sound

makefile

@@ -0,0 +1,26 @@
+SHELL=/bin/sh
+CC=gcc
+
+APP_NAME=synthesizer
+
+SRC=src
+BUILD=build
+
+C_FILES := $(shell find $(SRC) -name '*.c')
+O_FILES += $(patsubst $(SRC)/%.c, $(BUILD)/%.o, $(C_FILES))
+
+CFLAGS := -O0 -march=native -std=gnu99
+INCLUDE := 
+LIB := -lm -lraylib
+
+
+synthesizer: $(APP_NAME)
+
+$(APP_NAME): $(O_FILES)
+	$(CC) $(CFLAGS) $(O_FILES) -o $(APP_NAME) $(LIB)
+
+$(BUILD)/%.o: $(SRC)/%.c
+	$(CC) $(INCLUDE) $(CFLAGS) -c $< -o $@
+
+clean:
+	rm $(BUILD)/*.o

src/main.c

@@ -0,0 +1,201 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <inttypes.h>
+#include <math.h>
+#include <raylib.h>
+#include <string.h>
+#include <stdlib.h>
+
+#define MAX_NOTES 26
+
+const int window_width = 640;
+const int window_height = 480;
+char *window_title = "synthesizer";
+
+//44100 samples per second
+const int sample_rate = 44100;
+float duration = 1.0f;
+float pcm_volume = 10000.0f;
+const float pitch_standard = 440.0; //A440
+int active_notes = 0;
+
+//convert semitone starting from pitch_standard to frequency
+float semitone(float semitone) {
+    float a = powf(2.0f, (1.0f/12.0f));
+    float n = pitch_standard * powf(a, semitone);
+    return n;
+}
+
+typedef struct note {
+	float frequency;
+	float index;
+	float step;
+	float volume;
+	bool released;
+} note;
+
+note scale[MAX_NOTES];
+
+float sine_wave(float idx) {
+	return sinf(2 * PI * idx);
+}
+
+float square_wave(float idx) {
+	if ( sine_wave(idx) > 0.0f )
+		return 0.5f;
+
+	if ( sine_wave(idx) < 0.0f )
+		return -0.5f;
+}
+
+static inline int count_active_notes(void) {
+	int active = 0;	
+	
+	for (size_t i = 0; i < MAX_NOTES; i++) {
+		if (scale[i].volume > 0.0f)
+			active++;
+	}
+	
+	return active;
+}
+
+static inline float add_notes(void) {
+	//add each notes index
+	float m = 0;
+	int active = count_active_notes();	
+
+	for (size_t i = 0; i < MAX_NOTES; i++) {
+		m += square_wave(scale[i].index) * scale[i].volume;
+	}
+
+	//don't divide by zero
+	
+	m = active ? m/active : 0.0f; //compression
+	//m = m + (1.0f - m) * 0.95f;
+	return m;
+}
+
+static inline float calc_note_step(note *n) {
+	return n->frequency/sample_rate;
+}
+
+static inline void reset_index(void) {
+	for (size_t i = 0; i < MAX_NOTES; i++) {
+
+		scale[i].index += scale[i].step;
+		if (scale[i].index > 1.0f && scale[i].volume > 0.0f) {
+			scale[i].index -= 1.0f;
+		}
+	}
+}
+
+void AudioInputCallback2(void *buffer, uint32_t frames) {
+    //audio_frequency = frequency + (audio_frequency - frequency) * 0.95f;
+	short *d = (short *)buffer;
+
+    for (size_t i = 0; i < frames; i++) {
+        d[i] = (signed short)(pcm_volume * add_notes());;
+		reset_index();
+    }
+
+}
+
+const float volume_release_step = 0.01f;
+
+void key_press(int key, note *n) {
+	if (IsKeyPressed(key)) {
+		//keys_pressed++;
+		n->released = false;
+	}
+
+	if (IsKeyReleased(key)) {
+		//keys_pressed--;
+		n->released = true;
+	}
+
+	//printf("%s\n", "wow");
+}
+
+int main(int argc, char *argv[]) {
+    InitWindow(window_width, window_height, window_title);
+    SetTargetFPS(60);
+
+    InitAudioDevice();
+    SetAudioStreamBufferSizeDefault(4096);
+
+    AudioStream stream = LoadAudioStream(44100, 16, 1);
+    SetAudioStreamCallback(stream, AudioInputCallback2);  
+
+    PlayAudioStream(stream);
+
+    const float volume_attack_step = 0.08f;
+	const float volume_release_step = 0.08f;
+	
+	//init scale
+	for (int i = 0; i < MAX_NOTES; i++) {
+		scale[i].frequency = semitone(i-24);
+		scale[i].index = 0.0f;
+		scale[i].volume = 0.0f;
+		scale[i].step = calc_note_step(&scale[i]);
+		scale[i].released = true;
+	}
+
+    while(!WindowShouldClose()) {
+		key_press(KEY_Z, &scale[0]);
+		key_press(KEY_X, &scale[1]);
+		key_press(KEY_C, &scale[2]);
+		key_press(KEY_V, &scale[3]);
+		key_press(KEY_B, &scale[4]);
+		key_press(KEY_N, &scale[5]);
+		key_press(KEY_M, &scale[6]);
+		key_press(KEY_A, &scale[7]);
+		key_press(KEY_S, &scale[8]);
+		key_press(KEY_D, &scale[9]);
+		key_press(KEY_F, &scale[10]);
+		key_press(KEY_G, &scale[11]);
+		key_press(KEY_H, &scale[12]);
+		key_press(KEY_J, &scale[13]);
+		key_press(KEY_K, &scale[14]);
+		key_press(KEY_L, &scale[15]);
+		key_press(KEY_Q, &scale[16]);
+		key_press(KEY_W, &scale[17]);
+		key_press(KEY_E, &scale[18]);
+		key_press(KEY_R, &scale[19]);
+		key_press(KEY_T, &scale[20]);
+		key_press(KEY_Y, &scale[21]);
+		key_press(KEY_U, &scale[22]);
+		key_press(KEY_I, &scale[23]);
+		key_press(KEY_O, &scale[24]);
+		key_press(KEY_P, &scale[25]);
+
+		for (int i = 0; i < MAX_NOTES; i++) {
+			if (scale[i].released) {
+				scale[i].volume -= volume_release_step;
+				if (scale[i].volume < 0.0f) {
+					scale[i].volume = 0.0f;
+					scale[i].index = 0.0f;
+				}
+			}
+		}
+
+		for (int i = 0; i < MAX_NOTES; i++) {
+			if (!scale[i].released) {
+				scale[i].volume += volume_attack_step;
+				if (scale[i].volume > 1.0f) {
+					scale[i].volume = 1.0f;
+				}
+			}
+		}
+
+
+		ClearBackground(BLACK);
+
+        BeginDrawing();
+			
+        EndDrawing();
+    }
+
+    CloseWindow();
+    return 0;
+}
+