m1ddc

This little tool controls external displays (connected via USB-C/DisplayPort Alt Mode) using DDC/CI on Apple Silicon Macs. Useful to embed in various scripts.

For a much more advanced CLI solution check out BetterDisplay's CLI capabilities.

Warning

Please note that this tool does not support the built-in HDMI port of M1 and entry level M2 Macs. This tool does not support Intel Macs. You can use BetterDisplay for free DDC control on all Macs and all ports.

Prerequisites

Note

You need clang from Apple's Command Line Tools (installs automatically if not present).

Installation

After download, enter (in Terminal):

make

You can then run the app by entering:

./m1ddc [options]

Usage examples

# Sets contrast to 5 on default display
m1ddc set contrast 5
# Returns current luminance ("brightness") on default display
m1ddc get luminance
# Sets red gain to 90
m1ddc set red 90
# Decreases volume by 10 on default display
m1ddc chg volume -10
# Lists displays
m1ddc display list
# Sets volume to 50 on Display 1
m1ddc display 1 set volume 50
# Sets input to DisplayPort 1 on display with UUID '10ACB8A0-0000-0000-1419-0104A2435078'
m1ddc display 10ACB8A0-0000-0000-1419-0104A2435078 set input 15`

Available commands

 set luminance n         - Sets luminance (brightness) to n, where n is a number between 0 and the maximum value (usually 100).
     contrast n          - Sets contrast to n, where n is a number between 0 and the maximum value (usually 100).
     (red,green,blue) n  - Sets selected color channel gain to n, where n is a number between 0 and the maximum value (usually 100).
     volume n            - Sets volume to n, where n is a number between 0 and the maximum value (usually 100).
     input n             - Sets input source to n, common values include:
                           DisplayPort 1: 15, DisplayPort 2: 16, HDMI 1: 17, HDMI 2: 18, USB-C: 27.
     input-alt n         - Sets input source to n (using alternate addressing, as used by LG), common values include:
                           DisplayPort 1: 208, DisplayPort 2: 209, HDMI 1: 144, HDMI 2: 145, USB-C / DP 3: 210.

     mute on             - Sets mute on (you can use 1 instead of 'on')
     mute off            - Sets mute off (you can use 2 instead of 'off')

     pbp n               - Switches PIP/PBP on certain Dell screens (e.g. U3421W), possible values:
                           off: 0, small window: 33, large window: 34, 50/50 split: 36, 26/74 split: 43, 74/26 split: 44.
     pbp-input n         - Sets second PIP/PBP input on certain Dell screens, possible values:
                           DisplayPort 1: 15, DisplayPort 2: 16, HDMI 1: 17, HDMI 2: 18.

 get luminance           - Returns current luminance (if supported by the display).
     contrast            - Returns current contrast (if supported by the display).
     (red,green,blue)    - Returns current color gain (if supported by the display).
     volume              - Returns current volume (if supported by the display).

 max luminance           - Returns maximum luminance (if supported by the display, usually 100).
     contrast            - Returns maximum contrast (if supported by the display, usually 100).
     (red,green,blue)    - Returns maximum color gain (if supported by the display, usually 100).
     volume              - Returns maximum volume (if supported by the display, usually 100).

 chg luminance n         - Changes luminance by n and returns the current value (requires current and max reading support).
     contrast n          - Changes contrast by n and returns the current value (requires current and max reading support).
     (red,green,blue) n  - Changes color gain by n and returns the current value (requires current and max reading support).
     volume n            - Changes volume by n and returns the current value (requires current and max reading support).

 display list [detailed] - Lists displays. If `detailed` is provided, prints display extended attributes.
         n               - Chooses which display to control (use number 1, 2 etc.)
         (method=)<id>   - Chooses which display to control using the number using a specific identification method. (If not set, it defaults to `uuid`).
                           Possible values for `method` are:
                           'id':    <display_id>
                           'uuid':  <system_uuid>  *Default
                           'edid':  <edid_uuid>
                           'seid':  <alphnum_serial>:<edid_uuid>
                           'basic': <vendor>:<model>:<serial>
                           'ext':   <vendor>:<model>:<serial>:<manufacturer>:<alphnum_serial>:<product_name>
                           'full':  <vendor>:<model>:<serial>:<manufacturer>:<alphnum_serial>:<product_name>:<io_location>

Tip

You can also use 'l', 'v' instead of 'luminance', 'volume' etc.

Identification methods

The following display identification methods are supported, and corresponds to the following strings

Method	Related display attributes
id	<display_id>
uuid	<system_uuid>
edid	<edid_uuid>
seid	<alphnum_serial>:<edid_uuid>
basic	<vendor>:<model>:<serial>
ext	<vendor>:<model>:<serial>:<manufacturer>:<alphnum_serial>:<product_name>
full	<vendor>:<model>:<serial>:<manufacturer>:<alphnum_serial>:<product_name>:<io_location>

Tip

Corresponding display attributes can be obtained using the display list detailed command

Example use in a script

Check out the following hammerspoon script.

This script allows you to control the volume of your external Display' brightness, contrast and volume via DDC (if you use an M1 Mac) using m1ddc and also control your Yamaha AV Receiver through network. The script listens to the standard Apple keyboard media keys and shos the standard macOS Brightness and Volume OSDs via uses showosd :

https://gist.github.com/waydabber/3241fc146cef65131a42ce30e4b6eab7

BetterDisplay

If you like m1ddc, you'll like BetterDisplay even better!

BetterDisplay's CLI documentation: https://github.com/waydabber/BetterDisplay/wiki/Integration-features,-CLI

If you need a complete Swift implementation for DDC control on Apple Silicon macs, you can take a look at AppleSiliconDDC which is a complete self-contained library I made for BetterDisplay (note: some features and M1 HDMI support is missing from the open source code) and MonitorControl.

Thanks

Thanks to @tao-j @alin23, @ybbond

Enjoy!