- Qt 6.4
- Qt Spatial Audio
- C++ Classes
- QtSpatialAudio
- QAudioEngine
- Technology Preview

# QAudioEngine Class

QAudioEngine manages a three dimensional sound field. More...

Header: | #include <QAudioEngine>
CMake: | find_package(Qt6 REQUIRED COMPONENTS SpatialAudio) target_link_libraries(mytarget PRIVATE Qt6::SpatialAudio)
qmake: | QT += spatialaudio

- List of all members, including inherited members

## Public Types

enum | OutputMode { Surround, Stereo, Headphone }

## Properties

- distanceScale : float
- masterVolume : float
- outputDevice : QAudioDevice

- outputMode : OutputMode
- paused : bool

## Public Functions

| QAudioEngine(int sampleRate, QObject *parent = nullptr)
| QAudioEngine(QObject *parent)
| QAudioEngine()
virtual | ~QAudioEngine()
float | distanceScale() const
float | masterVolume() const
QAudioDevice | outputDevice() const
QAudioEngine::OutputMode | outputMode() const
bool | paused() const
bool | roomEffectsEnabled() const
int | sampleRate() const
void | setDistanceScale(float scale)
void | setMasterVolume(float volume)
void | setOutputDevice(const QAudioDevice &device)
void | setOutputMode(QAudioEngine::OutputMode mode)
void | setPaused(bool paused)
void | setRoomEffectsEnabled(bool enabled)

## Public Slots

void | pause()
void | resume()
void | start()
void | stop()

## Signals

void | distanceScaleChanged()
void | masterVolumeChanged()
void | outputDeviceChanged()
void | outputModeChanged()
void | pausedChanged()

## Detailed Description

You can use an instance of QAudioEngine to manage a sound field in three dimensions. A sound field is defined by several QSpatialSound objects that define a sound at a specified location in 3D space. You can also add stereo overlays using QAmbientSound.

You can use QAudioListener to define the position of the person listening to the sound field relative to the sound sources. Sound sources will be less audible if the listener is further away from source. They will also get mapped to the corresponding loudspeakers depending on the direction between listener and source.

QAudioEngine offers two output modes. The first mode renders the sound field to a set of speakers, either a stereo speaker pair or a surround configuration. The second mode provides an immersive 3D sound experience when using headphones.

Perception of sound localization is driven mainly by two factors. The first factor is timing differences of the sound waves between left and right ear. The second factor comes from various ways how sounds coming from different direcations create different types of reflections from our ears and heads. See https://en.wikipedia.org/wiki/Sound_localization for more details.

The spatial audio engine emulates those timing differences and reflections through Head related transfer functions (HRTF, see https://en.wikipedia.org/wiki/Head-related_transfer_function). The functions used emulates those effects for an average persons ears and head. It provides a good and immersive 3D sound localization experience for most persons when using headphones.

The engine is rather versatile allowing you to define room properties and reverb settings to emulate different types of rooms.

Sound sources can also be occluded dampening the sound coming from those sources.

The audio engine uses a coordinate system that is in centimeters by default. The axes are aligned with the typical coordinate system used in 3D. Positive x points to the right, positive y points up and positive z points backwards.

## Member Type Documentation

### enum QAudioEngine::OutputMode

Constant | Value | Description
--- | --- | ---
`QAudioEngine::Surround` | `0` | Map the sounds to the loudspeaker configuration of the output device. This is normally a stereo or surround speaker setup.
`QAudioEngine::Stereo` | `1` | Map the sounds to the stereo loudspeaker configuration of the output device. This will ignore any additional speakers and only use the left and right channels to create a stero rendering of the sound field.
`QAudioEngine::Headphone` | `2` | Use Headphone spatialization to create a 3D audio effect when listening to the sound field through headphones

## Property Documentation

### distanceScale : float

Defines the scale of the coordinate system being used by the spatial audio engine. By default, all units are in centimeters, in line with the default units being used by Qt Quick 3D.

Set the distance scale to QAudioEngine::DistanceScaleMeter to get units in meters.

Access functions:

float | distanceScale() const
void | setDistanceScale(float scale)

Notifier signal:

void | distanceScaleChanged()

### masterVolume : float

Sets or returns volume being used to render the sound field.

Access functions:

float | masterVolume() const
void | setMasterVolume(float volume)

Notifier signal:

void | masterVolumeChanged()

### outputDevice : QAudioDevice

Sets or returns the device that is being used for playing the sound field.

Access functions:

QAudioDevice | outputDevice() const
void | setOutputDevice(const QAudioDevice &device)

Notifier signal:

void | outputDeviceChanged()

### outputMode : OutputMode

Sets or retrieves the current output mode of the engine.

Access functions:

QAudioEngine::OutputMode | outputMode() const
void | setOutputMode(QAudioEngine::OutputMode mode)

Notifier signal:

void | outputModeChanged()

See also QAudioEngine::OutputMode.

### paused : bool

Pauses the spatial audio engine.

Access functions:

bool | paused() const
void | setPaused(bool paused)

Notifier signal:

void | pausedChanged()

## Member Function Documentation

### QAudioEngine::QAudioEngine()

### QAudioEngine::QAudioEngine(QObject *parent)

### QAudioEngine::QAudioEngine(int sampleRate, QObject *parent = nullptr)

Constructs a spatial audio engine with parent, if any.

The engine will operate with a sample rate given by sampleRate. The default sample rate, if none is provided, is 44100 (44.1kHz).

Sound content that is not provided at that sample rate will automatically get resampled to sampleRate when being processed by the engine. The default sample rate is fine in most cases, but you can define a different rate if most of your sound files are sampled with a different rate, and avoid some CPU overhead for resampling.

### `[slot]` void QAudioEngine::pause()

Pauses playback.

### `[slot]` void QAudioEngine::resume()

Resumes playback.

### `[slot]` void QAudioEngine::start()

Starts the engine.

### `[slot]` void QAudioEngine::stop()

Stops the engine.

### `[virtual]` QAudioEngine::~QAudioEngine()

Destroys the spatial audio engine.

### bool QAudioEngine::roomEffectsEnabled() const

Returns true if room effects are enabled.

See also setRoomEffectsEnabled().

### int QAudioEngine::sampleRate() const

Returns the sample rate the engine has been configured with.

### void QAudioEngine::setRoomEffectsEnabled(bool enabled)

Enables room effects such as echos and reverb.

Enables room effects if enabled is true. Room effects will only apply if you create one or more QAudioRoom objects and the listener is inside at least one of the rooms. If the listener is inside multiple rooms, the room with the smallest volume will be used.

See also roomEffectsEnabled().