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audio.cpp
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audio.cpp
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#include <SDL.h>
#include "math3d.h"
#include "audio.h"
std::atomic_int current_scene;
// offsets between notes on a scale
// reverse order (first offset on rightmost bit)
// i.e. 0 1 1 1 0 1 1 (plus 1 on each)
//static const uint8_t scale = 0x3B;
int8_t notesoffsets_BLUES[] = {
3, 6, 8, 9, 10, 13, 15, 18, 20, 21, 22, 25, 27, 30, 32, 33, 35,
};
int8_t notesoffsets_MIDDLE_BLUES[] = {
-5, -2, 0, 1, 2, 5, 7, 11, 12, 13, 14, 17, 19, 23, 24, 25, 27,
};
int8_t notesoffsets_DEEP_BLUES[] = {
-13, -10, -8, -7, -6, -3, -1, 3, 4, 5, 6, 9, 11, 14, 16, 17, 19,
};
//HUNGARIAN MINOR
uint16_t noteshz_HUNGARIAN[] = {
262, 294, 311, 370, 392, 415, 494, 523, 587, 622, 734, 784, 831, 988, 1047, 1175
};
#define NOTESOFFSETS notesoffsets_BLUES
const int8_t *notesoffsets = NOTESOFFSETS;
const size_t nnotesoffsets = sizeof(NOTESOFFSETS) / sizeof(*NOTESOFFSETS);
static int audio_note_duration(const audio_state *as) {
//return (int)(log1p((double)hz) * 2000 + 1000);
//return 5555;
//return 11025;
//return as->current_scene % 2 ? 5555 : 11025;
//return 22050;
return (as->note % 2 ? 8000 : 5450);
//return 11025;
//return 6666;
//return 8000;
}
static int audio_scale_duration(int scale) {
return scale == 0 ? 32 : 8;
}
static double audio_note_hz(const audio_state *as) {
int n = as->note;
int offset = n % 2 ?
notesoffsets[(as->taudigits[n / 2] % (nnotesoffsets - 1)) + 1] :
notesoffsets[0];
double hz = 220.0 * pow(2.0, (offset + as->scale) / 12.0);
return hz;
}
void audio_state_advance(audio_state *as, int samples) {
int s = as->samples + samples;
int n = as->note;
int t = as->scalenotes;
int duration = audio_note_duration(as);
while (s >= duration) {
s -= duration;
n = n + 1;
if (n % 2 && (size_t)(n / 2) >= as->ntaudigits) {
n = 0;
}
as->samples = s;
as->note = n;
duration = audio_note_duration(as);
t++;
}
duration = audio_scale_duration(as->scale);
while (t >= duration) {
t -= duration;
switch (as->scale) {
case 0:
as->scale = 7;
break;
case 7:
as->scale = 5;
break;
default:
as->scale = 0;
break;
}
duration = audio_scale_duration(as->scale);
}
as->scalenotes = t;
as->samples = s;
as->note = n;
}
static double audio_gen_note_sample_func(int samples, double hz, unsigned func) {
double t = ((int)(samples * hz) % 44100) / 44099.0;
double alpha = t * TAU;
double A = 0.0;//1.0 / pow(2, -12) - 1;//alpha / (1 + pow(2, -12));
double B = 1.3;//pow(2, -12) - 1;//alpha * (pow(2, -12));
double v = 0;
switch (func) {
case 0:
// B
// ⌠
// ⎮ sin(alpha + x) dx
// ⌡
// A
v = -sin(alpha) * cos(A) + sin(alpha) * cos(B) + cos(alpha) * sin(A) - cos(alpha) * sin(B);
break;
case 1:
v = sin(alpha);
break;
case 2:
{
// B
// ⌠
// ⎮ sin(alpha * x) / exp(|x - 1|) dx
// ⌡
// A
// calculated using sympy
double a2p1 = alpha * alpha + 1;
v = - exp(1.0) * alpha * cos(B * alpha) / (a2p1 * exp( B))
- exp(1.0) * alpha * sin(B * alpha) / (a2p1 * exp( B))
+ exp(1.0) * sin( alpha) / (a2p1 * exp(1.0))
+ exp( A) * alpha * cos(A * alpha) / (a2p1 * exp(1.0))
- exp( A) * sin(A * alpha) / (a2p1 * exp(1.0))
+ exp(1.0) * sin( alpha) / (a2p1 * exp(1.0));
v /= 2 - exp(1 - B) - exp(A - 1);
}
case 3:
if (t < 0.5) {
v = smoothstep(0, 0.5, t);
} else {
v = smoothstep(0, 0.5, 1 - t);
}
v = v * 2 - 1;
break;
default:
v = 0;
}
return v;
}
// main tones
double audio_gen_1(audio_state *as) {
double attack = 0.05;
double sustain = 0.1;
double release = 0.82;
unsigned overtones = 1;
double overtone_factor = 2;
int n = as->note;
as->note = 0;
int duration = audio_note_duration(as);
as->note = 1;
duration += audio_note_duration(as);
as->note = 0;
int s = as->samples;
if (n % 2) {
s += audio_note_duration(as);
}
as->note = n + 1 - n % 2;
double hz = audio_note_hz(as);
double u = (double)s / duration;
double v = 0;
double f = 1.0 / 4.0;
f *= smoothstep(0, attack, u);
f *= 1 - smoothstep(attack + sustain, attack + sustain + release, u);
for (unsigned i = 1; i <= overtones; i++) {
v += audio_gen_note_sample_func(s, hz * i, 2) / pow(overtone_factor, (double)i - 1);
}
v *= f;
/*
audio_state asrw = *as;
if (as->note % 2 == 0) {
asrw.scale += 4;
hz = audio_note_hz(&asrw);
v += f * audio_gen_note_sample(as->samples, hz);
asrw.scale += 3;
hz = audio_note_hz(&asrw);
v += f * audio_gen_note_sample(as->samples, hz);
} else {
v *= 3;
}
*/
//v -= 1;
//v = smoothstep(0, 0.5, 0.5 - abs(t - 0.5)) * 2 - 1;
return v;
}
// bass line
double audio_gen_2(audio_state *as) {
double attack = 0.01;
double sustain = 0.1;
double release = 0.8;
unsigned overtones = 1;
double overtone_factor = 1.5;
int s = as->samples;
int duration = audio_note_duration(as);
as->note = 0;
double hz = audio_note_hz(as);
double u = (double)s / duration;
double v = 0;
double f = 1.0 / 5.0;
f *= smoothstep(0, attack, u);
f *= 1 - smoothstep(attack + sustain, attack + sustain + release, u);
for (unsigned i = 1; i <= overtones; i++) {
v += audio_gen_note_sample_func(s, hz * i, 1) / pow(overtone_factor, (double)i - 1);
}
v *= f;
return v;
}
int16_t audio_gen(const audio_state *as) {
audio_state asrw = *as;
double v = 0;
if (as->current_scene < 16 && as->current_scene > 3) {
v += audio_gen_1(&asrw);
}
asrw = *as;
v += audio_gen_2(&asrw);
v = clamp(v, -1, 1);
return (int16_t)(v * 0x6000);
}