libavdevice     62.2.100
   libavfilter     11.9.100
   libavformat     62.6.101
   libavutil       60.17.100
   libswresample   6.2.100
   libswscale      9.3.100

Other Information

- Windows version: 10.0.26200.6901
- GPU model, driver and version: AMD latest
- Source of mpv: zhongfly
- Latest known working version: None
- Issue started after the following happened: -

Reproduction Steps

--background=color --background-color=<any near-black or grey color>

Use in combination with either one of the following:

--treat-srgb-as-power22=auto

or

--target-colorspace-hint-strict=no --target-trc=gamma2.2

Expected Behavior

Inputted RGB values for --background-color are not converted to G22 values.

Actual Behavior

Inputted values do not match the outputted values due to gamma conversion.

There could be a new renderer toggle called --blend-background=<yes|no> (default: no) that allows users to choose whether or not they want the background to be affected by color adjustment.

Log File

output.txt

Sample Files

No response

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

• [x] I tested with the latest mpv version to validate that the issue is not already fixed.
• [x] I provided all required information including system and mpv version.
• [x] 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.
• [x] I produced the log file while the behaviors described in "Actual Behavior" were actively observed.
• [x] I attached the full, untruncated log file.
• [x] I attached the backtrace in the case of a crash.

[atrxia1]

Follow-up from: https://github.com/mpv-player/mpv/pull/17009#issuecomment-3496586575

[llyyr]

Fixed by https://code.videolan.org/videolan/libplacebo/-/merge_requests/762

[atrxia1]

That seems to only affect target-contrast, not target-trc or other options that modify target gamma values. Also, this issue isn't affected by black backgrounds anyways, since complete black is mapped to the same color values in RGB and RGB->G22.