AudioStreamGenerator | Godot Docs 4.4

class-description

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Object

AudioStreamGenerator

An audio stream with utilities for procedural sound generation.

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.
var phase = 0.0

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

func fill_buffer():
    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)

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.

Enum

AudioStreamGeneratorMixRate

()

:Enum

MIX_RATE_OUTPUT = 0

Current AudioServer output mixing rate.

MIX_RATE_INPUT = 1

Current AudioServer input mixing rate.

MIX_RATE_CUSTOM = 2

Custom mixing rate, specified by mix_rate.

MIX_RATE_MAX = 3

Maximum value for the mixing rate mode enum.

float

buffer_length

()

:float

The length of the buffer to generate (in seconds). Lower values result in less latency, but require the script to generate audio data faster, resulting in increased CPU usage and more risk for audio cracking if the CPU can't keep up.

float

mix_rate

()

:float

The sample rate to use (in Hz). Higher values are more demanding for the CPU to generate, but result in better quality.

In games, common sample rates in use are 11025, 16000, 22050, 32000, 44100, and 48000.

According to the Nyquist-Shannon sampling theorem, there is no quality difference to human hearing when going past 40,000 Hz (since most humans can only hear up to ~20,000 Hz, often less). If you are generating lower-pitched sounds such as voices, lower sample rates such as 32000 or 22050 may be usable with no loss in quality.

Note: AudioStreamGenerator is not automatically resampling input data, to produce expected result mix_rate_mode should match the sampling rate of input data.

Note: If you are using AudioEffectCapture as the source of your data, set mix_rate_mode to MIX_RATE_INPUT or MIX_RATE_OUTPUT to automatically match current AudioServer mixing rate.

AudioStreamGeneratorMixRate

mix_rate_mode

()

:AudioStreamGeneratorMixRate

Mixing rate mode. If set to MIX_RATE_CUSTOM, mix_rate is used, otherwise current AudioServer mixing rate is used.