API Reference

All types use the ERP_ / UERP_ / FERP_ prefix and are Blueprint-accessible.

UERP_STTSubsystem — the primary API

Speech-to-text is a machine-global concern (one local mic, one local player), so the primary entry point is a GameInstanceSubsystem you drive directly — no actor or component required. The backend auto-initializes from Project Settings at startup, so in most projects you just bind OnText and call StartListening().

UERP_STTSubsystem* STT = GetGameInstance()->GetSubsystem<UERP_STTSubsystem>();
STT->OnText.AddDynamic(this, &UMyThing::HandleTranscript);
STT->StartListening();

The Blueprint API exposes the same core session controls, text/result events, and VAD/queue diagnostics as C++. Click the image to inspect the complete graph.

Listening session

Member	Kind	Description
StartListening()	function → bool	Open the mic and begin transcribing
StopListening()	function	Stop (transcribes pending audio first)
IsListening()	pure → bool	Session active?
FlushUtterance()	function	Transcribe accumulated audio now
SetConfig(FERP_STTConfig)	function	Language + VAD tuning; effective immediately
GetConfig()	pure → FERP_STTConfig	Current session config
OnSTTResult	event FERP_STTResult	Each completed utterance (already filtered)
OnText	event FString	Neutral transcript text for gameplay or optional external integrations

Push-to-talk

Member	Description
SetPushToTalkMode(ERP_PushToTalkMode)	AlwaysOn / PushToTalk / PushToSilence
SetPushToTalkActive(bool)	Key down (true) / up (false); release also flushes
SetMuted(bool) / IsMuted()	Set or inspect mute without stopping the session
GetPushToTalkMode()	Inspect the authoritative capture mode

Backend & models

Member	Description
IsBackendInitialized() → bool	Model loaded and ready
InitializeBackend(Config) → bool	Load a model from an explicit backend config
InitializeBackendWithModelFile(FileName) → bool	Load a model by filename
OnBackendReady / OnBackendInitFailed	Backend load success / failure (message)
GetModelInfo() / GetMemoryUsage()	Loaded model description / footprint
GetModelsDirectory() / GetAvailableModelFiles()	Models folder / .bin files present
GetSupportedLanguages() → TArray<FString>	Language codes of the active backend
GetProcessingState() / GetLastError() / GetLastErrorMessage()	Diagnostics
GetPendingTranscriptionCount() → int32	Worker backlog (real-time detection)

UERP_STTComponent — optional wrapper

An optional thin convenience component that forwards to the subsystem and re-broadcasts its events. Use it for drop-in Blueprint setups. It owns nothing.

Member	Kind	Description
Config	property FERP_STTConfig	Pushed to the subsystem on StartListening
bAutoStartListening	property bool	Start on BeginPlay, stop on EndPlay
StartListening() / StopListening() / IsListening()		Forward to subsystem
FlushTranscription()	function	Forward to Subsystem::FlushUtterance
SetConfig() / GetConfig()		Config, pushed to subsystem
IsSTTReady() / GetProcessingState() / GetLastErrorMessage()	pure	Backend diagnostics
OnSTTResult	event FERP_STTResult	Re-broadcast from subsystem
OnText	event FString	Re-broadcast from subsystem

FERP_STTResult

Field	Type	Description
TranscribedText	FString	The recognized text
Confidence	float	0.0–1.0 (average token probability)
bIsFinal	bool	Always true with the Whisper backend (utterance-based)
ProcessingTimeMs	float	Inference time

FERP_STTConfig

Field	Type	Default	Description
LanguageCode	FString	en-US	Language, or auto to detect
MinConfidenceThreshold	float	0.5	Drop results below this
bUseVoiceActivityDetection	bool	true	Auto-segment speech into utterances; off = accumulate until FlushTranscription()/StopListening() (push-to-talk style)
VADActivationThreshold	float	0.008	Absolute speech-start floor; adaptive VAD may raise it above ambient noise
VADDeactivationThreshold	float	0.004	Absolute release floor (hysteresis); adaptive VAD may raise it
VADEnergySmoothing	float	0.35	EMA factor on the energy (lower = smoother)
SilenceTimeoutSeconds	float	1.5	Silence that ends an utterance
MinUtteranceSeconds	float	0.3	Discard shorter blips
MaxUtteranceSeconds	float	25	Split longer speech into segments
PreRollSeconds	float	0.4	Audio kept from before speech onset

UERP_STTSubsystem

GameInstanceSubsystem owning the shared backend and the background transcription worker. Auto-initializes from Project Settings at startup.

Member	Description
InitializeBackend(Config) → bool	Load a model from an explicit backend config
InitializeBackendWithModelFile(FileName) → bool	Load a model by filename from the models directory
ShutdownBackend()	Unload (joins the worker thread first)
IsBackendInitialized() → bool	Ready state
OnBackendReady	Event: backend finished loading
OnBackendInitFailed	Event FString: load failed (message for UI)
GetModelInfo() → FString	Loaded model description
GetModelsDirectory() → FString	Absolute path of Content/ElysListen/Models
GetAvailableModelFiles() → TArray<FString>	.bin files present on disk
GetSupportedLanguages() → TArray<FString>	Language codes of the active backend
GetMemoryUsage() → int64	Estimated model memory footprint
GetPendingTranscriptionCount() → int32	Jobs queued on the worker (backlog detection)
GetProcessingState() / GetLastError() / GetLastErrorMessage()	Backend diagnostics

UERP_AudioCaptureSubsystem

Lower-level microphone capture, fanned out to consumers. The STT subsystem is its main consumer; you normally don't touch this directly (drive push-to-talk through UERP_STTSubsystem instead). Capture uses the device's native format (queried from the hardware).

UERP_STTSettings (Project Settings → Elys Listen (STT))

Setting	Description
bEnableAudioCapture	Project-wide microphone kill-switch
bEnableSTT / STTBackend	Enable STT and select the bundled local Whisper backend
STTModelPath	Model file; stored project-relative, resolved by ResolveModelPath()
DefaultLanguageCode	Language used at auto-initialization
WorkerThreadCount	Inference threads (0 = auto)
STTModelCatalog	The model list shown in the downloader
bEnableVerboseLogging	Detailed VAD/transcription diagnostics