Initial commit

Makefile

@@ -0,0 +1,15 @@
+CC=cc
+CFLAGS=-Wall -Wextra -O3 # -ggdb
+LIBS=-lraylib -lm
+
+all: fft gen
+
+fft: main.c
+	$(CC) $(CFLAGS) -o fft main.c $(LIBS)
+
+gen: gen.c
+	$(CC) $(CFLAGS) -o gen gen.c $(LIBS)
+
+clean:
+	rm -rf fft
+	rm -rf gen

gen.c

@@ -0,0 +1,25 @@
+#include <math.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#define SAMPLE_RATE 44100
+#define DURATION 5
+#define FREQUENCY 440
+#define VOLUME 0.3f
+
+int main() {
+    for (size_t i = 0; i < DURATION * SAMPLE_RATE; ++i) {
+        float t = (float)i / SAMPLE_RATE;
+        float volume = (float)INT16_MAX * VOLUME;
+        int16_t sample = 0;
+
+        sample = (int16_t)
+        (
+            (sinf(2*M_PI *   FREQUENCY * t) * volume) +
+            (sinf(2*M_PI * 2*FREQUENCY * t) * volume)
+        );
+        fwrite(&sample, sizeof(sample), 1, stdout);
+    }
+
+    return 0;
+}

gen.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+
+set -xe
+
+make gen && ./gen | ffmpeg -f s16le -i pipe: -y output.mp3

main.c

@@ -0,0 +1,266 @@
+#include <assert.h>
+#include <complex.h>
+#include <math.h>
+#include <raylib.h>
+#include <raymath.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define STEP 1.06f
+#define LOWF 1.0f
+#define LERP 0.4f
+
+typedef struct {
+    float left;
+    float right;
+} Frame;
+
+#define N (1<<13)
+Frame g_frames[N];
+size_t g_frames_count = 0;
+
+float g_in[N];
+float complex g_out1[N];
+float complex g_out2[N];
+float complex *g_out_front = g_out1;
+float complex *g_out_back = g_out2;
+
+void dft(float in[], float complex out[], size_t n)
+{
+    for (size_t f = 0; f < n; ++f) {
+        out[f] = 0.0f;
+        for (size_t i = 0; i < n; ++i) {
+            float t = (float)i / n;
+            out[f] += in[i] * cexpf(2*I*M_PI*f*t);
+        }
+    }
+}
+
+void fft(float in[], size_t stride, float complex out[], size_t n)
+{
+    assert(n > 0);
+
+    if (n == 1) {
+        out[0] = in[0];
+        return;
+    }
+
+    fft(in, stride*2, out, n/2);
+    fft(in + stride, stride*2, out + n/2, n/2);
+
+    for (size_t k = 0; k < n/2; ++k) {
+        float t = (float)k/n;
+        float complex v = cexpf(-2*I*M_PI*t) * out[k + n/2];
+        float complex e = out[k];
+        out[k] = e + v;
+        out[k + n/2] = e - v;
+    }
+}
+
+void callback(void *buffer_data, unsigned int frames)
+{
+    if (frames <= N - g_frames_count) {
+        memcpy(g_frames + g_frames_count, buffer_data, sizeof(Frame) * frames);
+        g_frames_count += frames;
+    } else if (frames <= N) {
+        memmove(g_frames, g_frames + frames, sizeof(Frame) * (N - frames));
+        memcpy(g_frames + (N - frames), buffer_data, sizeof(Frame) * frames);
+    } else {
+        memcpy(g_frames, buffer_data, sizeof(Frame) * N);
+        g_frames_count = N;
+    }
+}
+
+void render_wave(void)
+{
+    float w = GetScreenWidth();
+    float h = GetScreenHeight();
+    float cell_width = (float)w/g_frames_count;
+    Color color = {50, 50, 50, 20};
+#if 1
+    for (size_t i = 0; i < N; ++i) {
+        float sample = fabsf(g_frames[i].left);
+        // if (sample > 0.0f) {
+        //     DrawRectangle(i*cell_width, h/2 - h/2*sample, 1, h/2*sample, color);
+        // } else {
+        //     DrawRectangle(i*cell_width, h/2, 1, h/2*-sample, color);
+        // }
+        float height = h/2*sample/2;
+        // color.a = 40 + 128*sample;
+        color.r = 50*sample;
+        color.g = 64 - color.r;
+        color.b = 64 - color.r;
+        DrawRectangle(i*cell_width, h/2 - height, 1, 2*height, color);
+    }
+#else
+    size_t to = g_frames_count == 0 ? 1 : g_frames_count;
+    for (size_t i = 0; i < to - 1; ++i) {
+        float t1 = (float)i/g_frames_count;
+        float t2 = (float)(i+1)/g_frames_count;
+        // float hann1 = 0.5f - 0.5f * cosf(2*M_PI*t1);
+        // float hann2 = 0.5f - 0.5f * cosf(2*M_PI*t2);
+        float sample1 = g_frames[i].left/3/* * hann1*/;
+        float sample2 = g_frames[i+1].left/3/* * hann2*/;
+        DrawLine(i*cell_width, h/2 + h/2*sample1, (i+1)*cell_width, h/2 + h/2*sample2,
+                 color);
+    }
+#endif
+}
+
+float amp(float complex z)
+{
+    float a = crealf(z);
+    float b = cimagf(z);
+    return logf(a*a + b*b);
+}
+
+float complex clerp(float complex start, float complex end, float amount)
+{
+    float complex result = start + amount*(end - start);
+    return result;
+}
+
+float g_max_amp = 0.0f;
+void render_fft(void)
+{
+    float w = GetScreenWidth();
+    float h = GetScreenHeight();
+
+    for (size_t i = 0; i < g_frames_count; ++i) {
+        float t = (float)i/g_frames_count;
+        float hann = 0.5f - 0.5f * cosf(2*M_PI*t);
+        g_in[i] = g_frames[i].left * hann;
+    }
+
+    float complex *tmp = g_out_back;
+    g_out_back = g_out_front;
+    g_out_front = tmp;
+
+    fft(g_in, 1, g_out_back, N);
+
+    for (size_t i = 0; i < N; ++i) {
+        float a = amp(g_out_back[i]);
+        if (a > g_max_amp) {
+            g_max_amp = a;
+        }
+
+        g_out_back[i] = clerp(g_out_front[i], g_out_back[i], LERP);
+    }
+
+    float step = STEP;
+    float lowf = LOWF;
+    size_t m = 0;
+    for (float f = lowf; (size_t)f < N/2; f = ceilf(f*step)) {
+        m += 1;
+    }
+
+    float cell_width = (float)w/m;
+    float prev_t = 0.0f;
+    m = 0;
+    for (float f = lowf; (size_t)f < N/2; f = ceilf(f*step)) {
+        float f1 = ceilf(f*step);
+        float a = 0.0f;
+        for (size_t q = (size_t)f; q < N/2 && q < (size_t)f1; ++q) {
+            float b = amp(g_out_back[q]);
+            if (b > a) {
+                a = b;
+            }
+        }
+        float t = a/g_max_amp;
+        float tf = f / N/2;
+        Color c = {255*t, 255*tf, 255*m, 255*t};
+        // DrawRectangle(m*cell_width, h - h/2*t, cell_width, h/2*t, c);
+        // RLAPI void DrawRectangle(int posX, int posY, int width, int height, Color color);
+        // RLAPI void DrawLine(int startPosX, int startPosY, int endPosX, int endPosY, Color color);
+        float x1 = m*cell_width;
+        float y1 = h - h/2*prev_t;
+        float x2 = x1 + cell_width;
+        float y2 = h - h/2*t;
+        // DrawLine(x1, y1, x2, y2, c);
+        Vector2 v1 = {x1, h};
+        Vector2 v2 = {x2, h};
+        Vector2 v3 = {x1, y1};
+        Vector2 v4 = {x2, y2};
+        DrawTriangle(v1, v2, v4, c);
+        DrawTriangle(v4, v3, v1, c);
+        prev_t = t;
+        m += 1;
+    }
+}
+
+int main(int argc, char **argv)
+{
+    if (argc <= 1) {
+        fprintf(stderr, "ERROR: Incorrect usage\n");
+        return EXIT_FAILURE;
+    }
+
+    SetConfigFlags(FLAG_WINDOW_RESIZABLE);
+    InitWindow(800, 600, "Fast Fourier Transform");
+    SetTargetFPS(60);
+    InitAudioDevice();
+
+    Music music = LoadMusicStream(argv[1]);
+    printf("music.frameCount = %u\n", music.frameCount);
+    printf("music.stream.sampleRate = %u\n", music.stream.sampleRate);
+    printf("music.stream.sampleSize = %u\n", music.stream.sampleSize);
+    printf("music.stream.channels = %u\n", music.stream.channels);
+
+    AttachAudioStreamProcessor(music.stream, callback);
+    SetMusicVolume(music, 0.5);
+    PlayMusicStream(music);
+
+    bool toggle_wave = true;
+    bool toggle_fft = true;
+    float pitch = 1.0f;
+
+    while (!WindowShouldClose()) {
+        UpdateMusicStream(music);
+
+        if (IsKeyPressed(KEY_SPACE)) {
+            if (IsMusicStreamPlaying(music)) {
+                PauseMusicStream(music);
+            } else {
+                ResumeMusicStream(music);
+            }
+        }
+        if (IsKeyPressed(KEY_UP)) {
+            pitch += 0.05f;
+            SetMusicPitch(music, pitch);
+        }
+        if (IsKeyPressed(KEY_DOWN)) {
+            pitch -= 0.05f;
+            SetMusicPitch(music, pitch);
+        }
+        if (IsKeyPressed(KEY_LEFT)) {
+            SeekMusicStream(music, GetMusicTimePlayed(music) - 10.0f);
+        }
+        if (IsKeyPressed(KEY_RIGHT)) {
+            SeekMusicStream(music, GetMusicTimePlayed(music) + 10.0f);
+        }
+        if (IsKeyPressed(KEY_W)) {
+            toggle_wave = !toggle_wave;
+        }
+        if (IsKeyPressed(KEY_F)) {
+            toggle_fft = !toggle_fft;
+        }
+
+        BeginDrawing();
+        ClearBackground(BLACK);
+        if (toggle_wave) {
+            render_wave();
+        }
+        if (toggle_fft) {
+            render_fft();
+        }
+        EndDrawing();
+    }
+
+    CloseAudioDevice();
+    CloseWindow();
+
+    return EXIT_SUCCESS;
+}