Audio Device Management¶

Aboleth STT provides runtime control over which microphone is used for speech capture. You can enumerate available audio input devices, switch between them, and respond to device changes -- all without restarting the STT system.

API Reference¶

Function	Description
`RefreshAudioDevices()`	Re-scan the system for available audio input devices
`GetAvailableAudioDevices()`	Get the cached list of devices (call `RefreshAudioDevices()` first)
`SetAudioDeviceByIndex(int32)`	Switch to a specific device by its index
`UseDefaultAudioDevice()`	Switch back to the OS default input device
`GetSelectedDeviceIndex()`	Get the index of the currently selected device (`INDEX_NONE` for default)
`GetSelectedDeviceInfo()`	Get full device info for the current selection

Enumerating Devices¶

Refresh the device list, then iterate to present options to the user:

C++Blueprint

UAbolethSTTSubsystem* STT = UAbolethSTTSubsystem::GetSTTSubsystem(this);

// Refresh the device list from the OS
STT->RefreshAudioDevices();

// Get all available input devices
TArray<FAudioDeviceInfo> Devices = STT->GetAvailableAudioDevices();

for (const FAudioDeviceInfo& Device : Devices)
{
    UE_LOG(LogTemp, Log, TEXT("[%d] %s (Channels: %d, Rate: %d, AEC: %s)"),
        Device.DeviceIndex,
        *Device.DeviceName,
        Device.InputChannels,
        Device.PreferredSampleRate,
        Device.bSupportsHardwareAEC ? TEXT("Yes") : TEXT("No"));
}

Call Refresh Audio Devices on the Subsystem, then Get Available Audio Devices to receive an array of FAudioDeviceInfo structs. Each struct contains the device name, index, channel count, sample rate, and whether hardware AEC is supported.

Switching Devices¶

C++Blueprint

UAbolethSTTSubsystem* STT = UAbolethSTTSubsystem::GetSTTSubsystem(this);

// Switch to device at index 2
bool bSuccess = STT->SetAudioDeviceByIndex(2);

// Switch back to OS default
STT->UseDefaultAudioDevice();

// Check what's currently selected
int32 CurrentIndex = STT->GetSelectedDeviceIndex();          // INDEX_NONE = default
FAudioDeviceInfo CurrentDevice = STT->GetSelectedDeviceInfo();

Call Set Audio Device By Index with the desired device index. Call Use Default Audio Device to revert to the OS default. Use Get Selected Device Index and Get Selected Device Info to query the current selection.

Changes take effect immediately

When you switch devices, the microphone capture component restarts automatically with the new device. There is no need to stop and restart listening manually. The pipeline returns to Idle and resumes listening on the new device within a few frames.

Device Info Struct¶

Each device is described by an FAudioDeviceInfo struct:

Field	Type	Description
`DeviceName`	`FString`	Human-readable device name
`DeviceId`	`FString`	System-level device identifier
`DeviceIndex`	`int32`	Index for use with `SetAudioDeviceByIndex()`
`InputChannels`	`int32`	Number of input channels
`PreferredSampleRate`	`int32`	Device's preferred sample rate
`bSupportsHardwareAEC`	`bool`	Whether the device has hardware acoustic echo cancellation

Events¶

Two delegates fire in response to device changes:

OnAudioDeviceChanged¶

Fires when the active audio device changes (after calling SetAudioDeviceByIndex() or UseDefaultAudioDevice()).

OnAudioDeviceChanged(FAudioDeviceInfo NewDevice)

OnAudioDevicesRefreshed¶

Fires when the device list is refreshed (after calling RefreshAudioDevices()). Use this to update a device selection UI.

OnAudioDevicesRefreshed()

C++Blueprint

// Bind device change events
STT->OnAudioDeviceChanged.AddDynamic(this, &AMyActor::HandleDeviceChanged);
STT->OnAudioDevicesRefreshed.AddDynamic(this, &AMyActor::HandleDevicesRefreshed);

void AMyActor::HandleDeviceChanged(const FAudioDeviceInfo& NewDevice)
{
    UE_LOG(LogTemp, Log, TEXT("Switched to: %s"), *NewDevice.DeviceName);
}

void AMyActor::HandleDevicesRefreshed()
{
    // Rebuild the device dropdown in your settings UI
    RebuildDeviceList(STT->GetAvailableAudioDevices());
}

Bind On Audio Device Changed and On Audio Devices Refreshed on the Subsystem or Listener Component to respond to device changes in your UI.