looping buffer in AudioStreamPlayer

Help Audio
,
1

Godot Version

4.3

Question

Hello, I’m currently making a synthesizer in Godot and unfortunately I can’t loop a buffer without hearing a “pop” after the buffer is over
can anyone help me please?
my code:

extends Button

@onready var freq = $"/root/Global".notesdict[name]["freq"]
@onready var wave = "sine"#$"/root/Global".wave
@onready var sample_hz = $AudioStreamPlayer.stream.mix_rate
var playback : AudioStreamGeneratorPlayback

var buffer = []
var buffer_length = 0

var touchmouse : bool = false

func _on_mouse_entered():
	print("Mouse entered")
	touchmouse = true

func _on_mouse_exited():
	print("Mouse exited")
	touchmouse = false

func generate_buffer():
	var increment = freq / sample_hz
	var phase = 0.0
	buffer = []
	var frames_available = sample_hz * 2  # Erhöhte Buffer-Größe
	for i in range(frames_available):
		var value = 0.0
		match wave:
			"sine":
				value = sin(phase * TAU)
			"square":
				value = 1.0 if phase % 1.0 < 0.5 else -1.0
			"triangle":
				value = 2.0 * abs(2.0 * (phase - floor(phase + 0.5))) - 1.0
			"sawtooth":
				value = 2.0 * (phase - floor(phase + 0.5))
		buffer.append(Vector2.ONE * value)
		phase = fmod(phase + increment, 1.0)
	buffer_length = len(buffer)

func _ready() -> void:
	generate_buffer()

func fill_buffer():
	while playback.get_frames_available() > 0:
		playback.push_frame(buffer[playback.get_frames_available() % buffer_length])

func _process(delta: float) -> void:
	if Input.is_action_pressed("mousepressed") and touchmouse:
		if not $AudioStreamPlayer.is_playing():
			print("playing")
			$AudioStreamPlayer.play()
			playback = $AudioStreamPlayer.get_stream_playback()
		fill_buffer()
	else:
		$AudioStreamPlayer.stop()
2

Your fill buffer needs to keep a pointer to the buffer position. Because available frames may be a fixed amount that is smaller or larger then your buffer. And you start from the beginning each time you call the function.

3

What is the best way to implement and use a pointer for the buffer?

4

For Godot, it is an index to point at which element of the buffer array should be pushed next. (An int)

var buffer_idx : int = 0
func fill_buffer():
  var avail_frames = playback.get_frames_available()
  while avail_frames > 0:
    playback.push_frame(buffer[buffer_idx])
    buffer_idx = (buffer_idx + 1) % buffer_length
    avail_frames -= 1
1 Like
5

sorry for the late reply.
your code works partially, I still get a few clicks at some frequencies.

What am I doing wrong?

6

Could it be due to the generate buffer function?

7

If the pops are periodic at a constant rate, yes. If they are random probably not.

8

I haven’t looked at your waveform code but the waveform could have a discontinuity, and will cause a pop every buffer period.

A good way to debug this is to do an internal digital capture, recording Godot’s output and looking at the waveform in your favorite DAW. Audacity is free.