Recording - LCK Documentation

ULCKRecorderSubsystem

The recorder subsystem manages the complete recording lifecycle as a UTickableWorldSubsystem. It handles scene capture, encoder coordination, and audio mixing each tick.

Class Definition

UCLASS()
class LCKCORE_API ULCKRecorderSubsystem : public UTickableWorldSubsystem
{
    GENERATED_BODY()

public:
    // Scene capture component for video source
    UPROPERTY(Category = "LCK", BlueprintReadOnly)
    USceneCaptureComponent2D* CaptureComponent;

    // Render target for capture
    UPROPERTY(Category = "LCK", BlueprintReadOnly)
    UTextureRenderTarget2D* RenderTarget;
};

Setup Methods

SetupRecorder

function

Initializes the recorder with parameters and optional capture component.

UFUNCTION(Category="LCK", BlueprintCallable)
void SetupRecorder(
    const FLCKRecorderParams& RecorderParams,
    USceneCaptureComponent2D* InitialCaptureComponent = nullptr
);

SetSceneCaptureComponent

function

Sets or changes the scene capture component used for video source.

UFUNCTION(Category="LCK", BlueprintCallable)
void SetSceneCaptureComponent(USceneCaptureComponent2D* NewSceneCaptureComponent);

Recording Control

StartRecording

function

Begins recording. Returns false if already recording or encoder unavailable.

UFUNCTION(Category="LCK", BlueprintCallable)
bool StartRecording();

StopRecording

function

Stops recording and finalizes the video file.

UFUNCTION(Category="LCK", BlueprintCallable)
bool StopRecording();

TakePhoto

function

Captures a single frame as a photo.

UFUNCTION(Category="LCK", BlueprintCallable)
bool TakePhoto();

Async Methods

For non-blocking operations with callbacks:

// Start recording with callback
void StartRecordingAsync(FOnLCKRecorderBoolResult OnResult);

// Stop recording with progress callback
void StopRecordingAsync(
    FOnLCKRecorderBoolResult OnResult,
    FOnLCKRecorderProgress OnProgress
);

Recorder->StartRecordingAsync(
    FOnLCKRecorderBoolResult::CreateLambda([](bool bSuccess) {
        if (bSuccess)
            UE_LOG(LogTemp, Log, TEXT("Recording started"));
        else
            UE_LOG(LogTemp, Error, TEXT("Failed to start recording"));
    })
);

Recorder->StopRecordingAsync(
    FOnLCKRecorderBoolResult::CreateLambda([](bool bSuccess) {
        UE_LOG(LogTemp, Log, TEXT("Recording stopped: %s"),
            bSuccess ? TEXT("Success") : TEXT("Failed"));
    }),
    FOnLCKRecorderProgress::CreateLambda([](float Progress) {
        UE_LOG(LogTemp, Log, TEXT("Save progress: %.1f%%"), Progress * 100.0f);
    })
);

State Queries

IsRecording

function

Returns true if currently recording.

UFUNCTION(BlueprintCallable, Category = "LCK")
bool IsRecording() const;

GetTime

function

Returns current recording duration in seconds.

UFUNCTION(BlueprintCallable, Category = "LCK")
float GetTime() const;

GetMicrophoneVolume

function

Returns current microphone input level (0.0 - 1.0).

UFUNCTION(BlueprintCallable, Category = "LCK")
float GetMicrophoneVolume() const;

Microphone Control

SetMicrophoneEnabled

function

Enables or disables microphone audio in recordings.

UFUNCTION(BlueprintCallable, Category = "LCK")
void SetMicrophoneEnabled(bool bEnabled);

IsMicrophoneEnabled

function

Returns whether microphone audio is enabled.

UFUNCTION(BlueprintPure, Category = "LCK")
bool IsMicrophoneEnabled() const;

FLCKRecorderParams

Recording configuration structure.

USTRUCT(BlueprintType)
struct LCKCORE_API FLCKRecorderParams
{
    GENERATED_BODY()

    UPROPERTY(Category="LCK", EditAnywhere, BlueprintReadWrite)
    int32 Width = 1920;

    UPROPERTY(Category="LCK", EditAnywhere, BlueprintReadWrite)
    int32 Height = 1080;

    UPROPERTY(Category="LCK", EditAnywhere, BlueprintReadWrite)
    int32 Framerate = 30;

    UPROPERTY(Category="LCK", EditAnywhere, BlueprintReadWrite)
    int32 VideoBitrate = 2 << 20;  // 2 Mbps default

    UPROPERTY(Category="LCK", EditAnywhere, BlueprintReadWrite)
    int32 Samplerate = 48000;

    UPROPERTY(Category="LCK", EditAnywhere, BlueprintReadWrite)
    int32 AudioBitrate = 256 << 10;  // 256 Kbps default
};

Recommended Settings

Quality	Resolution	FPS	Video Bitrate	Audio Bitrate
SD	1280 x 720	30	4 Mbps	128 Kbps
HD	1920 x 1080	60	12 Mbps	256 Kbps
2K	2560 x 1440	60	20 Mbps	320 Kbps
4K	3840 x 2160	60	35 Mbps	320 Kbps

Higher resolutions significantly impact performance, especially on mobile VR devices. Test thoroughly on target hardware.

Delegates

FOnLCKRecorderBoolResult

Result callback for async operations.

DECLARE_DELEGATE_OneParam(FOnLCKRecorderBoolResult, bool /*bSuccess*/);

FOnLCKRecorderProgress

Progress callback for save operations.

DECLARE_DELEGATE_OneParam(FOnLCKRecorderProgress, float /*Progress*/);

Preview Mode

For live camera preview without recording:

// Start preview (capture frames but don't encode)
Recorder->StartPreview();

// Stop preview
Recorder->StopPreview();

Preview mode is useful for camera composition and settings adjustment before recording.

​ULCKRecorderSubsystem

​Class Definition

​Setup Methods

​Recording Control

​Async Methods

​State Queries

​Microphone Control

​FLCKRecorderParams

​Recommended Settings

​Delegates

​FOnLCKRecorderBoolResult

​FOnLCKRecorderProgress

​Preview Mode

ULCKRecorderSubsystem

Class Definition

Setup Methods

Recording Control

Async Methods

State Queries

Microphone Control

FLCKRecorderParams

Recommended Settings

Delegates

FOnLCKRecorderBoolResult

FOnLCKRecorderProgress

Preview Mode