AudioDeviceMonitor

Delphi component for monitoring audio device changes using Windows Core Audio API. Detects changes like switching from PC speakers to headphones.

Enhanced Version - What's New

Event Filtering System

• Duplicate Event Prevention: Filters multiple events for same device change
• Configurable Timeout: EventFilterTimeout property (default 500ms)
• Smart Detection: Only triggers on actual device changes, not Windows internal events

Error Handling

• HRESULT checks for all COM calls
• Exception handling and error logging
• LastError property for error tracking
• Initialize function for safe startup

Thread Safety

• UI events run on main thread (TThread.Queue)
• Crash protection in COM callbacks
• Safe event calling mechanism

Enhanced Event System

• OnDefaultDeviceChanged: Default device switched
• OnDeviceAdded: New device added
• OnDeviceRemoved: Device removed
• OnDeviceStateChanged: Device state changed
• OnPropertyValueChanged: Device properties changed
• OnAnyDeviceChanged: Any device change

Detailed Device Information

• TAudioDeviceInfo struct with rich device info
• Device friendly name retrieval
• Device ID, Flow, Role, State information
• Default device detection

New Public Methods

• GetCurrentDefaultDevice(): Get current default device
• GetAllAudioDevices(): List all audio devices
• IsDeviceActive(): Check device active status
• Initialize(): Manual initialization

Helper Functions

• DataFlowToString(): Convert Render/Capture to string
• RoleToString(): Console/Multimedia/Communications info
• DeviceStateToString(): Active/Disabled/Unplugged states

Memory Management

• PropVariant cleanup
• Proper cleanup for COM objects
• CoTaskMemFree to prevent memory leaks

Constants and Definitions

• Device state constants (DEVICE_STATE_ACTIVE etc.)
• Property key definitions (PKEY_Device_FriendlyName)
• PropVariant type constants (VT_LPWSTR etc.)

Usage

AudioMonitor := TAudioDeviceMonitor.Create(Self);
AudioMonitor.OnDefaultDeviceChanged := MyDeviceChangeHandler;
AudioMonitor.EventFilterTimeout := 300; // Optional: 300ms filter timeout

procedure TForm1.MyDeviceChangeHandler(Sender: TObject; const DeviceInfo: TAudioDeviceInfo);
begin
  ShowMessage('Audio device changed: ' + DeviceInfo.DeviceName);
end;

Key Improvements Over Original

The enhanced version provides better reliability for detecting audio device changes like switching from speakers to headphones, with proper error handling, thread-safe event notifications, and intelligent event filtering to prevent duplicate notifications.