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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.