Gamma confusion

[meidoqt]

Anyone knowledgeable about this stuff please explain how this makes sense.

My confusion comes from not understanding why mpv would report any other value than what I explicitly set as --target-trc=, bt.1886 in this case.

Windows 11, mpv v0.41.0-162-g9ccd8899f

SDR file

mpv --no-config sdr.mkv Reported display transfer: bt.1886
mpv --no-config --target-trc=bt.1886 sdr.mkv Reported display transfer: gamma2.2
mpv --no-config --treat-srgb-as-power22=no --target-trc=bt.1886 sdr.mkv Reported display transfer: srgb
mpv --no-config --target-colorspace-hint=no --target-trc=bt.1886 sdr.mkv Reported display transfer: bt.1886
mpv --no-config --target-colorspace-hint-strict=no --target-trc=bt.1886 sdr.mkv Reported display transfer: bt.1886

HDR file

mpv --no-config dovi.mkv Reported display transfer: gamma2.2
mpv --no-config --target-trc=bt.1886 dovi.mkv Reported display transfer: gamma2.2
mpv --no-config --treat-srgb-as-power22=no --target-trc=bt.1886 dovi.mkv Reported display transfer: srgb
mpv --no-config --target-colorspace-hint=no --target-trc=bt.1886 dovi.mkv Reported display transfer: bt.1886
mpv --no-config --target-colorspace-hint-strict=no --target-trc=bt.1886 dovi.mkv Reported display transfer: bt.1886

[Jules-A]

To add to the confusing (although it's likely a bug):
mpv --no-config --vo=gpu-next --sdr-adjust-gamma=yes --treat-srgb-as-power22=auto --target-trc=gamma2.4 "non-hdr.mp4"
mpv --no-config --vo=gpu-next --target-trc=gamma2.4 "non-hdr.mp4"
mpv --no-config --vo=gpu-next --sdr-adjust-gamma=yes --target-trc=gamma2.4 "non-hdr.mp4"
just gives me gamma2.2 (or pretty much any other combination), I can't actually find a way to set it to gamma2.4 even with my monitor set to gamma 2.4...

[kasper93]

--target-colorspace-hint-strict=no

[Jules-A]

That's so confusing and if it isn't going to be changed, definitely needs better documentation.

[kasper93]

The output format selection depends of few options that interact with each other.

SDR file:

mpv --no-config sdr.mkv Reported display transfer: bt.1886

No gamma adjustment is made, bt.1886 is passed through with minimal changes. This is not matching swapchain configuration, see --sdr-adjust-gamma

mpv --no-config --target-trc=bt.1886 sdr.mkv Reported display transfer: gamma2.2

You explicitly asked for target-trc=bt.1886, but your compositor doesn't support it and we fallback to sRGB/gamma2.2 output. See --target-colorspace-hint-strict=no for override.

mpv --no-config --treat-srgb-as-power22=no --target-trc=bt.1886 sdr.mkv Reported display transfer: srgb

Same as the above, fallback to sRGB, but with treat-srgb-as-power22=no

mpv --no-config --target-colorspace-hint=no --target-trc=bt.1886 sdr.mkv Reported display transfer: bt.1886

When there is no hint, we don't care about swapchain configuration and always use target-trc value.

mpv --no-config --target-colorspace-hint-strict=no --target-trc=bt.1886 sdr.mkv Reported display transfer: bt.1886

This is the same as first case, no gamma adjustment. This should have --sdr-adjust-gamma to respect target-trc too.

HDR file:

It should be clear by now why it does that it does. Let me know if you have specific questions about this.