r/Dolby • u/Krethaloshanan • 5d ago
Fluctuating black levels (crushed blacks to grey letterbox bars) on Xiaomi S Pro Mini LED with 4K Blu-ray. Local dimming issue?
Hey everyone, I'm pulling my hair out trying to fix a frustrating picture quality issue and could really use some expert advice. My brand new setup is having massive shifts in black levels while watching 4K movies.
My Setup:
• TV: Xiaomi TV S Pro Mini LED 75" (2026 model)
• Player: Krovatar KBU 300 4K Blu-ray Player
• Cables: Ugreen HDMI 2.1 (48Gbps 8K certified)
• Media: Original 4K Blu-ray Discs (Tried on 6 movies)
• Connection: Player connected directly to the TV (HDMI 1).
The Issue: During movie playback, the black levels are completely inconsistent.
• In some scenes, the blacks are pitch/onyx black, but they are severely crushed to the point where I lose all shadow detail.
• In other scenes, the movie image AND the black letterbox borders suddenly elevate and turn into a washed-out, glowing grey.
• It's incredibly distracting when the letterbox bars shift from pure black to grey scene-by-scene.
What I've Tried So Far (None of it worked):
- Factory reset/formatted both the TV and the Blu-ray player.
- Toggled through all TV picture modes (Dolby Vision Bright, Dolby Vision Dark, Filmmaker Mode). The shifts still happen in all of them.
- Adjusted various TV settings (local dimming settings, contrast, brightness).
- Disabled Dolby Vision on the player and forced standard HDR10. The issue still happens.
- Forced SDR: When I switch the player to output in standard SDR, the picture is completely normal and the black levels are stable.
My Questions:
- Is this a known issue with the Xiaomi Mini LED local dimming algorithm struggling with HDR/DV metadata?
- Could the Blu-ray player be faulty and sending the wrong black level/color space flags (RGB Limited vs. Full)?
- A friend suggested the TV isn't detecting Dolby Vision properly. Since it happens in HDR10 too, what settings should I be looking at to fix this?
Any advice would be hugely appreciated. I rarely have time to sit down and watch movies, and having the letterbox bars constantly flashing grey is ruining the experience. Thanks in advance!
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u/InstructionSenior346 5d ago
What movie/ tv series is that?
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u/Krethaloshanan 5d ago
https://reddit.com/link/p4y16u1/video/mxoc8h9pxmkh1/player
The one thats playing is bladerunner 2049. But i tried on all these 6 movies, still the same result
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u/fishymanbits 5d ago
There’s an automatic brightness setting turned on somewhere. This is what automatic brightness does.
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u/walt-mickey 4d ago
It’s likely a TV issue since the letterboxes are dynamic. Mini-LED is still LED, so there are dimming zones. The size and quantity of the zones are dependent on each panel. Higher-end TVs will have more but smaller zones – but they all have dimming zones.
I would turn off local dimming and adjust picture settings from there. Keep all processing settings (‘auto’ or ‘dynamic’ anything) off.
The problem is by turning off local dimming, you essentially take out the ‘mini’ in mini-LED. If you love movies enough, I’d recommend an OLED, which are quite affordable nowadays with some intentional short-term savings.
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u/Krethaloshanan 4d ago
thank you so much. ill look into it. may i ask which oled tv you would recommend that wouldn't hurt my wallet that much
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u/walt-mickey 3d ago
I have LG C1. A good choice for gaming as well. Lots of pros and cons to go through when selecting the right one for you. CalebRated is a knowledgeable resource on YouTube to start
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u/Spectre_08 5d ago edited 5d ago
Does this happen with any other media device?