Force Mac output colour in RGB instead of YPbPr

Introduction

Some of the people said RGB color space is better than YPbPr color space. By default, mac is using the YPbPr color format. To use RGB color format, we need to modify the EDID display setting.

Here is my computer and monitor model.

Mac: Macbook pro 2018 – macOS 11.1
Monitor: Dell U2720Q

Procedure

Follow this guide.

sudo mkdir -p /Library/Displays/Contents/Resources/Overrides
cd /Library/Displays/Contents/Resources/Overrides
sudo curl -O https://gist.githubusercontent.com/ejdyksen/8302862/raw/patch-edid.rb
sudo ruby patch-edid.rb

Then, restart your Mac.

After that, your display name will become Display with forced RGB mode (EDID override) at System Information

Reference

patch-edid.rb

A script to fix EDID problems on external monitors in macOS.

Instructions

1. Connect only the problem display.

2. Create this directory structure (if it doesn’t already exist):

   sudo mkdir -p /Library/Displays/Contents/Resources/Overrides

3. Download this ruby script in that directory:

   cd /Library/Displays/Contents/Resources/Overrides
   sudo curl -O https://gist.githubusercontent.com/ejdyksen/8302862/raw/patch-edid.rb

   Note: You may want to use adaugherity’s version of the script instead.

4. Run the script we just downloaded (as root again). This creates a new display override plist file.

   cd /Library/Displays/Contents/Resources/Overrides
   sudo ruby patch-edid.rb

5. Unplug and replug in the problem display.

Additional reading/acknowledgements

• The original forum thread
• An improved version of the script by adaugherity
• An explaination of the problem from Atomic Object’s blog
• Thanks so much to @stackrainbow for pointing out that this can be done without disabling SIP.
• This version appears to work in Catalina and Big Sur. See earlier revisions for what worked (with disabling SIP) in earlier versions of macOS, which require the override plist to be in a different directory.

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patch-edid.md

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	#!/usr/bin/ruby
	# Create display override file to force Mac OS X to use RGB mode for Display
	# see http://embdev.net/topic/284710
	#
	# Update 2013-06-24: added -w0 option to prevent truncated lines
	require 'base64'
	data=`ioreg -l -w0 -d0 -r -c AppleDisplay`
	edid_hex=data.match(/IODisplayEDID.*?<([a-z0-9]+)>/i)[1]
	vendorid=data.match(/DisplayVendorID.*?([0-9]+)/i)[1].to_i
	productid=data.match(/DisplayProductID.*?([0-9]+)/i)[1].to_i
	puts "found display: vendorid #{vendorid}, productid #{productid}, EDID:\n#{edid_hex}"
	bytes=edid_hex.scan(/../).map{|x|Integer("0x#{x}")}.flatten
	puts "Setting color support to RGB 4:4:4 only"
	bytes[24] &= ~(0b11000)
	puts "Number of extension blocks: #{bytes[126]}"
	puts "removing extension block"
	bytes = bytes[0..127]
	bytes[126] = 0
	bytes[127] = (0x100–(bytes[0..126].reduce(:+) % 256)) % 256
	puts
	puts "Recalculated checksum: 0x%x" % bytes[127]
	puts "new EDID:\n#{bytes.map{|b|"%02X"%b}.join}"
	Dir.mkdir("DisplayVendorID-%x" % vendorid) rescue nil
	f = File.open("DisplayVendorID-%x/DisplayProductID-%x" % [vendorid, productid], 'w')
	f.write '<?xml version="1.0" encoding="UTF-8"?>
	<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"&gt;
	<plist version="1.0">'
	f.write "
	<dict>
	<key>DisplayProductName</key>
	<string>Display with forced RGB mode (EDID override)</string>
	<key>IODisplayEDID</key>
	<data>#{Base64.encode64(bytes.pack('C*'))}</data>
	<key>DisplayVendorID</key>
	<integer>#{vendorid}</integer>
	<key>DisplayProductID</key>
	<integer>#{productid}</integer>
	</dict>
	</plist>"
	f.close

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patch-edid.rb

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Fixing the External Monitor Color Problem with My 2018 MacBook Pro

https://forums.macrumors.com/threads/m1-mac-external-display-fuzzy-fonts-colors-ypbpr-vs-rgb.2276345/