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Add fft

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This commit is contained in:
Markus Järvisalo
2025-07-14 22:52:15 +03:00
parent f1343ea200
commit 96de65cde0
9 changed files with 174 additions and 25 deletions
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74
src/fft.cpp Normal file
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@ -0,0 +1,74 @@
#include "fft.h"
#include <math.h>
static float window[FFT_SIZE];
// Call once before use
void init_hamming_window() {
for (int i = 0; i < FFT_SIZE; i++) {
window[i] = 0.54f - 0.46f * cosf(2.0f * (float)M_PI * i / (FFT_SIZE - 1));
}
}
static unsigned int bit_reverse(unsigned int x, int log2n) {
unsigned int n = 0;
for (int i = 0; i < log2n; i++) {
n <<= 1;
n |= (x & 1);
x >>= 1;
}
return n;
}
void compute_fft(float* time_data, float* freq_out) {
static float real[FFT_SIZE];
static float imag[FFT_SIZE];
int log2n = 0;
for (int t = FFT_SIZE; t > 1; t >>= 1) ++log2n;
// Apply Hamming window
for (int i = 0; i < FFT_SIZE; i++) {
real[i] = time_data[i] * window[i];
imag[i] = 0.0f;
}
// Bit reversal
for (int i = 0; i < FFT_SIZE; ++i) {
int j = bit_reverse(i, log2n);
if (j > i) {
float tmp_re = real[i], tmp_im = imag[i];
real[i] = real[j]; imag[i] = imag[j];
real[j] = tmp_re; imag[j] = tmp_im;
}
}
// Cooley-Tukey FFT
for (int s = 1; s <= log2n; ++s) {
int m = 1 << s;
for (int k = 0; k < FFT_SIZE; k += m) {
for (int j = 0; j < m / 2; ++j) {
int t = k + j;
int u = t + m / 2;
float angle = -2.0f * (float)M_PI * j / m;
float w_real = cosf(angle);
float w_imag = sinf(angle);
float re = w_real * real[u] - w_imag * imag[u];
float im = w_real * imag[u] + w_imag * real[u];
real[u] = real[t] - re;
imag[u] = imag[t] - im;
real[t] += re;
imag[t] += im;
}
}
}
for (int i = 0; i < FFT_SIZE / 2; ++i) {
float mag = sqrtf(real[i] * real[i] + imag[i] * imag[i]) / FFT_SIZE;
freq_out[i] = mag;
}
}

12
src/fft.h Normal file
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@ -0,0 +1,12 @@
#pragma once
#include <stdlib.h>
#include <math.h>
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
#define FFT_SIZE 4096
void init_hamming_window();
void compute_fft(float* time_data, float* freq_out);

58
src/main.cpp
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@ -1,6 +1,6 @@
// custom build and feature flags
#ifdef DEBUG
#define OPENGL_DEBUG 1
#define OPENGL_DEBUG 0
#define FULLSCREEN 0
#define DESPERATE 0
#define BREAK_COMPATIBILITY 0
@ -29,6 +29,7 @@
#include "shaders/post.inl"
#endif
#include "fft.h"
#pragma data_seg(".pids")
// static allocation saves a few bytes
@ -74,13 +75,13 @@ int __cdecl main(int argc, char* argv[])
#if POST_PASS
pidPost = ((PFNGLCREATESHADERPROGRAMVPROC)wglGetProcAddress("glCreateShaderProgramv"))(GL_FRAGMENT_SHADER, 1, &post_frag);
#endif
#ifdef SU_LOAD_GMDLS
su_load_gmdls();
#endif // SU_LOAD_GMDLS
// initialize sound
#ifndef EDITOR_CONTROLS
#if USE_AUDIO
LPDIRECTSOUND direct_sound;
LPDIRECTSOUNDBUFFER direct_sound_buffer;
DirectSoundCreate(0, &direct_sound, 0);
@ -91,6 +92,7 @@ int __cdecl main(int argc, char* argv[])
LPVOID p1;
DWORD l1;
IDirectSoundBuffer_Lock(direct_sound_buffer, 0, SU_LENGTH_IN_SAMPLES * SU_CHANNEL_COUNT * SU_SAMPLE_SIZE, &p1, &l1, NULL, NULL, 0);
CreateThread(0, 0, (LPTHREAD_START_ROUTINE)su_render_song, p1, 0, 0);
#endif
@ -108,13 +110,26 @@ int __cdecl main(int argc, char* argv[])
long playCursor = 0;
long lastPlayCursor = -1;
// main loop
volatile float maximum = 0.0; // Helper variable to calculate maximum fft output for normalization
// Unlock buffer for next use
IDirectSoundBuffer_Unlock(direct_sound_buffer, p1, SU_LENGTH_IN_SAMPLES * SU_CHANNEL_COUNT * SU_SAMPLE_SIZE, NULL, NULL);
// Play sound
direct_sound_buffer->Play(0, 0, 0);
static float syncs[1 + SU_NUMSYNCS];
// Init FFT
init_hamming_window();
// FFT buffers
static float fft_input[FFT_SIZE];
static float fft_output[FFT_SIZE / 2]; // Magnitudes
static float fft_uniform[FFT_SIZE / 4];
do
{
direct_sound_buffer->GetCurrentPosition((DWORD*)&playCursor, NULL);
float syncs[1 + SU_NUMSYNCS];
#if !(DESPERATE)
// do minimal message handling so windows doesn't kill your application
@ -144,7 +159,39 @@ int __cdecl main(int argc, char* argv[])
#endif
syncs[0] = (float)playCursor / (2 * sizeof(SUsample));
/******************
* FFT
*******************/
LPVOID audio_ptr = NULL;
DWORD audio_size = 0;
// Read audio
HRESULT hr = IDirectSoundBuffer_Lock(direct_sound_buffer, 0, FFT_SIZE * sizeof(SUsample), &audio_ptr, &audio_size, NULL, NULL, DSBLOCK_FROMWRITECURSOR);
if (SUCCEEDED(hr) && audio_ptr) {
SUsample* samples = (SUsample*)audio_ptr;
for (int i = 0; i < FFT_SIZE; ++i) {
fft_input[i] = (float)samples[i];
}
IDirectSoundBuffer_Unlock(direct_sound_buffer, audio_ptr, audio_size, NULL, 0);
}
// Calculate FFT
compute_fft(fft_input, fft_output);
// Normalize output
for (int i = 0; i < (FFT_SIZE / 2); i++)
{
maximum = max(fft_output[i], maximum);
fft_output[i] = fft_output[i] / maximum;
if (i < (FFT_SIZE / 4)) // Limit uniform fft size. High frequencys contain nothing interesing.
{
fft_uniform[i] = fft_output[i];
}
}
syncs[0] = (float)playCursor / (2 * sizeof(SUsample));
for (int i = 0; i < SU_NUMSYNCS; ++i)
{
@ -153,6 +200,7 @@ int __cdecl main(int argc, char* argv[])
PFNGLUNIFORM1FVPROC glUniform1fvProc = ((PFNGLUNIFORM1FVPROC)wglGetProcAddress("glUniform1fv"));
glUniform1fvProc(0, SU_NUMSYNCS + 1, syncs);
glUniform1fvProc(8, FFT_SIZE / 4, fft_uniform);
glRects(-1, -1, 1, 1);

16
src/shaders/fragment.frag
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@ -3,6 +3,7 @@ precision mediump float;
out vec4 o;
const float PI = 22./7.;
layout(location = 0) uniform float syncs[7];
layout(location = 8) uniform float fft_output[512]; // FFT_SIZE / 4
float u_time = syncs[0];
vec3 render(vec2 uv, float time) {
@ -23,5 +24,18 @@ vec3 render(vec2 uv, float time) {
void main() {
vec2 uv = gl_FragCoord.xy * 2. / vec2(1920,1080);
vec3 col = render(uv, u_time);
o = vec4(col,1.0);
// Determine FFT bin index for current x position
int index = int(floor(uv.x*128.0));
index = clamp(index, 0, 255);
// Get the FFT energy (clamped to avoid NaNs or overflow)
float energy = clamp(fft_output[index], .0, 1.0);
float bar_height = energy;
float fade = smoothstep(bar_height, bar_height + 0.02, 1.0 - uv.y);
vec3 color = vec3(fade);
o = vec4(color, 1.0);
}

14
src/shaders/fragment.inl
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@ -1,6 +1,7 @@
// Generated with Shader Minifier 1.5.1 (https://github.com/laurentlb/Shader_Minifier/)
#ifndef FRAGMENT_INL_
# define FRAGMENT_INL_
# define VAR_fft_output "l"
# define VAR_o "f"
# define VAR_syncs "v"
@ -10,20 +11,13 @@ const char *fragment_frag =
"out vec4 f;"
"const float m=22./7.;"
"layout(location=0)uniform float v[7];"
"layout(location=8)uniform float l[512];"
"float n=v[0];"
"vec3 s(vec2 f)"
"{"
"float m=v[4];"
"return f.x>=m&&f.x<=m+.01?"
"vec3(1):"
"f.x>=0.&&f.x<=.01?"
"vec3(abs(v[3]*2)):"
"vec3(.1,.2,.3)*abs(v[1]*1.2);"
"}"
"void main()"
"{"
"vec2 m=gl_FragCoord.xy*2./vec2(1920,1080);"
"f=vec4(s(m),1);"
"float n=clamp(l[clamp(int(floor(m.x*128.)),0,255)],0.,1.);"
"f=vec4(vec3(smoothstep(n,n+.02,1.-m.y)),1);"
"}";
#endif // FRAGMENT_INL_

4
src/sointu/song.h
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@ -3,14 +3,14 @@
#define SU_RENDER_H
#define SU_CHANNEL_COUNT 2
#define SU_LENGTH_IN_SAMPLES 920256
#define SU_LENGTH_IN_SAMPLES 8282304
#define SU_BUFFER_LENGTH (SU_LENGTH_IN_SAMPLES*SU_CHANNEL_COUNT)
#define SU_SAMPLE_RATE 44100
#define SU_BPM 138
#define SU_ROWS_PER_BEAT 4
#define SU_ROWS_PER_PATTERN 16
#define SU_LENGTH_IN_PATTERNS 12
#define SU_LENGTH_IN_PATTERNS 108
#define SU_LENGTH_IN_ROWS (SU_LENGTH_IN_PATTERNS*SU_PATTERN_SIZE)
#define SU_SAMPLES_PER_ROW (SU_SAMPLE_RATE*60/(SU_BPM*SU_ROWS_PER_BEAT))
#define SU_NUMSYNCS 4