LowFrequency

LowFrequency

#Overview

name: LowFrequency

The value of this variable can be defined or overridden in .ini config files. 1 .ini config file referencing this setting variable.

It is referenced in 43 C++ source files.

#Summary

#Usage in the C++ source code

The purpose of LowFrequency is to represent the Low-Frequency Effects (LFE) channel in audio systems, particularly in surround sound configurations. This channel is dedicated to handling low-frequency sounds, typically below 120 Hz, which are often used for bass effects in movies, games, and other multimedia content.

LowFrequency is primarily used in the audio rendering and mixing subsystems of Unreal Engine 5. It is referenced in various audio-related modules, including:

  1. AudioMixer
  2. SignalProcessing
  3. SoundFieldRendering
  4. AudioMixerXAudio2 (Windows-specific)
  5. Synthesis plugin

The value of this variable is typically set as part of channel configurations in audio systems. It’s often included in channel mapping arrays or enumerations that define the layout of multi-channel audio setups.

LowFrequency interacts with other audio channel variables such as FrontLeft, FrontRight, FrontCenter, BackLeft, BackRight, SideLeft, and SideRight. These variables collectively represent the different speakers in surround sound setups.

Developers should be aware of the following when using this variable:

  1. LowFrequency is often treated differently from other channels in audio processing. For example, it’s sometimes skipped in certain operations or given special treatment in audio encoding/decoding processes.
  2. Not all audio setups include an LFE channel, so code should be prepared to handle configurations with and without it.
  3. The LowFrequency channel is typically not used for directional audio cues due to its non-directional nature.

Best practices when using this variable include:

  1. Always check if the LowFrequency channel is present in the current audio configuration before attempting to use it.
  2. When implementing audio spatialization or 3D audio effects, consider excluding the LowFrequency channel as it’s typically non-directional.
  3. Be mindful of the LowFrequency channel’s unique properties when implementing audio mixing, effects, or processing algorithms.
  4. Ensure proper handling of the LowFrequency channel in different surround sound configurations (5.1, 7.1, etc.) to maintain consistent audio quality across various setups.

#Setting Variables

#References In INI files

Location: <Workspace>/Engine/Config/BaseEngine.ini:1588, section: [AudioDefaultChannelOrder]

#References in C++ code

#Callsites

This variable is referenced in the following C++ source code:

#Loc: <Workspace>/Engine/Plugins/Runtime/Synthesis/Source/Synthesis/Private/ConvolutionReverb.cpp:49

Scope (from outer to inner):

file
namespace    Audio
namespace    ConvolutionReverbIntrinsics

Source code excerpt:

				EAudioMixerChannel::Type::FrontRight,
				EAudioMixerChannel::Type::FrontCenter,
				EAudioMixerChannel::Type::LowFrequency,
				EAudioMixerChannel::Type::SideLeft,
				EAudioMixerChannel::Type::SideRight
			},

			// Seven channels (7.0)
			{

#Loc: <Workspace>/Engine/Plugins/Runtime/Synthesis/Source/Synthesis/Private/ConvolutionReverb.cpp:70

Scope (from outer to inner):

file
namespace    Audio
namespace    ConvolutionReverbIntrinsics

Source code excerpt:

				EAudioMixerChannel::Type::FrontRight,
				EAudioMixerChannel::Type::FrontCenter,
				EAudioMixerChannel::Type::LowFrequency,
				EAudioMixerChannel::Type::BackLeft,
				EAudioMixerChannel::Type::BackRight,
				EAudioMixerChannel::Type::SideLeft,
				EAudioMixerChannel::Type::SideRight
			}
		};

#Loc: <Workspace>/Engine/Plugins/Runtime/Synthesis/Source/Synthesis/Private/SubmixChannelFormatConverter.cpp:94

Scope (from outer to inner):

file
namespace    Audio
function     bool GetSubmixChannelOrderForNumChannels

Source code excerpt:

						EAudioMixerChannel::Type::FrontRight,
						EAudioMixerChannel::Type::FrontCenter,
						EAudioMixerChannel::Type::LowFrequency,
						EAudioMixerChannel::Type::SideLeft,
						EAudioMixerChannel::Type::SideRight
					}
				);

				return true;

#Loc: <Workspace>/Engine/Plugins/Runtime/Synthesis/Source/Synthesis/Private/SubmixChannelFormatConverter.cpp:110

Scope (from outer to inner):

file
namespace    Audio
function     bool GetSubmixChannelOrderForNumChannels

Source code excerpt:

						EAudioMixerChannel::Type::FrontRight,
						EAudioMixerChannel::Type::FrontCenter,
						EAudioMixerChannel::Type::LowFrequency,
						EAudioMixerChannel::Type::BackLeft,
						EAudioMixerChannel::Type::BackRight,
						EAudioMixerChannel::Type::SideLeft,
						EAudioMixerChannel::Type::SideRight
					}
				);

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixer/Private/AudioMixerChannelMaps.cpp:35

Scope (from outer to inner):

file
namespace    Audio

Source code excerpt:

			EAudioMixerChannel::FrontRight,
			EAudioMixerChannel::FrontCenter,
			EAudioMixerChannel::LowFrequency,
			EAudioMixerChannel::SideLeft,
			EAudioMixerChannel::SideRight
		},

		// ESubmixChannelFormat::SevenDotOne
		{

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixer/Private/AudioMixerChannelMaps.cpp:45

Scope (from outer to inner):

file
namespace    Audio

Source code excerpt:

			EAudioMixerChannel::FrontRight,
			EAudioMixerChannel::FrontCenter,
			EAudioMixerChannel::LowFrequency,
			EAudioMixerChannel::BackLeft,
			EAudioMixerChannel::BackRight,
			EAudioMixerChannel::SideLeft,
			EAudioMixerChannel::SideRight
		},

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixer/Private/AudioMixerChannelMaps.cpp:60

Scope (from outer to inner):

file
namespace    Audio

Source code excerpt:

			EAudioMixerChannel::FrontRight,
			EAudioMixerChannel::FrontCenter,
			EAudioMixerChannel::LowFrequency,
			EAudioMixerChannel::BackLeft,
			EAudioMixerChannel::BackRight,
			EAudioMixerChannel::SideLeft,
			EAudioMixerChannel::SideRight
		}, 
	};

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixer/Private/AudioMixerChannelMaps.cpp:233

Scope (from outer to inner):

file
namespace    Audio
function     void FMixerDevice::InitializeChannelAzimuthMap

Source code excerpt:


		// Always ignore low frequency channel for azimuth computations. 
		DefaultChannelAzimuthPositions[EAudioMixerChannel::LowFrequency] = { EAudioMixerChannel::LowFrequency, INDEX_NONE };

		DefaultChannelAzimuthPositions[EAudioMixerChannel::BackLeft] = { EAudioMixerChannel::BackLeft, 210 };
		DefaultChannelAzimuthPositions[EAudioMixerChannel::BackRight] = { EAudioMixerChannel::BackRight, 150 };
		DefaultChannelAzimuthPositions[EAudioMixerChannel::FrontLeftOfCenter] = { EAudioMixerChannel::FrontLeftOfCenter, 15 };
		DefaultChannelAzimuthPositions[EAudioMixerChannel::FrontRightOfCenter] = { EAudioMixerChannel::FrontRightOfCenter, 345 };
		DefaultChannelAzimuthPositions[EAudioMixerChannel::BackCenter] = { EAudioMixerChannel::BackCenter, 180 };

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixer/Private/AudioMixerChannelMaps.cpp:309

Scope (from outer to inner):

file
namespace    Audio
function     void FMixerDevice::InitializeChannelAzimuthMap

Source code excerpt:

		{
			// Only track non-LFE and non-Center channel azimuths for use with 3d channel mappings
			if (Channel != EAudioMixerChannel::LowFrequency && DefaultChannelAzimuthPositions[Channel].Azimuth >= 0)
			{
				DeviceChannelAzimuthPositions.Add(DefaultChannelAzimuthPositions[Channel]);
			}
		}
		DeviceChannelAzimuthPositions.Sort(FCompareByAzimuth());
	}

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixer/Private/AudioMixerDevice.cpp:444

Scope (from outer to inner):

file
namespace    Audio
function     TArray<Audio::FChannelPositionInfo>* FMixerDevice::GetDefaultPositionMap

Source code excerpt:

														,SpeakerPositions[EAudioMixerChannel::FrontRight] // right
														,SpeakerPositions[EAudioMixerChannel::FrontCenter] //center
														,SpeakerPositions[EAudioMixerChannel::LowFrequency] //LFE
														,SpeakerPositions[EAudioMixerChannel::SideLeft] //Left Rear
														,SpeakerPositions[EAudioMixerChannel::SideRight] //Right Rear
				};
				return &FiveDotOneMap;
			}

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixer/Private/AudioMixerDevice.cpp:458

Scope (from outer to inner):

file
namespace    Audio
function     TArray<Audio::FChannelPositionInfo>* FMixerDevice::GetDefaultPositionMap

Source code excerpt:

														,SpeakerPositions[EAudioMixerChannel::FrontRight] // right
														,SpeakerPositions[EAudioMixerChannel::FrontCenter] //center
														,SpeakerPositions[EAudioMixerChannel::LowFrequency] //LFE
														,SpeakerPositions[EAudioMixerChannel::BackLeft] // Left Rear
														,SpeakerPositions[EAudioMixerChannel::BackRight] // Right Rear
														,SpeakerPositions[EAudioMixerChannel::SideLeft] // Left Surround
														,SpeakerPositions[EAudioMixerChannel::SideRight] // Right Surround
				};

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixer/Private/AudioMixerDevice.cpp:2223

Scope (from outer to inner):

file
namespace    Audio
function     void FMixerDevice::Get3DChannelMap

Source code excerpt:


				// Check for manual channel mapping parameters (LFE and Front Center)
				if (Channel == EAudioMixerChannel::LowFrequency)
				{
					EffectivePan = InWaveInstance->LFEBleed;
				}
				else if (Channel == PrevChannelInfo->Channel)
				{
					EffectivePan = FMath::Lerp(PrevChannelPan, OmniPanFactor, OmniAmount);

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixer/Private/AudioMixerDevice.cpp:2256

Scope (from outer to inner):

file
namespace    Audio
function     void FMixerDevice::Get3DChannelMap

Source code excerpt:


				// Check for manual channel mapping parameters (LFE and Front Center)
				if (Channel == EAudioMixerChannel::LowFrequency)
				{
					EffectivePan = InWaveInstance->LFEBleed;
				}
				else if (Channel == PrevChannelInfo->Channel)
				{
					EffectivePan = PrevChannelPan;

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixer/Public/AudioMixerBlueprintLibrary.h:60

Scope: file

Source code excerpt:

	FrontRight,
	FrontCenter,
	LowFrequency,
	BackLeft,
	BackRight,
	FrontLeftOfCenter,
	FrontRightOfCenter,
	BackCenter,
	SideLeft,

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixer/Public/AudioMixerBlueprintLibrary.h:87

Scope (from outer to inner):

file
function     inline const TCHAR* ToString

Source code excerpt:

		case EAudioMixerChannelType::FrontRight:			return TEXT("FrontRight");
		case EAudioMixerChannelType::FrontCenter:			return TEXT("FrontCenter");
		case EAudioMixerChannelType::LowFrequency:			return TEXT("LowFrequency");
		case EAudioMixerChannelType::BackLeft:				return TEXT("BackLeft");
		case EAudioMixerChannelType::BackRight:				return TEXT("BackRight");
		case EAudioMixerChannelType::FrontLeftOfCenter:		return TEXT("FrontLeftOfCenter");
		case EAudioMixerChannelType::FrontRightOfCenter:	return TEXT("FrontRightOfCenter");
		case EAudioMixerChannelType::BackCenter:			return TEXT("BackCenter");
		case EAudioMixerChannelType::SideLeft:				return TEXT("SideLeft");

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixerCore/Private/AudioMixer.cpp:812

Scope (from outer to inner):

file
namespace    Audio
function     static void InitializeDefaultChannelOrder

Source code excerpt:

		DefaultChannelOrder[1] = EAudioMixerChannel::FrontRight;
		DefaultChannelOrder[2] = EAudioMixerChannel::FrontCenter;
		DefaultChannelOrder[3] = EAudioMixerChannel::LowFrequency;
		DefaultChannelOrder[4] = EAudioMixerChannel::SideLeft;
		DefaultChannelOrder[5] = EAudioMixerChannel::SideRight;
		DefaultChannelOrder[6] = EAudioMixerChannel::BackLeft;
		DefaultChannelOrder[7] = EAudioMixerChannel::BackRight;

		bool bOverridden = false;

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixerCore/Public/AudioMixer.h:82

Scope (from outer to inner):

file
namespace    EAudioMixerChannel

Source code excerpt:

		FrontRight,
		FrontCenter,
		LowFrequency,
		BackLeft,
		BackRight,
		FrontLeftOfCenter,
		FrontRightOfCenter,
		BackCenter,
		SideLeft,

#Loc: <Workspace>/Engine/Source/Runtime/AudioMixerCore/Public/AudioMixer.h:111

Scope (from outer to inner):

file
namespace    EAudioMixerChannel
function     inline const TCHAR* ToString

Source code excerpt:

		case FrontRight:			return TEXT("FrontRight");
		case FrontCenter:			return TEXT("FrontCenter");
		case LowFrequency:			return TEXT("LowFrequency");
		case BackLeft:				return TEXT("BackLeft");
		case BackRight:				return TEXT("BackRight");
		case FrontLeftOfCenter:		return TEXT("FrontLeftOfCenter");
		case FrontRightOfCenter:	return TEXT("FrontRightOfCenter");
		case BackCenter:			return TEXT("BackCenter");
		case SideLeft:				return TEXT("SideLeft");

#Loc: <Workspace>/Engine/Source/Runtime/MediaUtils/Private/MediaAudioResampler.cpp:137

Scope (from outer to inner):

file
namespace    MediaAudioResampler

Source code excerpt:

		0.0f,		// FrontRight
		1.0f,		// Center
		0.0f,		// LowFrequency
		0.0f,		// SideLeft
		0.0f,		// SideRight
		0.0f,		// BackLeft
		0.0f,		// BackRight
	};

#Loc: <Workspace>/Engine/Source/Runtime/MediaUtils/Private/MediaAudioResampler.cpp:149

Scope (from outer to inner):

file
namespace    MediaAudioResampler

Source code excerpt:

		0.0f,			1.0f,			// FrontRight
		0.0f,			0.0f,			// Center
		0.0f,			0.0f,			// LowFrequency
		0.0f,			0.0f,			// SideLeft
		0.0f,			0.0f,			// SideRight
		0.0f,			0.0f,			// BackLeft
		0.0f,			0.0f,			// BackRight
	};

#Loc: <Workspace>/Engine/Source/Runtime/MediaUtils/Private/MediaAudioResampler.cpp:161

Scope (from outer to inner):

file
namespace    MediaAudioResampler

Source code excerpt:

		0.0f,			1.0f,		0.0f,	// FrontRight
		0.0f,			0.0f,		1.0f,	// Center
		0.0f,			0.0f,		0.0f,	// LowFrequency
		0.0f,			0.0f,		0.0f,	// SideLeft
		0.0f,			0.0f,		0.0f,	// SideRight
		0.0f,			0.0f,		0.0f,	// BackLeft
		0.0f,			0.0f,		0.0f,	// BackRight
	};

#Loc: <Workspace>/Engine/Source/Runtime/MediaUtils/Private/MediaAudioResampler.cpp:173

Scope (from outer to inner):

file
namespace    MediaAudioResampler

Source code excerpt:

		0.0f,			1.0f,		0.0f,		0.0f,		// FrontRight
		0.0f,			0.0f,		0.0f,		0.0f,		// Center
		0.0f,			0.0f,		0.0f,		0.0f,		// LowFrequency
		0.0f,			0.0f,		1.0f,		0.0f,		// SideLeft
		0.0f,			0.0f,		0.0f,		1.0f,		// SideRight
		0.0f,			0.0f,		0.0f,		0.0f,		// BackLeft
		0.0f,			0.0f,		0.0f,		0.0f,		// BackRight
	};

#Loc: <Workspace>/Engine/Source/Runtime/MediaUtils/Private/MediaAudioResampler.cpp:185

Scope (from outer to inner):

file
namespace    MediaAudioResampler

Source code excerpt:

		0.0f,			1.0f,		0.0f,		0.0f,		0.0f,		// FrontRight
		0.0f,			0.0f,		1.0f,		0.0f,		0.0f,		// Center
		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// LowFrequency
		0.0f,			0.0f,		0.0f,		1.0f,		0.0f,		// SideLeft
		0.0f,			0.0f,		0.0f,		0.0f,		1.0f,		// SideRight
		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// BackLeft
		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// BackRight
	};

#Loc: <Workspace>/Engine/Source/Runtime/MediaUtils/Private/MediaAudioResampler.cpp:197

Scope (from outer to inner):

file
namespace    MediaAudioResampler

Source code excerpt:

		0.0f,			1.0f,		0.0f,		0.0f,		0.0f,		0.0f,		// FrontRight
		0.0f,			0.0f,		1.0f,		0.0f,		0.0f,		0.0f,		// Center
		0.0f,			0.0f,		0.0f,		1.0f,		0.0f,		0.0f,		// LowFrequency
		0.0f,			0.0f,		0.0f,		0.0f,		1.0f,		0.0f,		// SideLeft
		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		1.0f,		// SideRight
		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		0.0f,		// BackLeft
		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		0.0f,		// BackRight
	};

#Loc: <Workspace>/Engine/Source/Runtime/MediaUtils/Private/MediaAudioResampler.cpp:209

Scope (from outer to inner):

file
namespace    MediaAudioResampler

Source code excerpt:

		0.0f,			1.0f,		0.0f,		0.0f,		0.0f,		0.0f,		0.0f,		// FrontRight
		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		0.0f,		0.0f,		// Center
		0.0f,			0.0f,		0.0f,		1.0f,		0.0f,		0.0f,		0.0f,		// LowFrequency
		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		1.0f,		0.0f,		// SideLeft
		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		0.0f,		1.0f,		// SideRight
		0.0f,			0.0f,		1.0f,		0.0f,		0.0f,		0.0f,		0.0f,		// BackLeft
		0.0f,			0.0f,		0.0f,		0.0f,		1.0f,		0.0f,		0.0f,		// BackRight
	};

#Loc: <Workspace>/Engine/Source/Runtime/MediaUtils/Private/MediaAudioResampler.cpp:221

Scope (from outer to inner):

file
namespace    MediaAudioResampler

Source code excerpt:

		0.0f,			1.0f,		0.0f,		0.0f,		0.0f,		0.0f,		0.0f,		0.0f,		// FrontRight
		0.0f,			0.0f,		1.0f,		0.0f,		0.0f,		0.0f,		0.0f,		0.0f,		// Center
		0.0f,			0.0f,		0.0f,		1.0f,		0.0f,		0.0f,		0.0f,		0.0f,		// LowFrequency
		0.0f,			0.0f,		0.0f,		0.0f,		1.0f,		0.0f,		0.0f,		0.0f,		// SideLeft
		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		1.0f,		0.0f,		0.0f,		// SideRight
		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		0.0f,		1.0f,		0.0f,		// BackLeft
		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		0.0f,		0.0f,		1.0f,		// BackRight
	};

#Loc: <Workspace>/Engine/Source/Runtime/NonRealtimeAudioRenderer/Private/AudioMixerPlatformNonRealtime.cpp:167

Scope (from outer to inner):

file
namespace    Audio
function     bool FMixerPlatformNonRealtime::GetOutputDeviceInfo

Source code excerpt:

		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::FrontRight);
		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::FrontCenter);
		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::LowFrequency);
		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::BackLeft);
		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::BackRight);
		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::SideLeft);
		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::SideRight);

		return true;

#Loc: <Workspace>/Engine/Source/Runtime/SignalProcessing/Private/ChannelMap.cpp:12

Scope (from outer to inner):

file
namespace    Audio
namespace    ChannelMapPrivate

Source code excerpt:

		static constexpr float ToMonoMatrix[ChannelMapMaxNumChannels * 1] =
		{
			// FrontLeft	FrontRight	Center		LowFrequency	SideLeft	SideRight	BackLeft	BackRight  
			0.707f,			0.707f,		1.0f,		0.0f,			0.5f,		0.5f,		0.5f,		0.5f,		// FrontLeft
		};

		static constexpr float VorbisToMonoMatrix[ChannelMapVorbisNumChannels * 1] =
		{
			// FrontLeft	Center		FrontRight	SideLeft		SideRight	LowFrequency		
			0.707f,			1.0f,		0.707f,		0.5f,			0.5f,		0.0f,		// FrontLeft
		};

		static constexpr float ToStereoMatrix[ChannelMapMaxNumChannels * 2] =
		{
			// FrontLeft	FrontRight	Center		LowFrequency	SideLeft	SideRight	BackLeft	BackRight  
			1.0f,			0.0f,		0.707f,		0.0f,			0.707f,		0.0f,		0.707f,		0.0f,		// FrontLeft
			0.0f,			1.0f,		0.707f,		0.0f,			0.0f,		0.707f,		0.0f,		0.707f,		// FrontRight
		};

		static constexpr float VorbisToStereoMatrix[ChannelMapVorbisNumChannels * 2] =
		{
			// FrontLeft	Center		FrontRight	SideLeft		SideRight	LowFrequency		
			1.0f,			0.707f,		0.0f,		0.707f,			0.0f,		0.0f,		// FrontLeft
			0.0f,			0.707f,		1.0f,		0.0f,			0.707f,		0.0f,		// FrontRight
		};

		static constexpr float ToTriMatrix[ChannelMapMaxNumChannels * 3] =
		{
			// FrontLeft	FrontRight	Center		LowFrequency	SideLeft	SideRight	BackLeft	BackRight  
			1.0f,			0.0f,		0.0f,		0.0f,			0.707f,		0.0f,		0.707f,		0.0f,		// FrontLeft
			0.0f,			1.0f,		0.0f,		0.0f,			0.0f,		0.707f,		0.0f,		0.707f,		// FrontRight
			0.0f,			0.0f,		1.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// Center
		};

		static constexpr float VorbisToTriMatrix[ChannelMapVorbisNumChannels * 3] =
		{
			// FrontLeft	Center		FrontRight	SideLeft		SideRight	LowFrequency		
			1.0f,			0.0f,		0.0f,		0.707f,			0.0f,		0.0f,		// FrontLeft
			0.0f,			0.0f,		1.0f,		0.0f,			0.707f,		0.0f,		// FrontRight
			0.0f,			1.0f,		0.0f,		0.0f,			0.0f,		0.0f,		// Center
		};

		static constexpr float ToQuadMatrix[ChannelMapMaxNumChannels * 4] =
		{
			// FrontLeft	FrontRight	Center		LowFrequency	SideLeft	SideRight	BackLeft	BackRight	
			1.0f,			0.0f,		0.707f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontLeft
			0.0f,			1.0f,		0.707f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontRight
			0.0f,			0.0f,		0.0f,		0.0f,			1.0f,		0.0f,		1.0f,		0.0f,		// SideLeft
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		1.0f,		0.0f,		1.0f,		// SideRight
		};

		static constexpr float VorbisToQuadMatrix[ChannelMapVorbisNumChannels * 4] =
		{
			// FrontLeft	Center		FrontRight	SideLeft		SideRight	LowFrequency		
			1.0f,			0.707f,		0.0f,		0.0f,			0.0f,		0.0f,		// FrontLeft
			0.0f,			0.707f,		1.0f,		0.0f,			0.0f,		0.0f,		// FrontRight
			0.0f,			0.0f,		0.0f,		1.0f,			0.0f,		0.0f,		// SideLeft
			0.0f,			0.0f,		0.0f,		0.0f,			1.0f,		0.0f,		// SideRight
		};

		static constexpr float To5Matrix[ChannelMapMaxNumChannels * 5] =
		{
			// FrontLeft	FrontRight	Center		LowFrequency	SideLeft	SideRight	BackLeft	BackRight	
			1.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontLeft
			0.0f,			1.0f,		0.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontRight
			0.0f,			0.0f,		1.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// Center
			0.0f,			0.0f,		0.0f,		0.0f,			1.0f,		0.0f,		1.0f,		0.0f,		// SideLeft
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		1.0f,		0.0f,		1.0f,		// SideRight
		};

#Loc: <Workspace>/Engine/Source/Runtime/SignalProcessing/Private/ChannelMap.cpp:82

Scope (from outer to inner):

file
namespace    Audio
namespace    ChannelMapPrivate

Source code excerpt:

		static constexpr float VorbisTo5Matrix[ChannelMapVorbisNumChannels * 5] =
		{
			// FrontLeft	Center		FrontRight	SideLeft		SideRight	LowFrequency		
			1.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		// FrontLeft
			0.0f,			0.0f,		1.0f,		0.0f,			0.0f,		0.0f,		// FrontRight
			0.0f,			1.0f,		0.0f,		0.0f,			0.0f,		0.0f,		// Center
			0.0f,			0.0f,		0.0f,		1.0f,			0.0f,		0.0f,		// SideLeft
			0.0f,			0.0f,		0.0f,		0.0f,			1.0f,		0.0f,		// SideRight
		};

#Loc: <Workspace>/Engine/Source/Runtime/SignalProcessing/Private/ChannelMap.cpp:92

Scope (from outer to inner):

file
namespace    Audio
namespace    ChannelMapPrivate

Source code excerpt:

		static constexpr float To5Point1Matrix[ChannelMapMaxNumChannels * 6] =
		{
			// FrontLeft	FrontRight	Center		LowFrequency	SideLeft	SideRight	BackLeft	BackRight	
			1.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontLeft
			0.0f,			1.0f,		0.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontRight
			0.0f,			0.0f,		1.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// Center
			0.0f,			0.0f,		0.0f,		1.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// LowFrequency
			0.0f,			0.0f,		0.0f,		0.0f,			1.0f,		0.0f,		1.0f,		0.0f,		// SideLeft
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		1.0f,		0.0f,		1.0f,		// SideRight
		};

		static constexpr float VorbisTo5Point1Matrix[ChannelMapVorbisNumChannels * 6] =
		{
			// FrontLeft	Center		FrontRight	SideLeft		SideRight	LowFrequency	
			1.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		// FrontLeft
			0.0f,			0.0f,		1.0f,		0.0f,			0.0f,		0.0f,		// FrontRight
			0.0f,			1.0f,		0.0f,		0.0f,			0.0f,		0.0f,		// Center
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		1.0f,		// LowFrequency
			0.0f,			0.0f,		0.0f,		1.0f,			0.0f,		0.0f,		// SideLeft
			0.0f,			0.0f,		0.0f,		0.0f,			1.0f,		0.0f,		// SideRight
		};

		static constexpr float ToHexMatrix[ChannelMapMaxNumChannels * 7] =
		{
			// FrontLeft	FrontRight	Center		LowFrequency	SideLeft	SideRight	BackLeft	BackRight	
			1.0f,			0.0f,		0.707f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontLeft
			0.0f,			1.0f,		0.707f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontRight
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		1.0f,		0.0f,		// BackLeft
			0.0f,			0.0f,		0.0f,		1.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// LFE
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		0.0f,		1.0f,		// BackRight
			0.0f,			0.0f,		0.0f,		0.0f,			1.0f,		0.0f,		0.0f,		0.0f,		// SideLeft

#Loc: <Workspace>/Engine/Source/Runtime/SignalProcessing/Private/ChannelMap.cpp:126

Scope (from outer to inner):

file
namespace    Audio
namespace    ChannelMapPrivate

Source code excerpt:

		static constexpr float VorbisToHexMatrix[ChannelMapVorbisNumChannels * 7] =
		{
			// FrontLeft	Center		FrontRight	SideLeft		SideRight	LowFrequency	
			1.0f,			0.707f,		0.0f,		0.0f,			0.0f,		0.0f,		// FrontLeft
			0.0f,			0.707f,		1.0f,		0.0f,			0.0f,		0.0f,		// FrontRight
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		// BackLeft
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		1.0f,		// LFE
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		// BackRight
			0.0f,			0.0f,		0.0f,		1.0f,			0.0f,		0.0f,		// SideLeft

#Loc: <Workspace>/Engine/Source/Runtime/SignalProcessing/Private/ChannelMap.cpp:140

Scope (from outer to inner):

file
namespace    Audio
namespace    ChannelMapPrivate

Source code excerpt:

		static constexpr float To7Point1Matrix[ChannelMapMaxNumChannels * 8] =
		{
			// FrontLeft	FrontRight	Center		LowFrequency	SideLeft	SideRight	BackLeft	BackRight
			1.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontLeft
			0.0f,			1.0f,		0.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontRight
			0.0f,			0.0f,		1.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontCenter
			0.0f,			0.0f,		0.0f,		1.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// LowFrequency
			0.0f,			0.0f,		0.0f,		0.0f,			1.0f,		0.0f,		0.0f,		0.0f,		// SideLeft
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		1.0f,		0.0f,		0.0f,		// SideRight
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		1.0f,		0.0f,		// BackLeft
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		0.0f,		1.0f,		// BackRight
		};

#Loc: <Workspace>/Engine/Source/Runtime/SignalProcessing/Private/ChannelMap.cpp:156

Scope (from outer to inner):

file
namespace    Audio
namespace    ChannelMapPrivate

Source code excerpt:

		static constexpr float To7Point1Matrix[ChannelMapMaxNumChannels * 8] =
		{
			// FrontLeft	FrontRight	Center		LowFrequency	SideLeft	SideRight	BackLeft	BackRight
			1.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontLeft
			0.0f,			1.0f,		0.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontRight
			0.0f,			0.0f,		1.0f,		0.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// FrontCenter
			0.0f,			0.0f,		0.0f,		1.0f,			0.0f,		0.0f,		0.0f,		0.0f,		// LowFrequency
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		1.0f,		0.0f,		// BackLeft
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		0.0f,		1.0f,		// BackRight
			0.0f,			0.0f,		0.0f,		0.0f,			1.0f,		0.0f,		0.0f,		0.0f,		// SideLeft
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		1.0f,		0.0f,		0.0f,		// SideRight
		};

#Loc: <Workspace>/Engine/Source/Runtime/SignalProcessing/Private/ChannelMap.cpp:171

Scope (from outer to inner):

file
namespace    Audio
namespace    ChannelMapPrivate

Source code excerpt:

		static constexpr float VorbisTo7Point1Matrix[ChannelMapVorbisNumChannels * 8] =
		{
			// FrontLeft	Center		FrontRight	SideLeft		SideRight	LowFrequency		
			1.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		// FrontLeft
			0.0f,			0.0f,		1.0f,		0.0f,			0.0f,		0.0f,		// FrontRight
			0.0f,			1.0f,		0.0f,		0.0f,			0.0f,		0.0f,		// FrontCenter
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		1.0f,		// LowFrequency
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		// SideLeft
			0.0f,			0.0f,		0.0f,		0.0f,			0.0f,		0.0f,		// SideRight
			0.0f,			0.0f,		0.0f,		1.0f,			0.0f,		0.0f,		// BackLeft
			0.0f,			0.0f,		0.0f,		0.0f,			1.0f,		0.0f,		// BackRight
		};

#Loc: <Workspace>/Engine/Source/Runtime/SoundFieldRendering/Private/SoundFieldRendering.cpp:29

Scope (from outer to inner):

file
function     FSoundFieldDecoder::FSoundFieldDecoder

Source code excerpt:


		// (skip LFE)
		if (CurrSpeakerPos.Channel == EAudioMixerChannel::LowFrequency)
		{
			SpeakerGainsPtr += NumAmbiChannels;
			continue;
		}

		const float Azimuth = CurrSpeakerPos.Azimuth * DEG_2_RAD;

#Loc: <Workspace>/Engine/Source/Runtime/SoundFieldRendering/Private/SoundFieldRendering.cpp:157

Scope (from outer to inner):

file
function     void FSoundFieldDecoder::DecodeAudioDirectlyToDeviceOutputPositions

Source code excerpt:


		// skip LFE and Center channel (leave gains at zero)
		if (CurrSpeakerPos.Channel == EAudioMixerChannel::LowFrequency || CurrSpeakerPos.Channel == EAudioMixerChannel::FrontCenter)
		{
			SpeakerGainsPtr += NumAmbiChannels;
			continue;
		}

		const float Theta = ListenerRotationSphericalCoord.X - CurrSpeakerPos.Azimuth * DEG_2_RAD; // azimuth

#Loc: <Workspace>/Engine/Source/Runtime/SoundFieldRendering/Private/SoundFieldRendering.cpp:687

Scope: file

Source code excerpt:

	,{EAudioMixerChannel::FrontRight, 30, 0}
	,{EAudioMixerChannel::FrontCenter, 0, 0}
	,{EAudioMixerChannel::LowFrequency, -1, 0}
	,{EAudioMixerChannel::BackLeft, 210, 0} 
	,{EAudioMixerChannel::BackRight, 150, 0}
	,{EAudioMixerChannel::SideLeft, 250, 0}
	,{EAudioMixerChannel::SideRight, 110, 0}
	,{EAudioMixerChannel::BackCenter, 180,0}
};

#Loc: <Workspace>/Engine/Source/Runtime/SoundFieldRendering/Private/SoundFieldRendering.cpp:740

Scope (from outer to inner):

file
function     void FSoundFieldEncoder::EncodeAudioDirectlyFromOutputPositions

Source code excerpt:

		// skip LFE and Center channel (leave gains at zero)
		// Mono audio channels are FrontCenter, so do _not_ skip if center channel and mono.
		const bool bSkipChannel = CurrSpeakerPos.Channel == EAudioMixerChannel::LowFrequency || (!bIsMono && (CurrSpeakerPos.Channel == EAudioMixerChannel::FrontCenter));
			
		if (bSkipChannel)
		{
			SpeakerGainsPtr += NumAmbiChannels;
			continue;
		}

#Loc: <Workspace>/Engine/Source/Runtime/Windows/AudioMixerXAudio2/Private/AudioMixerPlatformXAudio2.cpp:857

Scope (from outer to inner):

file
namespace    Audio
function     static bool GetMMDeviceInfo

Source code excerpt:

					EAudioMixerChannel::FrontRight,
					EAudioMixerChannel::FrontCenter,
					EAudioMixerChannel::LowFrequency,
					EAudioMixerChannel::SideLeft,
					EAudioMixerChannel::SideRight,
					EAudioMixerChannel::BackLeft,
					EAudioMixerChannel::BackRight,
				};

#Loc: <Workspace>/Engine/Source/Runtime/Windows/AudioMixerXAudio2/Private/AudioMixerPlatformXAudio2.cpp:884

Scope (from outer to inner):

file
namespace    Audio
function     static bool GetMMDeviceInfo

Source code excerpt:

						EAudioMixerChannel::FrontRight,
						EAudioMixerChannel::FrontCenter,
						EAudioMixerChannel::LowFrequency,
						EAudioMixerChannel::BackLeft,
						EAudioMixerChannel::BackRight,
					};

					ChannelOrdering = DefaultChannelOrdering51;
				}

#Loc: <Workspace>/Engine/Source/Runtime/Windows/AudioMixerXAudio2/Private/AudioMixerPlatformXAudio2.cpp:1035

Scope (from outer to inner):

file
namespace    Audio
function     bool FMixerPlatformXAudio2::GetOutputDeviceInfo

Source code excerpt:

		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::FrontRight);
		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::FrontCenter);
		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::LowFrequency);
		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::BackLeft);
		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::BackRight);
		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::SideLeft);
		OutInfo.OutputChannelArray.Add(EAudioMixerChannel::SideRight);
		return true;
#endif

#Loc: <Workspace>/Engine/Source/Runtime/Windows/AudioMixerXAudio2/Private/WindowsMMDeviceInfoCache.cpp:133

Scope (from outer to inner):

file
namespace    Audio
function     bool FWindowsMMDeviceCache::EnumerateChannelMask

Source code excerpt:

			EAudioMixerChannel::FrontRight,
			EAudioMixerChannel::FrontCenter,
			EAudioMixerChannel::LowFrequency,
			EAudioMixerChannel::SideLeft,
			EAudioMixerChannel::SideRight,
			EAudioMixerChannel::BackLeft,
			EAudioMixerChannel::BackRight,
		};

#Loc: <Workspace>/Engine/Source/Runtime/Windows/AudioMixerXAudio2/Private/WindowsMMDeviceInfoCache.cpp:160

Scope (from outer to inner):

file
namespace    Audio
function     bool FWindowsMMDeviceCache::EnumerateChannelMask

Source code excerpt:

				EAudioMixerChannel::FrontRight,
				EAudioMixerChannel::FrontCenter,
				EAudioMixerChannel::LowFrequency,
				EAudioMixerChannel::BackLeft,
				EAudioMixerChannel::BackRight,
			};

			ChannelOrdering = DefaultChannelOrdering51;
		}