Flickering black band on LG DualUp display when HiDPI is enabled

[awcm0n]

When HiDPI is enabled, a flickering black band appears at the top of the screen when the mouse moves. It covers about a third of the menu bar.

BetterDisplay Version 3.2.2 Internal Pre-Release Build 36356
iMac M1 (2021)
LG DualUp 28MQ780-B 27.6" HDR Monitor connected via USB-C

Display Information
BetterDisplay Version 3.2.2 Internal Pre-Release Build 36356

LG SDQHD - Third-party external display - Connected

Identifiers
-----------
Serial number: B8E2
Vendor ID: 1E6D (GSM)
Model ID: 5BF6
Product name: LG SDQHD
Alphanumeric serial: 206NTXR1D330
Year of manufacture: 2022
Week of manufacture: 6
UUID: 19ECF3BE-7C4D-7484-0857-D6964E3302DB
Dimensions (unrotated): 470.05mm x 520.45mm
Registry location: IOService:/AppleARMPE/arm-io@10F00000/AppleT810xIO/dispext0@70000000/AppleCLCD2
Metal device: Apple M1
Platform: Apple Silicon
I2C service name: DCPAVServiceProxy
DDC messaging: Standard
CGDirectDisplayID: 2
Tag ID: 3
Configuration run ID: 57
First added: Dec 31, 2024 at 6:01:54 PM
Last detected: Jan 2, 2025 at 10:49:11 AM
Last undetected: Jan 2, 2025 at 10:49:08 AM

Capabilities
------------
Software control: Yes
Hardware control (Apple): No
Color table alteration capable: Yes
Potentially DDC compatible: Yes
Supports proper HiDPI: Yes
Supports changing orientation: Yes
Supports variable refresh rate: No
Supports XDR presets: No
Supports Color Profiles: Yes
XDR/HDR upscaling compatible: Yes
Supports HDR: Yes
Potential EDR: 1.0
Reference EDR: 1.0
Horizontal GPU resolution limit: 3,072 pixels HiDPI (6,144 pixels LoDPI)

Current Display Mode
--------------------
Mode number: 249
Logical width: 2304
Logical height: 2592
HiDPI: Yes
Pixel width: 4608
Pixel height: 5184
Bits per sample: 10
Samples per pixel: 3
Bits per pixel: 32
Pixel encoding: --RRRRRRRRRRGGGGGGGGGGBBBBBBBBBB��������������������������������
1:1 pixel mapped resolution: No
Default resolution: No
Refresh string: 60Hz
Variable refresh rate: No
Max refresh rate: 60
Min refresh rate: 60
Fixed-point refresh rate: 3,932,160 (interpreted as 60.000000)
Row bytes: 18432
Horizontal density: 249
Vertical density: 253
Flags: 00000003
Unsafe mode: No
Invalid mode: No

Current Display Mode (Connection Level)
---------------------------------------
Description:  2560 x 2880 RGB 10bit full
Dimensions: 2560 x 2880
Refresh Rate: 59.97999865934253
Variable Refresh Rate: No
Bit Depth: 10 bits per sample
Color Mode: RGBFullRange
YCbCr: No
HDR/SDR Mode: SDR
Color Gamut: gamut_SRGB
Virtual: No
Pixel Aspect Ratio: 1.0
Preferred Scale: 2

Preferred Display Mode (Connection Level)
-----------------------------------------
Description:  2560 x 2880 RGB 10bit full
Dimensions: 2560 x 2880
Refresh Rate: 59.97999865934253
Variable Refresh Rate: No
Bit Depth: 10 bits per sample
Color Mode: RGBFullRange
YCbCr: No
HDR/SDR Mode: SDR
Color Gamut: gamut_SRGB
Virtual: No
Pixel Aspect Ratio: 1.0
Preferred Scale: 2

Sidecar Configuration
---------------------
Name: LG SDQHD
Sidecar UUID: n/a
State: Unknown

Color Profile Configuration
---------------------------
Custom Profiles / 1: file:///Library/ColorSync/Profiles/Displays/iMac%20Calibrated.icc
Device Class: mntr
Device Description: LG SDQHD
Device Host Scope: kCFPreferencesCurrentHost
Device ID: <CFUUID 0x60000235f2c0> 19ECF3BE-7C4D-7484-0857-D6964E3302DB
Device User Scope: kCFPreferencesAnyUser
Factory Profiles / 1 / Device Mode Description: LG SDQHD
Factory Profiles / 1 / Device Profile URL: file:///Library/ColorSync/Profiles/Displays/LG%20SDQHD-19ECF3BE-7C4D-7484-0857-D6964E3302DB.icc
Factory Profiles / Device Default Profile ID: 1

Display Information
-------------------
Display Supports Rotation: 1 (Yes)
Display Is Exclusive: 0 (No)
Display Horizontal Image Size: 470
Display Supports Dynamic Geometry: 0 (No)
Display Blue Point X: 0.15
Display Product ID: 23,542
Display Year Manufacture: 2,022
Display Is Virtual Device: 0 (No)
Display Blue Point Y: 0.06
Slope Limit Gamma: 1 (Yes)
Display-icon: public.display
Display UUID: 19ECF3BE-7C4D-7484-0857-D6964E3302DB
Display Transport Type: 1 (Yes)
Display Is Air Play: 0 (No)
Display Product Name / Hr_ HR: LG SDQHD
Display Product Name / Ko_ KR: LG SDQHD
Display Product Name / Nb_ NO: LG SDQHD
Display Product Name / Id: LG SDQHD
Display Product Name / Hu_ HU: LG SDQHD
Display Product Name / Cs_ CZ: LG SDQHD
Display Product Name / Sl_ SI: LG SDQHD
Display Product Name / Da_ DK: LG SDQHD
Display Product Name / Uk_ UA: LG SDQHD
Display Product Name / Fr_ CA: LG SDQHD
Display Product Name / It_ IT: LG SDQHD
Display Product Name / Zh_ TW: LG SDQHD
Display Product Name / Ar: LG SDQHD
Display Product Name / He_ IL: LG SDQHD
Display Product Name / Es_ ES: LG SDQHD
Display Product Name / Nl_ NL: LG SDQHD
Display Product Name / Fi_ FI: LG SDQHD
Display Product Name / Ro_ RO: LG SDQHD
Display Product Name / Vi_ VN: LG SDQHD
Display Product Name / Sk_ SK: LG SDQHD
Display Product Name / Zh_ CN: LG SDQHD
Display Product Name / Ru_ RU: LG SDQHD
Display Product Name / En_ GB: LG SDQHD
Display Product Name / Fr_ FR: LG SDQHD
Display Product Name / Ms: LG SDQHD
Display Product Name / Hi_ IN: LG SDQHD
Display Product Name / Th_ TH: LG SDQHD
Display Product Name / Ca_ ES: LG SDQHD
Display Product Name / Es_ XL: LG SDQHD
Display Product Name / En_ AU: LG SDQHD
Display Product Name / De_ DE: LG SDQHD
Display Product Name / En_ US: LG SDQHD
Display Product Name / Pt_ BR: LG SDQHD
Display Product Name / Pl_ PL: LG SDQHD
Display Product Name / El_ GR: LG SDQHD
Display Product Name / Sv_ SE: LG SDQHD
Display Product Name / Tr_ TR: LG SDQHD
Display Product Name / Ja_ JP: LG SDQHD
Display Product Name / Pt_ PT: LG SDQHD
Display Green Point X: 0.3
Display Vertical Image Size: 520
Display White Gamma: 2.2
Display Is SLVD Exclusive: 0 (No)
Display Serial Number: 47,330
Display Pixel Width: 2,560
Display Week Manufacture: 6
Display Green Point Y: 0.6
IO Display Is Digital: 1 (Yes)
IO Display Location: IOService:/AppleARMPE/arm-io@10F00000/AppleT810xIO/dispext0@70000000/AppleCLCD2
Display Pixel Height: 2,880
Display ID: 2
Display White Point X: 0.3127
Display Is Presentation Display: 0 (No)
Display Is Presentation Mode Enabled: 0 (No)
Display DPI Cutoff: 300
Display Vendor ID: 7,789
Display CA Device Name: external-0
Display Dynamic Geometry Enabled: 0 (No)
Display White Point Y: 0.329
Display Is DFR: 0 (No)
Display Supports Underscan: 0 (No)
Display Red Point X: 0.64
Display Bundle URL: /System/Library/Displays
Display Red Point Y: 0.33
Aspect Ratio: 9
Chromaticity / Blue / X: 9,472
Chromaticity / Blue / Y: 3,840
Chromaticity / Green / X: 16,960
Chromaticity / Green / Y: 43,776
Chromaticity / Red / X: 44,800
Chromaticity / Red / Y: 20,352
Continuous Frequency Support: None
Default Color Space Is SRGB: 1 (Yes)
Default White Point / Gamma: 144,179
Default White Point / X: 20,544
Default White Point / Y: 21,568
Has HDMI Legacy EDID: 0 (No)
Luminance / Max: 19,357,056
Luminance / Max Frame Average: 19,357,056
Luminance / Min: 19,529
Max Horizontal Image Size: 47
Max Vertical Image Size: 52
Maximum Refresh Rate: 61
Maximum Variable Refresh Rate: 3,997,696
Minimum Refresh Rate: 59
Minimum Variable Refresh Rate: 3,866,624
Native Format Horizontal Pixels: 2,560
Native Format Vertical Pixels: 2,880
Port ID: 0 (No)
Precise Aspect Ratio: 59,234
Product Attributes / Alphanumeric Serial Number: 206NTXR1D330
Product Attributes / Legacy Manufacturer ID: 7,789
Product Attributes / Manufacturer ID: GSM
Product Attributes / Product ID: 23,542
Product Attributes / Product Name: LG SDQHD
Product Attributes / Serial Number: 47,330
Product Attributes / Week Of Manufacture: 6
Product Attributes / Year Of Manufacture: 2,022
Supports Active Off: 1 (Yes)
Supports BT 2020 RGB: 512
Supports BT 2020 YCC: 128
Supports BT 2020c YCC: 0 (No)
Supports HDR Gamma EOTF: 0 (No)
Supports HDR Static Metadata Type 1: 1 (Yes)
Supports HLGEOTF: 0 (No)
Supports PQEOTF: 1 (Yes)
Supports Standby: 0 (No)
Supports Suspend: 0 (No)
Supports Variable Refresh Rate: 0 (No)
White Points - 1 / Gamma: 144,179
White Points - 1 / X: 20,544
White Points - 1 / Y: 21,568
Allows Virtual Modes: 0 (No)
Bounds: NSRect: {{0, 0}, {4608, 5184}}
Cloned: 0 (No)
Cloning: 0 (No)
Cloning Supported: 0 (No)
Color Mode: auto
Connection Seed: 135
Container Id: 
Current Orientation: rot0
Device Name: external-0
Display Id: 2
Display Type: 1 (Yes)
External: 1 (Yes)
External Display Attributes / Bt 2020 YCC: 2
External Display Attributes / Dolby Vision: 0 (No)
External Display Attributes / Hdr Static Metadata Type 1: 2
External Display Attributes / Legacy HDMIEDID: 0 (No)
External Display Attributes / Manufacturer ID: 7,789
External Display Attributes / Pq EOTF: 2
External Display Attributes / Product ID: 23,542
External Display Attributes / Serial Number: 47,330
External Display Attributes / Week Of Manufacture: 6
External Display Attributes / Year Of Manufacture: 2,022
Frame: NSRect: {{0, 0}, {2560, 2880}}
Has Native Frame Rate Request: 0 (No)
Heartbeat Rate: 0.01666666666666667
Is Reference: 0 (No)
Is Reference Limited: 0 (No)
Latency: 0 (No)
Link Quality: -1
Logical Scale: NSSize: {1.7999999523162842, 1.7999999523162842}
Maximum Logical Scale: 1.600000023841858
Minimum Frame Duration: 1 (Yes)
Minimum Logical Scale: 0.25
Name: External
Native Orientation: rot0
Native Size: NSSize: {2560, 2880}
Od LUT Version: 0 (No)
Overscan Adjustment: none
Overscan Amount: 0.8999999761581421
Overscan Amounts: NSSize: {0.89999997615814209, 0.89999997615814209}
Overscanned: 0 (No)
Physical Size: NSSize: {18.503936767578125, 20.472440719604492}
Point Scale: 1 (Yes)
Process Id: 0 (No)
Product Name: LG SDQHD
Refresh Rate: 0.01666666666666667
Safe Bounds: NSRect: {{0, 0}, {4608, 5184}}
Seed: 232
Supported: 1 (Yes)
Supports Extended Colors: 0 (No)
Tag: 0 (No)
Transport Type: dp
Unique Id: 1E6DF65B-0000-0000-0620-0104B52F3478

[waydabber]

Does this happen with all HiDPI resolutions and refresh rates and both in HDR and SDR mode? If native mode is used, then this might be an Apple DCP issue related to the unusual resolution of the display, not a specific app bug.

[awcm0n]

In the meantime I realized it does not happen with 80% scaling in SDR mode (which is a setting I'm happy with) but it happens with 81% to 99%. It also does not happen in HDR mode but picture quality is atrocious.