Mac Display Volume

中文文档

Mac Display Volume lets macOS control an external display's audio volume like a normal speaker.

Some displays expose HDMI, DisplayPort, or USB-C audio to macOS as a fixed-volume output device. The keyboard volume keys and menu bar volume slider may be disabled, or they may change the display's own hardware volume. If the same display is also used with Windows, a game console, or another device, that shared hardware volume can become annoying quickly.

Mac Display Volume creates a virtual audio output device on the Mac:

macOS apps
  -> Mac Display Volume
  -> software volume control
  -> your real display speaker

Set the system output to Mac Display Volume, then choose the real display audio device as its target. macOS volume changes are applied in software before the audio is forwarded to the display. The display's own hardware volume can stay fixed, so changing volume on macOS does not affect the same monitor when it is used from another machine.

Who It Is For

• You use an external display with built-in speakers or audio output.
• macOS cannot adjust that display's volume normally.
• You want volume changes to affect only the current Mac.
• The same display is also used by Windows, a game console, or another device.

Features

• Creates a macOS virtual audio output device.
• Supports system volume and mute controls.
• Forwards audio to the real display audio device with low latency.
• Provides a menu bar app for choosing the target output device.
• Can switch the default output to the virtual device.
• Keeps the display's hardware volume unchanged.

Requirements

• macOS 15 or newer.
• Apple Silicon Mac.
• An external display with audio output.

Installation

The current version is intended for local build and installation. Xcode 26 or newer is required.

Scripts/install-local.sh

The install script builds the app and HAL driver, then installs them to:

• /Applications/Mac Display Volume.app
• /Library/Audio/Plug-Ins/HAL/MacDisplayVolumeAudio.driver

You may be asked for an administrator password during installation. If the new audio device does not appear immediately after installation, restart CoreAudio. If it still does not appear, rebooting the Mac usually clears stale CoreAudio caches and old driver helper processes.

Usage

1. Open /Applications/Mac Display Volume.app.
2. Choose the real display audio device, for example P275MV.
3. Click Apply Driver Config.
4. Click Use Virtual Output.
5. Keep the display's own hardware volume fixed.

After that, use the keyboard volume keys, the menu bar volume slider, or System Settings to control the volume of Mac Display Volume.

Notes

• The target output device must support 48 kHz.
• Do not set Mac Display Volume itself as the target device.
• If audio latency starts accumulating, use Reset Relay first.
• If CoreAudio gets into a bad state, use Restart coreaudiod or reboot the Mac.

Driver Smoke Test

Run the HAL driver smoke test inside a disposable macOS VM:

Scripts/vm-smoke-test.sh

The script builds and installs the driver, restarts coreaudiod, verifies system_profiler enumeration and coreaudiod bundle loading, runs DriverProbe, and uninstalls the driver by default.

Uninstall

Scripts/uninstall-local.sh

The uninstall script removes the app and HAL driver, then restarts CoreAudio.

How It Works

Mac Display Volume has two parts:

• SwiftUI menu bar app: selects the target device, applies configuration, and switches the default output.
• CoreAudio HAL driver: exposes the virtual output device, applies software volume, and forwards audio.

The driver uses a fixed-size relay buffer. When too much audio is queued, it drops the oldest frames and re-anchors the timeline to avoid accumulating multi-second latency.

License

Apache License 2.0.