Windows MIDI Audio Mixer Controller

A skill for working with Mideej, a .NET 9.0 WPF application that transforms MIDI controllers into Windows audio mixers, allowing control of application volumes, mute/solo functions, and audio monitoring via MIDI faders, knobs, and buttons.

Project Overview

Mideej is a fully functional MIDI-based Windows audio mixer targeting .NET 9.0. Users can control Windows application volumes (Spotify, browsers, games, etc.) using physical MIDI controllers with real-time visual feedback.

**Core Features:**

Technology Stack

Instructions

1. Understanding the Architecture

Before making changes, familiarize yourself with the layered architecture:

**MIDI Input Layer** (`Services/MidiService.cs`):

**Mapping Layer** (`ViewModels/MainWindowViewModel.cs`):

**Audio Control Layer** (`Services/AudioSessionManager.cs`):

**UI Layer**:

2. Common Development Tasks

#### Building and Running

```bash

Build the project

dotnet build

Run the application

dotnet run

Build for release

dotnet build -c Release

Clean build artifacts

dotnet clean

Restore dependencies

dotnet restore

```

#### Adding New MIDI Mappings

1. Update `MidiService.cs` to handle new MIDI message types

2. Extend `MainWindowViewModel.cs` to process new mapping types

3. Update `ConfigurationService.cs` to persist new mapping data

4. Add UI controls if needed in `ChannelControl.xaml`

#### Creating New UI Controls

1. Add XAML file to `Controls/` folder

2. Follow existing patterns (e.g., `ChannelControl.xaml`)

3. Use SkiaSharp for custom graphics rendering

4. Bind to ViewModel properties using MVVM pattern

#### Extending Audio Processing

1. Modify `AudioSessionManager.cs` for new audio functionality

2. Handle NAudio exceptions (sessions can become stale)

3. Update UI throttling to maintain performance (30ms refresh for VU meters)

4. Test with multiple audio applications running

3. Working with MIDI

#### Supported MIDI Message Types

#### Mackie Control Protocol

The application supports Mackie Control-compatible devices:

#### Testing MIDI Functionality

1. Connect a MIDI device to the system

2. Select the device from the dropdown in the application

3. Click the gear icon on a channel to enter learning mode

4. Move a MIDI control (fader, knob, or button)

5. Verify the mapping was created and the control affects the channel

6. Check that LED feedback or motorized faders respond correctly

4. Configuration Management

#### User Configuration Location

`%APPDATA%/Mideej/`

#### Controller Presets

`ControllerPresets/` directory contains pre-configured mappings:

```json

{

"ControllerName": "Your Controller",

"Channels": [

{

"ChannelNumber": 1,

"FaderCC": 0,

"MuteCC": 16,

"SoloCC": 32

}

]

}

```

To add a new preset:

1. Create a JSON file in `ControllerPresets/`

2. Follow the structure shown above

3. Document MIDI CC numbers for your controller

4. Test all mappings with the physical device

5. Audio Session Management

**Key Considerations:**

**Handling Session Changes:**

```csharp

// Sessions can become invalid - always check and handle exceptions

try {

audioSession.SimpleAudioVolume.Volume = newVolume;

} catch (COMException) {

// Session no longer exists - refresh session list

RefreshAudioSessions();

}

```

6. Code Style and Patterns

7. Current Implementation Status

✅ **Fully Working:**

🚧 **Partially Implemented:**

8. Important Files Reference

| File | Purpose |

|------|---------|

| `Services/MidiService.cs` | MIDI device management and message routing |

| `Services/AudioSessionManager.cs` | Windows audio session control |

| `Services/ConfigurationService.cs` | Settings and mapping persistence |

| `ViewModels/MainWindowViewModel.cs` | Main application logic and MIDI mapping |

| `ViewModels/ChannelViewModel.cs` | Individual channel state |

| `Controls/ChannelControl.xaml` | Channel strip UI component |

| `Controls/VuMeter.cs` | Real-time audio level visualization |

| `MainWindow.xaml` | Main application window |

| `Views/SessionAssignmentWindow.xaml` | Audio session assignment dialog |

9. Debugging Tips

Constraints

Examples

Adding a New Channel Control Type

```csharp

// 1. Add to ChannelViewModel.cs

[ObservableProperty]

private double _panPosition = 0.5;

// 2. Update MainWindowViewModel.cs MIDI handler

private void HandlePanControl(int channel, int value) {

var channelVm = Channels[channel - 1];

channelVm.PanPosition = value / 127.0; // Normalize 0-127 to 0-1

}

// 3. Add to ChannelControl.xaml

<Slider Value="{Binding PanPosition}" Minimum="0" Maximum="1" />

```

Creating a Custom Controller Preset

```json

{

"ControllerName": "Behringer X-Touch Mini",

"Channels": [

{

"ChannelNumber": 1,

"FaderCC": 0,

"MuteCC": 8,

"SoloCC": 16,

"SelectCC": 24

},

{

"ChannelNumber": 2,

"FaderCC": 1,

"MuteCC": 9,

"SoloCC": 17,

"SelectCC": 25

}

]

}

```

Handling Audio Session Changes

```csharp

// In AudioSessionManager.cs

public void RefreshSessions() {

var sessions = _sessionEnumerator.GetSessions();

foreach (var session in sessions) {

try {

var processId = session.GetProcessID;

var displayName = session.DisplayName;

// Cache session info

_sessionCache[processId] = new SessionInfo {

DisplayName = displayName,

Session = session

};

} catch (Exception ex) {

// Session might have closed during enumeration

Debug.WriteLine($"Session enumeration error: {ex.Message}");

}

}

}

```