AudioEngine

The AudioEngine is the main interface to library. The AudioEngine is responsible for loading and unloading SoundBanks, playing sounds, managing channel priorities, spawning and despawing Listeners, and more.

Initialization

To initialize the AudioEngine, you must specify an AudioConfig. You may either load one yourself or supply a path to an AudioConfig FlatBuffer binary. For example:

audio_engine_.Initialize("audio_config.bin");

Alternatively, you can also do this:

const AudioConfig* audio_config = GetAudioConfig();
audio_engine_.Initialize(audio_config);

Once the library is initialized, the AudioConfig object is no longer necessary and can be deallocated.

Main Loop

Once during every game loop there should be a call to AdvanceFrame. This is where the AudioEngine performs all prioritization and gain adjustments.

while (!GameOver()) {
  // ...
  float delta_time = SecondsSinceLastFrame();
  audio_engine_.AdvanceFrame(delta_time);
  // ...
}

Loading and Unloading Audio

Before any audio can be played, the associated SoundBank must be loaded into memory. Loading a SoundBank loads all SoundCollectionDefs listed in the file, making them available to be played.

To load a SoundBankDef simply call

audio_engine_.LoadSoundBank("path/to/soundbank.bin");

And when the SoundBank is no longer required you can unload it with

audio_engine_.UnloadSoundBank("path/to/soundbank.bin");

Playing Audio

Once a SoundCollectionDef has been loaded, it may be played with the following code:

Channel music_channel = audio_engine_.PlaySound("MenuMusic");

However, playing a sound in this way incurs a map lookup. If a sound is going to be played frequently, a handle may be cached to improve performance.

SoundHandle menu_music = audio_engine_.GetSoundHandle("MenuMusic");
Channel music_channel = audio_engine_.PlaySound(menu_music);

Positional and Nonpositional Audio

SoundCollectionDefs may be either positional or non-positional. When they are positional, the loudness of a channel is determined by its distance from the nearest Listener. Typically you will only need a single Listener, positioned at the camera, but in some cases (such as games with split screen multiplayer for example) it may be desirable to have more than one Listener. When there are more than one Listeners, only the distance from the nearest listener is considered. If there are no Listeners at all, all positional audio will be silent.

The maximum number of listeners is specified in the AudioConfig. Listeners can be spawned as follows:

Listener listener = audio_engine_.AddListener();

The location of the listener can be updated as often as is necessary. When a Listener is no longer needed it can be removed like so:

audio_engine_.RemoveListener(&listener);