How to change sound volume in C++?

Development Audio
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1

How to change a sound class’s volume in C++? I’m trying to build an audio options menu, where you can configure the Master (overall) volume, Effects volume, Music volume, Voice volume, etc.

I tried changing it via GEngine->GetAudioDevice()->SetClassVolume(SoundClass, Volume);, but nothing happens. Below is the full code.

void FShooterOptions::ChangeVolume(FString ClassName, float Volume)
{
	FAudioDevice* Device = GEngine->GetAudioDevice();
	if (!Device)
	{
		return;
	}
	
	USoundClass* SoundClass = NULL;
	for (TMap<USoundClass*, FSoundClassProperties>::TIterator It(Device->SoundClasses); It; ++It)
	{
		USoundClass* ThisSoundClass = It.Key();
		if (ThisSoundClass && ThisSoundClass->GetFullName().Find(ClassName) != INDEX_NONE)
		{
			SoundClass = ThisSoundClass;
			break;
		}
	}

	if (SoundClass)
	{
		Device->SetClassVolume(SoundClass, Volume);
	}
}

I debugged the code and it was finding the sound classes (Master, SFX, etc.), and it was assigning the new values, but the volume didn’t actually change.

2

I’ve managed to achieve that by changing sound class volume property. Instead of

Device->SetClassVolume(SoundClass, Volume);

try

SoundClass->Properties.Volume = NewMasterSoundVolume;

Also make sure there is only one “Master” sound class.

3

Also make sure there is only one “Master” sound class.

That was the problem! There were 3 ‘Master’ sound classes registered on the device, for some reason. Hmm ahh: one from the Engine, one from Game/Sounds (maybe from ShooterGame), and one from Game/ExampleContent (from the examples project).

So the solution is:

void FShooterOptions::ChangeVolume(FString ClassName, float Volume)
{
	FAudioDevice* Device = GEngine->GetAudioDevice();
	if (!Device)
	{
		return;
	}
	
	for (TMap<USoundClass*, FSoundClassProperties>::TIterator It(Device->SoundClasses); It; ++It)
	{
		USoundClass* SoundClass = It.Key();
		if (SoundClass && SoundClass->GetFullName().Find(ClassName) != INDEX_NONE)
		{
			Device->SetClassVolume(SoundClass, Volume);
		}
	}
}

Thanks!

4

Thanks for posting this code - was a great time saver!

5

Since 4.7 it’s

SoundClass->Properties.Volume = Volume;

instead of

Device->SetClassVolume(SoundClass, Volume);
6

Small improvement

I’d like to suggest a small improvement I did on the function. As the finding class by name part uses FString::Find it could get the wrong class searching for a name that’s part of another class. For example, it could give you SFX_Weapons while searching for SFX, as SFX_Weapons also contains SFX. So, instead, I look for the part after the . in the full name. The names are like *Engine/Something/Sound.Master * , so the class name we look for is right after the only . in the name. Splitting the name by the . and getting the right part, we have the class name only.

Code (tested on 4.10.4)

#include "AudioDevice.h"

void SetSoundClassVolume(FString ClassName, float Volume, bool &Success)
{
	FAudioDevice* AudioDevice = GEngine->GetMainAudioDevice();

	Success = false;
	if (!AudioDevice) return;

	for (auto i = AudioDevice->SoundClasses.CreateIterator(); i; ++i)
	{
		USoundClass* SoundClass = i.Key();
		FString SoundClassName;

		// Test if the Split function works then, if the name was the right one
		if (SoundClass->GetFullName().Split(L".", nullptr, &SoundClassName, ESearchCase::CaseSensitive)
			&& SoundClassName.Equals(ClassName))
		{
			SoundClass->Properties.Volume = Volume;
			Success = true;
			return;
		}
	}
}
7

In the newer version of Unreal Engine FAudioDevice::SoundClasses has been made private. Instead the default USoundClass can be easily accessed from UAudioSettings or if the access of a custom USoundClass is desired it can be accessed by calling LoadObject<>().

// Change volume of SoundClass by specifying asset path to SoundClass
ChangeVolume(float volume, FSoftObjectPath soundClassPath) {

    // Guard statement against invalid FSoftObjectPath
	if (!soundClassPath.IsValid())
	{
		return;
	}

    // Load object if not already loaded
	USoundClass* soundClass = LoadObject<USoundClass>(nullptr, *soundClassPath.ToString());

    // Guard against unsuccessful object instantiation
	if (soundClass == nullptr) {
		return;
	}

    // 
	soundClass->Properties.Volume = volume;
}

// Change the volume of the default SoundClass
ChangeDefaultVolume(float volume) {
     const FSoftObjectPath DefaultSoundClassName = GetDefault<UAudioSettings>()->DefaultSoundClassName;
	
	if (!DefaultSoundClassName.IsValid())
	{
		return;
	}

	USoundClass* masterSoundClass = LoadObject<USoundClass>(nullptr, *DefaultSoundClassName.ToString());

	if (masterSoundClass == nullptr) {
		return;
	}

	masterSoundClass->Properties.Volume = volume;
}
1 Like
8

@Dantali0n Do you have any idea how to set the volume of a media player?