ULCKService (Unreal) - LCK Documentation

What Problem Does This Solve?

ULCKService is your main entry point for LCK functionality:

Start/stop/pause/resume recording
Configure recording resolution, framerate, and bitrate
Control microphone audio capture
Take photos
Monitor recording state and errors

Instead of interacting with low-level subsystems, you use this high-level service that handles the complexity for you.

When to Use This

Use ULCKService when:

Building custom recording UI
Implementing record buttons, settings menus
Controlling recording from gameplay code
Integrating recording into your game flow

Don’t use this directly if: You’re using the default LCK Tablet UI—it already handles everything.

Accessing the Service

From C++

ULCKSubsystem* Subsystem = GetWorld()->GetSubsystem<ULCKSubsystem>();
if (Subsystem)
{
    ULCKService* Service = Subsystem->GetService();
    // Use service...
}

From Blueprint

UFUNCTION(BlueprintCallable, Category = "LCK")
ULCKService* GetLCKService()
{
    if (UWorld* World = GetWorld())
    {
        if (ULCKSubsystem* Subsystem = World->GetSubsystem<ULCKSubsystem>())
        {
            return Subsystem->GetService();
        }
    }
    return nullptr;
}

Blueprint usage: Blueprint Get Service

Recording Methods

StartRecording / StopRecording

// Start recording — returns true if recording started successfully
bool bSuccess = Service->StartRecording();
if (!bSuccess)
{
    UE_LOG(LogLCK, Error, TEXT("Failed to start recording"));
}

// Stop recording — returns void
Service->StopRecording();

Method	Returns	Description
`StartRecording()`	`bool`	Starts recording. Returns true on success. Only valid when in Idle state.
`StopRecording()`	`void`	Stops the current recording. Only valid when in Recording or Paused state.

For async recording with callbacks and progress tracking, use ULCKRecorderSubsystem::StartRecordingAsync() and StopRecordingAsync() directly. See ULCKRecorderSubsystem for details.

PauseRecording / ResumeRecording

// Pause the current recording
Service->PauseRecording();

// Resume a paused recording
Service->ResumeRecording();

IsRecording / GetCurrentRecordingDuration

// Check if currently recording
bool bIsRecording = Service->IsRecording();

// Get recording duration in seconds
float Duration = Service->GetCurrentRecordingDuration();

// Update UI
if (bIsRecording)
{
    FTimespan Time = FTimespan::FromSeconds(Duration);
    TimerText->SetText(FText::Format(
        LOCTEXT("RecordingTime", "{0}:{1:02}"),
        Time.GetMinutes(),
        Time.GetSeconds()
    ));
}

GetRecordingState

ELCKRecordingState State = Service->GetRecordingState();

switch (State)
{
    case ELCKRecordingState::Idle:
        // Ready to record
        break;
    case ELCKRecordingState::Recording:
        // Currently recording
        break;
    // ...
}

Photo Capture

// Take a photo
Service->TakePhoto();

The photo is captured from the current scene capture component. There is no completion delegate on ULCKService for photo saves.

Recording Settings

ApplyRecordingSettings

Configure resolution, framerate, and bitrate for recordings:

Service->ApplyRecordingSettings(
    1920,   // Width
    1080,   // Height
    30,     // Framerate
    8 << 20, // Video bitrate (8 Mbps)
    256 << 10, // Audio bitrate (256 Kbps)
    48000   // Sample rate (optional, defaults to 48000)
);

Parameter	Type	Description
`Width`	`int32`	Video width in pixels
`Height`	`int32`	Video height in pixels
`Framerate`	`int32`	Frames per second
`VideoBitrate`	`int32`	Video bitrate in bits per second
`AudioBitrate`	`int32`	Audio bitrate in bits per second
`Samplerate`	`int32`	Audio sample rate (default: 48000)

Quality and orientation presets (SD, HD, Landscape, Portrait) are managed via ULCKTabletDataModel, not ULCKService. See the Data Model Events section below.

Audio Control

Microphone

// Enable/disable microphone
Service->SetMicrophoneEnabled(true);

// Get current state
bool bMicEnabled = Service->IsMicrophoneEnabled();

// Get microphone audio level (0.0 to 1.0)
float MicLevel = Service->GetCurrentMicrophoneAudioLevel();

Volume indicator example:

void AMicIndicator::Tick(float DeltaTime)
{
    Super::Tick(DeltaTime);

    float Volume = Service->GetCurrentMicrophoneAudioLevel();
    VolumeBar->SetPercent(Volume);

    // Visual feedback
    if (Volume > 0.7f)
    {
        VolumeBar->SetFillColorAndOpacity(FLinearColor::Red);
    }
    else if (Volume > 0.3f)
    {
        VolumeBar->SetFillColorAndOpacity(FLinearColor::Yellow);
    }
    else
    {
        VolumeBar->SetFillColorAndOpacity(FLinearColor::Green);
    }
}

GetCurrentMicrophoneAudioLevel() is not exposed to Blueprint. It is available from C++ only.

Preview Mode

Preview mode (camera output without recording to disk) is managed by ULCKRecorderSubsystem, not ULCKService.

// Access via the recorder subsystem directly
ULCKRecorderSubsystem* Recorder = GetWorld()->GetSubsystem<ULCKRecorderSubsystem>();
Recorder->StartPreview();
Recorder->StopPreview();

See ULCKRecorderSubsystem for details.

Delegates on ULCKService

ULCKService exposes the following delegates directly:

Delegate	Type	Description
`OnRecordingError`	`FOnRecordingError(FString ErrorMessage, int32 ErrorCode)`	Fired when a recording error occurs
`OnCameraModeChanged`	`FOnCameraModeChanged(UClass* ModeClass)`	Fired when the camera mode class changes
`OnRecordingSaveFinished`	`FOnRecordingSaveFinished(bool Success)`	Fired when the async save process completes
`OnRecordingSaveProgress`	`FOnRecordingSaveProgress(float Progress)`	Fired during save with progress from 0.0 to 1.0

Example: Subscribing to delegates

// Error handling
Service->OnRecordingError.AddDynamic(this, &UMyComponent::HandleRecordingError);

// Save completion
Service->OnRecordingSaveFinished.AddDynamic(this, &UMyComponent::HandleSaveFinished);

// Save progress
Service->OnRecordingSaveProgress.AddDynamic(this, &UMyComponent::HandleSaveProgress);

// Handlers
UFUNCTION()
void HandleRecordingError(FString ErrorMessage, int32 ErrorCode)
{
    UE_LOG(LogLCK, Error, TEXT("Recording error %d: %s"), ErrorCode, *ErrorMessage);
}

UFUNCTION()
void HandleSaveFinished(bool bSuccess)
{
    if (bSuccess)
    {
        ShowNotification(TEXT("Recording saved!"));
    }
}

UFUNCTION()
void HandleSaveProgress(float Progress)
{
    ProgressBar->SetPercent(Progress);
}

State Tracking via Data Model

For UI-level state notifications (recording state changes, quality changes, orientation changes, camera mode switches), use ULCKTabletDataModel.

Get the Data Model

void UMyComponent::BeginPlay()
{
    Super::BeginPlay();

    // Find tablet in world
    ALCKTablet* Tablet = Cast<ALCKTablet>(
        UGameplayStatics::GetActorOfClass(GetWorld(), ALCKTablet::StaticClass())
    );

    if (Tablet)
    {
        ULCKTabletDataModel* DataModel = Tablet->GetDataModel();

        // Subscribe to recording state changes
        DataModel->OnRecordStateChanged.AddUObject(
            this, &UMyComponent::HandleStateChanged
        );
    }
}

The recording state delegate is OnRecordStateChanged (type FOnRecordStateChange), not OnRecordingStateChanged. These are non-dynamic multicast delegates — use AddUObject or AddLambda, not AddDynamic.

Available Data Model Events

Event	Delegate Type	Parameter	Description
`OnRecordStateChanged`	`FOnRecordStateChange`	`ELCKRecordingState`	Recording state changed (Idle, Recording, etc.)
`OnTabletCameraModeChanged`	`FOnTabletCameraModeChanged`	`UClass*`	Camera mode class changed
`OnMicStateChanged`	`FOnMicStateChanged`	`ELCKMicState`	Microphone state changed (On, Off, No_Access)
`OnVideoQualityChanged`	`FOnVideoQualityChanged`	`ELCKVideoQuality`	Video quality preset changed
`OnScreenOrientationChanged`	`FOnScreenOrientationChanged`	`ELCKScreenOrientation`	Screen orientation changed
`OnMicLevelChanged`	`FOnMicLevelChanged`	`float`	Microphone audio level updated

Example: State-driven UI

void URecordingUI::HandleStateChanged(ELCKRecordingState NewState)
{
    switch (NewState)
    {
        case ELCKRecordingState::Idle:
            RecordButton->SetText(FText::FromString("Start Recording"));
            RecordButton->SetIsEnabled(true);
            ProgressPanel->SetVisibility(ESlateVisibility::Collapsed);
            break;

        case ELCKRecordingState::Recording:
            RecordButton->SetText(FText::FromString("Stop Recording"));
            RecordButton->SetIsEnabled(true);
            RecordingIndicator->SetVisibility(ESlateVisibility::Visible);
            break;

        case ELCKRecordingState::Saving:
            RecordButton->SetIsEnabled(false);
            ProgressPanel->SetVisibility(ESlateVisibility::Visible);
            StatusText->SetText(FText::FromString("Saving..."));
            break;

        case ELCKRecordingState::Error:
            RecordButton->SetIsEnabled(true);
            ShowErrorDialog();
            break;
    }
}

Streaming Methods

ULCKService also provides streaming functionality when the streaming feature is available:

Method	Returns	Description
`IsStreamingAvailable()`	`bool`	Whether the streaming feature plugin is loaded
`StartLogin()`	`void`	Begin the streaming login/pairing flow
`CancelLogin()`	`void`	Cancel an in-progress login
`Logout()`	`void`	Log out of the streaming service
`StartStreaming()`	`bool`	Start streaming; returns true on success
`StopStreaming()`	`void`	Stop the current stream
`IsStreaming()`	`bool`	Whether currently streaming
`IsAuthenticated()`	`bool`	Whether logged in to the streaming service
`LaunchHub()`	`void`	Launch the LIV Hub companion app
`IsHubInstalled()`	`bool`	Whether the LIV Hub app is installed
`GetLastLogoutReason()`	`FString`	Reason for the last logout
`GetStreamingTargetName()`	`FString`	Name of the current streaming target

Streaming Delegates

These are non-dynamic multicast delegates (use AddUObject or AddLambda):

Delegate	Type	Description
`OnStreamingPairingCode`	`FOnStreamingPairingCode(const FString&)`	Pairing code received during login
`OnStreamingAuthenticated`	`FOnStreamingAuthenticated()`	Successfully authenticated
`OnStreamingStarted`	`FOnStreamingStarted()`	Streaming session started
`OnStreamingStopped`	`FOnStreamingStopped()`	Streaming session stopped
`OnStreamingError`	`FOnStreamingError(const FString&)`	Streaming error occurred
`OnStreamingLoggedOut`	`FOnStreamingLoggedOut()`	Logged out of streaming service
`OnStreamingConfigChanged`	`FOnStreamingConfigChanged()`	Streaming configuration changed

Complete Example: Recording Manager

UCLASS()
class URecordingManager : public UActorComponent
{
    GENERATED_BODY()

protected:
    UPROPERTY()
    ULCKService* Service;

    UPROPERTY()
    ULCKTabletDataModel* DataModel;

public:
    virtual void BeginPlay() override
    {
        Super::BeginPlay();

        // Get service
        Service = GetLCKService();
        if (!Service)
        {
            UE_LOG(LogLCK, Error, TEXT("LCK Service not available"));
            return;
        }

        // Get data model for state tracking
        ALCKTablet* Tablet = FindTablet();
        if (Tablet)
        {
            DataModel = Tablet->GetDataModel();
            DataModel->OnRecordStateChanged.AddUObject(
                this, &URecordingManager::OnStateChanged
            );
        }

        // Subscribe to service events
        Service->OnRecordingSaveFinished.AddDynamic(
            this, &URecordingManager::OnSaveFinished
        );
        Service->OnRecordingError.AddDynamic(
            this, &URecordingManager::OnError
        );
    }

    UFUNCTION(BlueprintCallable)
    void ToggleRecording()
    {
        if (Service->IsRecording())
        {
            Service->StopRecording();
        }
        else
        {
            bool bSuccess = Service->StartRecording();
            if (!bSuccess)
            {
                UE_LOG(LogLCK, Error, TEXT("Failed to start recording"));
            }
        }
    }

    void OnStateChanged(ELCKRecordingState NewState)
    {
        // Update UI based on state
        BroadcastStateChange(NewState);
    }

    UFUNCTION()
    void OnSaveFinished(bool bSuccess)
    {
        if (bSuccess)
        {
            ShowNotification(TEXT("Recording saved!"));
        }
        else
        {
            ShowError(TEXT("Failed to save recording"));
        }
    }

    UFUNCTION()
    void OnError(FString ErrorMessage, int32 ErrorCode)
    {
        UE_LOG(LogLCK, Error, TEXT("Recording error %d: %s"), ErrorCode, *ErrorMessage);
        ShowErrorDialog(ErrorMessage);
    }

private:
    ULCKService* GetLCKService()
    {
        if (UWorld* World = GetWorld())
        {
            if (ULCKSubsystem* Subsystem = World->GetSubsystem<ULCKSubsystem>())
            {
                return Subsystem->GetService();
            }
        }
        return nullptr;
    }

    ALCKTablet* FindTablet()
    {
        return Cast<ALCKTablet>(
            UGameplayStatics::GetActorOfClass(GetWorld(), ALCKTablet::StaticClass())
        );
    }
};

Key Takeaways

Get via ULCKSubsystem — Don’t create or cache manually

Check IsRecording() — Before changing settings or starting

Use DataModel for state events — Subscribe to OnRecordStateChanged on ULCKTabletDataModel

Preview lives on ULCKRecorderSubsystem — Not on ULCKService

Quality and orientation are on DataModel — Use ULCKTabletDataModel to change presets

Delegates Reference — All event delegates
Error Codes — Error handling
Enums Reference — All enum values
Architecture — How ULCKService fits into the system

​What Problem Does This Solve?

​When to Use This

​Accessing the Service

​From C++

​From Blueprint

​Recording Methods

​StartRecording / StopRecording

​PauseRecording / ResumeRecording

​IsRecording / GetCurrentRecordingDuration

​GetRecordingState

​Photo Capture

​Recording Settings

​ApplyRecordingSettings

​Audio Control

​Microphone

​Preview Mode

​Delegates on ULCKService

​State Tracking via Data Model

​Get the Data Model

​Available Data Model Events

​Streaming Methods

​Streaming Delegates

​Complete Example: Recording Manager

​Key Takeaways

​Related

What Problem Does This Solve?

When to Use This

Accessing the Service

From C++

From Blueprint

Recording Methods

StartRecording / StopRecording

PauseRecording / ResumeRecording

IsRecording / GetCurrentRecordingDuration

GetRecordingState

Photo Capture

Recording Settings

ApplyRecordingSettings

Audio Control

Microphone

Preview Mode

Delegates on ULCKService

State Tracking via Data Model

Get the Data Model

Available Data Model Events

Streaming Methods

Streaming Delegates

Complete Example: Recording Manager

Key Takeaways

Related