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AudioStreamGenerator¶

Inherits: AudioStream < Resource < RefCounted < Object

An audio stream with utilities for procedural sound generation.

Description¶

AudioStreamGenerator is a type of audio stream that does not play back sounds on its own; instead, it expects a script to generate audio data for it. See also AudioStreamGeneratorPlayback.

Here's a sample on how to use it to generate a sine wave:

var playback # Will hold the AudioStreamGeneratorPlayback.
@onready var sample_hz = $AudioStreamPlayer.stream.mix_rate
var pulse_hz = 440.0 # The frequency of the sound wave.

func _ready():
    $AudioStreamPlayer.play()
    playback = $AudioStreamPlayer.get_stream_playback()
    fill_buffer()

func fill_buffer():
    var phase = 0.0
    var increment = pulse_hz / sample_hz
    var frames_available = playback.get_frames_available()

    for i in range(frames_available):
        playback.push_frame(Vector2.ONE * sin(phase * TAU))
        phase = fmod(phase + increment, 1.0)

[Export] public AudioStreamPlayer Player { get; set; }

private AudioStreamGeneratorPlayback _playback; // Will hold the AudioStreamGeneratorPlayback.
private float _sampleHz;
private float _pulseHz = 440.0f; // The frequency of the sound wave.

public override void _Ready()
{
    if (Player.Stream is AudioStreamGenerator generator) // Type as a generator to access MixRate.
    {
        _sampleHz = generator.MixRate;
        Player.Play();
        _playback = (AudioStreamGeneratorPlayback)Player.GetStreamPlayback();
        FillBuffer();
    }
}

public void FillBuffer()
{
    double phase = 0.0;
    float increment = _pulseHz / _sampleHz;
    int framesAvailable = _playback.GetFramesAvailable();

    for (int i = 0; i < framesAvailable; i++)
    {
        _playback.PushFrame(Vector2.One * (float)Mathf.Sin(phase * Mathf.Tau));
        phase = Mathf.PosMod(phase + increment, 1.0);
    }
}

In the example above, the "AudioStreamPlayer" node must use an AudioStreamGenerator as its stream. The fill_buffer function provides audio data for approximating a sine wave.

See also AudioEffectSpectrumAnalyzer for performing real-time audio spectrum analysis.

Note: Due to performance constraints, this class is best used from C# or from a compiled language via GDExtension. If you still want to use this class from GDScript, consider using a lower mix_rate such as 11,025 Hz or 22,050 Hz.

Tutorials¶

Audio Generator Demo

Properties¶

float	buffer_length	`0.5`
float	mix_rate	`44100.0`

Property Descriptions¶

float buffer_length =