Playing sound wave from code

Development Programming & Scripting
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1

I’m trying to download a song, and then to play it once the download is finished. I don’t want to download the song on my hard drive, but rather to keep it in memory, that’s why when I made TMap<FString, UAudioComponent*> EventAudios in my AMyActor class as a private variable. I got this code:

void AMyActor::DownloadSong(const FString& URL, const FString& eventId)
{
	TSharedRef<IHttpRequest> HttpRequest = FHttpModule::Get().CreateRequest();
	HttpRequest->SetVerb(TEXT("GET"));
	HttpRequest->SetURL(URL);

	HttpRequest->OnProcessRequestComplete().BindLambda([=](FHttpRequestPtr Request, FHttpResponsePtr Response, bool bWasSuccessful) {
		OnDownloadComplete(Request, Response, bWasSuccessful, eventId);
		});

	HttpRequest->ProcessRequest();
}

void AMyActor::OnDownloadComplete(FHttpRequestPtr Request, FHttpResponsePtr Response, bool bSuccess, const FString& eventId)
{
	if (bSuccess && Response->GetContentLength() > 0)
	{
		TArray<uint8> DownloadedData = Response->GetContent();

		// Create a sound wave object
		USoundWave* SoundWave = NewObject<USoundWave>(USoundWave::StaticClass());

		// Set the sound wave properties
		SoundWave->SoundGroup = ESoundGroup::SOUNDGROUP_Default;
		SoundWave->NumChannels = 2; // Assuming 2 channels for AAC audio
		SoundWave->Duration = 0.0f; // Set the duration to 0 to indicate it is streaming

		// Clear the raw audio data of the sound wave
		SoundWave->RawData.RemoveBulkData();

		// Set the raw audio data of the sound wave
		int32 NumSamples = DownloadedData.Num() / (sizeof(int16) * SoundWave->NumChannels);
		SoundWave->RawData.Lock(LOCK_READ_WRITE);
		int16* RawDataPtr = (int16*)SoundWave->RawData.Realloc(DownloadedData.Num());
		FMemory::Memcpy(RawDataPtr, DownloadedData.GetData(), DownloadedData.Num());
		SoundWave->RawData.Unlock();

		// Set the sample rate
		SoundWave->SetSampleRate(44100); // Set the appropriate sample rate for your audio

		// Create an audio component and set its properties
		UAudioComponent* AudioComponent = UGameplayStatics::CreateSound2D(this, SoundWave);
		AudioComponent->SetVolumeMultiplier(1.0f);
		AudioComponent->SetPitchMultiplier(1.0f);
		AudioComponent->bAutoDestroy = true;

		// Add audio to the map of events
		if (EventAudios.Find(eventId))
		{
			EventAudios[eventId] = AudioComponent;
		}
		else
		{
			EventAudios.Emplace(eventId, AudioComponent);
		}

		// Play the audio
		EventAudios[eventId]->Play();
	}

However it does not play a sound when I call DownloadSong. What am I doing wrong?
PS: I am using Unreal Engine 4.25, and I’m trying to play AAC file format.

2

Hi. You can take a look at RuntimeAudioImporter, specifically ImportedSoundWave, where it uses a procedural sound wave and plays back a custom buffer in the OnGeneratePCMAudio method. The engine has multiple audio buffers such as RawPCMData, RawData, CookedPlatformData, and a streaming one, but they are not reliable and exhibit different behaviors in different engine versions. Personally, I recommend implementing this logic on top of the procedural sound wave instead, or using the mentioned plugin where it’s already implemented.