Unreal音频录制流程分析

Posted 2023-04-01 碧麟

先看一下录音数据的存储结构

	/************************************************************************/
	/* FAudioRecordingData                                                  */
	/* This is used by USoundSubmix and the AudioMixerBlueprintLibrary      */
	/* to contain FSoundWavePCMWriter operations.                           */
	/************************************************************************/
	struct FAudioRecordingData
	
		TSampleBuffer<int16> InputBuffer;
		FSoundWavePCMWriter Writer;

		~FAudioRecordingData() ;
	;

其中，TSampleBuffer结构如下

template <class SampleType = DefaultUSoundWaveSampleType>
	class TSampleBuffer
	
	private:
		// raw PCM data buffer
		TArray<SampleType> RawPCMData;
		// The number of samples in the buffer
		int32 NumSamples;
		// The number of frames in the buffer
		int32 NumFrames;
		// The number of channels in the buffer
		int32 NumChannels;
		// The sample rate of the buffer	
		int32 SampleRate;
		// The duration of the buffer in seconds
		float SampleDuration;
    

录制音频的关键函数

USoundWave* UAudioMixerBlueprintLibrary::StopRecordingOutput(const UObject* WorldContextObject, EAudioRecordingExportType ExportType, const FString& Name, FString Path, USoundSubmix* SubmixToRecord, USoundWave* ExistingSoundWaveToOverwrite)

	if (RecordingData.IsValid())
	
		UE_LOG(LogAudioMixer, Warning, TEXT("Abandoning existing write operation. If you\'d like to export multiple submix recordings at the same time, use Start/Finish Recording Submix Output instead."));
	

	if (Audio::FMixerDevice* MixerDevice = FAudioDeviceManager::GetAudioMixerDeviceFromWorldContext(WorldContextObject))
	
		float SampleRate;
		float ChannelCount;

		// call the thing here.
		Audio::FAlignedFloatBuffer& RecordedBuffer = MixerDevice->StopRecording(SubmixToRecord, ChannelCount, SampleRate);

		if (RecordedBuffer.Num() == 0)
		
			UE_LOG(LogAudioMixer, Warning, TEXT("No audio data. Did you call Start Recording Output?"));
			return nullptr;
		

		// Pack output data into a TSampleBuffer and record out:
		RecordingData.Reset(new Audio::FAudioRecordingData());
		RecordingData->InputBuffer = Audio::TSampleBuffer<int16>(RecordedBuffer, ChannelCount, SampleRate);

		switch (ExportType)
		
		case EAudioRecordingExportType::SoundWave:
		
			USoundWave* ResultingSoundWave = RecordingData->Writer.SynchronouslyWriteSoundWave(RecordingData->InputBuffer, &Name, &Path);
			RecordingData.Reset();
			return ResultingSoundWave;
			break;
		
		case EAudioRecordingExportType::WavFile:
		
			RecordingData->Writer.BeginWriteToWavFile(RecordingData->InputBuffer, Name, Path, [SubmixToRecord]()
			
				if (SubmixToRecord && SubmixToRecord->OnSubmixRecordedFileDone.IsBound())
				
					SubmixToRecord->OnSubmixRecordedFileDone.Broadcast(nullptr);
				

				// I\'m gonna try this, but I do not feel great about it.
				RecordingData.Reset();
			);
			break;
		
		default:
			break;
			
	
	else
	
		UE_LOG(LogAudioMixer, Error, TEXT("Output recording is an audio mixer only feature."));
	

	return nullptr;

 

认真写好每一行代码

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