New example : Audio/mixed processor

examples/audio/mixed_processor/main.go

@@ -0,0 +1,155 @@
+/*******************************************************************************************
+*
+*   raylib [audio] example - Mixed audio processing
+*
+*   Example originally created with raylib 4.2, last time updated with raylib 4.2
+*
+*   Example contributed by hkc (@hatkidchan) and reviewed by Ramon Santamaria (@raysan5)
+*
+*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
+*   BSD-like license that allows static linking with closed source software
+*
+*   Copyright (c) 2023 hkc (@hatkidchan)
+*
+********************************************************************************************/
+package main
+
+import (
+	"fmt"
+	"math"
+
+	rl "github.com/gen2brain/raylib-go/raylib"
+)
+
+const (
+	screenWidth  = 800
+	screenHeight = 450
+)
+
+var exponent float32 = 1.0     // Audio exponentiation value
+var averageVolume [400]float32 // Average volume history
+
+func main() {
+	rl.InitWindow(screenWidth, screenHeight, "raylib [audio] example - processing mixed output")
+
+	rl.InitAudioDevice() // Initialize audio device
+	rl.AttachAudioMixedProcessor(ProcessAudio)
+
+	music := rl.LoadMusicStream("country.mp3")
+	sound := rl.LoadSound("coin.wav")
+
+	rl.PlayMusicStream(music)
+
+	rl.SetTargetFPS(60) // Set our game to run at 60 frames-per-second
+
+	// Main game loop
+	for !rl.WindowShouldClose() { // Detect window close button or ESC key
+		rl.UpdateMusicStream(music) // Update music buffer with new stream data
+
+		// Modify processing variables
+		if rl.IsKeyPressed(rl.KeyLeft) {
+			exponent -= 0.05
+		}
+		if rl.IsKeyPressed(rl.KeyRight) {
+			exponent += 0.05
+		}
+		if rl.IsKeyPressed(rl.KeyDown) {
+			exponent -= 0.25
+		}
+		if rl.IsKeyPressed(rl.KeyUp) {
+			exponent += 0.25
+		}
+
+		// Make sure that exponent stays between 0.5 and 3
+		exponent = clamp(exponent, 0.5, 3)
+
+		if rl.IsKeyPressed(rl.KeySpace) {
+			rl.PlaySound(sound)
+		}
+
+		// Draw
+		rl.BeginDrawing()
+
+		rl.ClearBackground(rl.RayWhite)
+
+		rl.DrawText("MUSIC SHOULD BE PLAYING!", 255, 150, 20, rl.LightGray)
+
+		rl.DrawText(fmt.Sprintf("EXPONENT = %.2f", exponent), 215, 180, 20, rl.LightGray)
+
+		rl.DrawRectangle(199, 199, 402, 34, rl.LightGray)
+		for i := int32(0); i < 400; i++ {
+			rl.DrawLine(201+i, 232-int32(averageVolume[i]*32), 201+i, 232, rl.Maroon)
+		}
+		rl.DrawRectangleLines(199, 199, 402, 34, rl.Gray)
+
+		rl.DrawText("PRESS SPACE TO PLAY OTHER SOUND", 200, 250, 20, rl.LightGray)
+		rl.DrawText("USE LEFT AND RIGHT ARROWS TO ALTER DISTORTION", 140, 280, 20, rl.LightGray)
+
+		rl.EndDrawing()
+	}
+
+	// De-Initialization
+	rl.UnloadMusicStream(music)                // Unload music stream buffers from RAM
+	rl.DetachAudioMixedProcessor(ProcessAudio) // Disconnect audio processor
+	rl.CloseAudioDevice()                      // Close audio device (music streaming is automatically stopped)
+
+	rl.CloseWindow() // Close window and OpenGL context
+}
+
+// ProcessAudio is the audio processing function
+func ProcessAudio(buffer []float32, frames int) {
+	var average float32 // Temporary average volume
+	maxFrame := frames / 2
+
+	// Each frame has 2 samples (left and right),
+	// so we should loop `frames / 2` times
+	for frame := 0; frame < maxFrame; frame++ {
+		left := &buffer[frame*2+0]  // Left channel
+		right := &buffer[frame*2+1] // Right channel
+
+		// Modify left and right channel samples with exponent
+		*left = pow(abs(*left), exponent) * sgn(*left)
+		*right = pow(abs(*right), exponent) * sgn(*right)
+
+		// Accumulating average volume
+		average += abs(*left) / float32(maxFrame)
+		average += abs(*right) / float32(maxFrame)
+	}
+
+	// Shift average volume history buffer to the left
+	for i := 0; i < 399; i++ {
+		averageVolume[i] = averageVolume[i+1]
+	}
+
+	// Add the new average value
+	averageVolume[399] = average
+}
+
+// Helper functions to make the code shorter
+// (using less type conversions)
+// (Golang: Please make the `math` package generic! This is ridiculous :-)
+func abs(value float32) float32 {
+	return float32(math.Abs(float64(value)))
+}
+
+func pow(value, exponent float32) float32 {
+	return float32(math.Pow(float64(value), float64(exponent)))
+}
+
+func sgn(value float32) float32 {
+	if value < 0 {
+		return -1
+	} else if value > 0 {
+		return 1
+	}
+	return 0
+}
+func clamp(value, min, max float32) float32 {
+	if value < min {
+		return min
+	}
+	if value > max {
+		return max
+	}
+	return value
+}