video-record-ue-poc/Source/AudioVideoRecord/SimpleRecorder.h

// SimpleRecorder.h — In-game gameplay recorder (Video + Audio + Mux)
// Captures the Unreal back buffer & audio submix, pipes to FFmpeg/NVENC.

#pragma once

#include "CoreMinimal.h"
#include "UObject/Object.h"
#include "Sound/SoundSubmix.h"
#include "ISubmixBufferListener.h"
#include "SimpleRecorder.generated.h"


// ─────────────────────────────────────────────────────────────────────
// USimpleRecorder
//
// A UObject-based recorder you can create from Blueprint or C++.
//   • StartRecording()  — begins video + audio capture
//   • StopRecording()   — stops capture, writes .wav, muxes final .mp4
//
// Outputs (inside <ProjectDir>/Saved/Recordings/):
//   video_only.mp4          — NVENC-encoded H.264
//   audio_only.wav          — PCM 16-bit
//   final_video_with_audio.mp4 — muxed result
// ─────────────────────────────────────────────────────────────────────
UCLASS(BlueprintType)
class AUDIOVIDEORECORD_API USimpleRecorder : public UObject
{
	GENERATED_BODY()

public:
	USimpleRecorder();

	// ── Blueprint-callable API ───────────────────────────────────────
	/** Starts capturing video frames and audio. */
	UFUNCTION(BlueprintCallable, Category = "SimpleRecorder")
	void StartRecording();

	/** Stops capturing. Saves audio_only.wav, then muxes the final file. */
	UFUNCTION(BlueprintCallable, Category = "SimpleRecorder")
	void StopRecording();

	/** Returns true while recording is active. */
	UFUNCTION(BlueprintCallable, BlueprintPure, Category = "SimpleRecorder")
	bool IsRecording() const { return bIsRecording; }

	// ── Configurable settings (edit before calling StartRecording) ───
	/** If true, capture resolution is auto-detected from the viewport at recording start. */
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "SimpleRecorder|Settings")
	bool bAutoDetectResolution = true;

	/** Capture width in pixels (ignored if bAutoDetectResolution is true). */
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "SimpleRecorder|Settings")
	int32 CaptureWidth = 1920;

	/** Capture height in pixels (ignored if bAutoDetectResolution is true). */
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "SimpleRecorder|Settings")
	int32 CaptureHeight = 1080;

	/** Target frames per second. */
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "SimpleRecorder|Settings")
	int32 CaptureFPS = 60;

	/** Video bitrate string for FFmpeg (e.g. "8M", "12M"). */
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "SimpleRecorder|Settings")
	FString VideoBitrate = TEXT("8M");

	/** Directory where output files are saved (absolute or project-relative). */
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "SimpleRecorder|Settings")
	FString OutputDirectory;

	/** Full path to ffmpeg.exe. If empty we look on the system PATH. */
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "SimpleRecorder|Settings")
	FString FFmpegPath;

	/** The audio submix to record. If null, the engine master submix is used. */
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "SimpleRecorder|Settings")
	USoundSubmix* TargetSubmix = nullptr;

	// ── Audio submix callback (forwarded from bridge) ──────────────
	void OnNewSubmixBuffer(
		const USoundSubmix* OwningSubmix,
		float* AudioData,
		int32 NumSamples,
		int32 NumChannels,
		const int32 SampleRate,
		double AudioClock);

protected:
	virtual void BeginDestroy() override;

private:
	// ── Internal helpers ─────────────────────────────────────────────
	void InitOutputPaths();
	FString GetFFmpegExecutable() const;

	/** Called every frame on the render thread when the back buffer is ready. */
	void OnBackBufferReady(SWindow& SlateWindow, const FTextureRHIRef& BackBuffer);

	/** Writes the captured audio buffer to a .wav file. */
	void SaveAudioToWav();

	/** Runs FFmpeg to mux video_only.mp4 + audio_only.wav → final .mp4. */
	void MuxAudioVideo();

	// ── State ────────────────────────────────────────────────────────
	bool                       bIsRecording = false;

	// Video
	FDelegateHandle            BackBufferDelegateHandle;
	FILE*                      FFmpegVideoPipe = nullptr;

	// Audio — accumulated raw PCM data
	TArray<float>              AudioBuffer;          // interleaved float samples
	int32                      AudioSampleRate = 48000;
	int32                      AudioNumChannels = 2;
	FCriticalSection           AudioBufferCritSection;

	// Output file paths (computed once per recording session)
	FString                    VideoFilePath;
	FString                    AudioFilePath;
	FString                    FinalFilePath;

	// Submix bridge (UObjects can't be TSharedRef, so we use a bridge)
	TSharedPtr<ISubmixBufferListener, ESPMode::ThreadSafe> SubmixBridge;
};