The ProjectM Audio Receiver is an application designed for the Raspberry Pi that makes use of the projectM music visualization library, to react from an audio source of the users choosing.
The core components of the application will:
- Handle SDL rendering window
- Initialize projectM using a custom wrapper
- Capture SDL audio and route PCM data to projectM
- Listen for SDL mouse/keyboard/gamepad/window events for user controlled actions and window focus mgmt (if using Raspberry Pi lite OS evdev is used to monitor keyboard/mouse events)
The core controllers of the application will:
- Enforce the display resolution if running the Raspberry Pi desktop OS (Otherwise fullscreen exclusive mode is used for Raspberry Pi lite OS)
- Manage audio routing to ensure the device used to direct PCM audio data to projectM library receives all audio, while also ensuring any device you add for both input and output are routed accordingly so you don't have to manage it yourself.
- Manage audio plugin applications as defined in config. Currently projectM Audio Receiver has installation instructions for Bluetooth A2DP, AirPlay, Spotify Connect, and Plexamp.
The obvious purpose for this is to have visualizations react to sound. That said there are various use cases for implementation.
- Music player:
- Add DAC/ADC board for an analog input (e.g. HiFiBerry DAC+ ADC)
- Add DAC/DSP board for a digital input (e.g. HiFiBerry DAC+ DSP)
- Use Bluetooth A2DP, AirPlay, Spotify Connect, or Plexamp to "cast" to your device
- Store music in a local directory or use a usb drive of media and enable the "audio listener" in the projectMAR config file
- Monitoring Ambient Sound:
- Add a USB microphone to capture sound for visualizing
- Raspberry Pi OS Bookworm:
- Desktop OS (labwc, wayfire, and x11 are all supported)
- Lite OS
- Raspberry Pi
- Raspberry Pi 4 *This will only work with a reduced resolution and fps
- Raspberry Pi 5
- 5v/5A USB-C Power Supply
- SD Card (I recommend the SanDisk 32GB Extreme PRO microSD)
- Case with active cooling (The following are my recommendations)
- Hifiberry Steel case for RP5 w/active cooling and w/DAC+ ADC card for analog input/output
- Argon NEO 5 BRED Case for Raspberry Pi 5 with built-in fan
- HDMI Cable with Micro HDMI adapter or Micro HDMI to HDMI cable
- Input device of your choosing (You can always use built in Bluetooth; just know there is potential for interference with the built in card)
- USB Microphone
- USB Line in/Aux
- DAC/ADC
For both manual and automated script installation see SETUP.md.
This document describes how keyboard, controller, and window input events are handled in the application.
Handles key presses, with support for modifier keys like Ctrl.
Ctrl(either left or right) enables certain shortcut actions when combined with other keys.
| Key | With Ctrl? | Action |
|---|---|---|
F |
✅ | Toggle fullscreen mode |
N |
❌ | Load next preset |
P |
❌ | Load previous preset |
Q |
✅ | Exit the application |
Y |
✅ | Toggle playlist shuffle mode |
Delete |
❌ | Delete current preset |
Space |
❌ | Toggle preset lock |
Escape |
❌ | Toggle fullscreen mode |
Arrow Up |
❌ | Increase beat sensitivity (+0.1) |
Arrow Down |
❌ | Decrease beat sensitivity (−0.1) |
Handles analog stick and trigger inputs. Uses a deadzone threshold to avoid accidental movements.
| Axis | Condition | Action |
|---|---|---|
| Left Stick X / Trigger Left | Left / Pressed | Load previous preset |
| Left Stick X / Trigger Right | Right / Pressed | Load next preset |
| Left Stick Y | Up | Increase beat sensitivity (+0.1) |
| Left Stick Y | Down | Decrease beat sensitivity (−0.1) |
Handles digital controller buttons such as D-Pad and stick clicks.
| Button | Action |
|---|---|
| Left Stick Click / Right Stick Click | Toggle preset lock |
| D-Pad Up | Increase beat sensitivity (+0.1) |
| D-Pad Down | Decrease beat sensitivity (−0.1) |
| D-Pad Left | Load previous preset |
| D-Pad Right | Load next preset |
Handles SDL window-related system events.
| Event Type | Action |
|---|---|
SDL_WINDOWEVENT_CLOSE |
Exit the application |
SDL_WINDOWEVENT_RESIZED / SIZE_CHANGED |
Update internal rendering dimensions |
SDL_WINDOWEVENT_HIDDEN / MINIMIZED |
Restore and show the window |
SDL_WINDOWEVENT_FOCUS_LOST |
Log focus loss |
SDL_WINDOWEVENT_FOCUS_GAINED |
Log focus gain |