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HDR signal peak luminance metadata not sent to the display #10129

@dechamps

Description

@dechamps
  • mpv version: 0.34.0
  • Source of the mpv binary: shinchiro Windows build
  • Windows Version: 11 21H2 22000.613 with HDR mode enabled
  • GPU: NVidia 3080 Ti driver 512.15 (latest)
  • Display: LG G1 via HDMI 2.1

Reproduction steps

Play a video suitable for testing HDR metadata/tone mapping.

I use the Mehanik HDR10 test patterns, specifically 02. White_Color clipping\04. White_900-4000nits-MaxCLL-4000-MDL-4000.mp4, which usually makes it obvious if the HDR metadata is being sent correctly or not.

Expected behavior

The HDR metadata is sent correctly. In the case of the test video mentioned above, a peak luminance of 4000 nits should be sent to the display; as a result the display should apply the corresponding tone mapping curve resulting in proper gradation across the band.

Actual behavior

The metadata appears to be sent incorrectly (i.e. the gradations disappear), even in full screen mode.

Additional information

Note that, strangely, the issue is not always perfectly reproducible. Most of the time mpv won't be able to get the metadata across, but once in a blue moon it actually works. It's not clear to me what triggers it.

At first I thought it could be triggered by using mpv after using another HDR-capable player first (e.g. VLC or madVR), but that doesn't seem to always be the case.

This smells like a OS or GPU driver bug, but I will point out that neither VLC nor madVR ever seem to get this wrong (as long as they are in full screen mode) - as far as I can tell only mpv is affected.

Log file

log.txt

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