From 434b8be1518a4e706c1a88d934cae54e0b8540dd Mon Sep 17 00:00:00 2001
From: John Alanbrook <john@pockle.world>
Date: Mon, 4 Jul 2022 19:19:52 +0000
Subject: [PATCH] DSP

---
 source/engine/dsp.c   | 87 +++++++++++++++++++++++++++++++++++++++++++
 source/engine/dsp.h   | 12 ++++++
 source/engine/sound.c |  9 +++--
 3 files changed, 105 insertions(+), 3 deletions(-)
 create mode 100644 source/engine/dsp.c
 create mode 100644 source/engine/dsp.h

diff --git a/source/engine/dsp.c b/source/engine/dsp.c
new file mode 100644
index 0000000..30d832a
--- /dev/null
+++ b/source/engine/dsp.c
@@ -0,0 +1,87 @@
+#include "dsp.h"
+
+#include "sound.h"
+#include "limits.h"
+#include "math.h"
+
+#define PI 3.14159265
+
+void am_mod(short *a, short *b, short *c, int n)
+{
+    for (int i = 0; i < n; i++) {
+        c[i] = (a[i]*b[i])>>15;
+    }
+}
+
+static struct wav make_wav(float freq, int sr, int ch) {
+    struct wav new;
+    new.ch = ch;
+    new.samplerate = sr;
+    new.frames = sr/freq;
+    new.data = calloc(new.frames*new.ch, sizeof(short));
+
+    return new;
+}
+
+struct wav gen_sine(float amp, float freq, int sr, int ch)
+{
+    struct wav new = make_wav(freq, sr, ch);
+
+    if (amp > 1) amp = 1;
+    if (amp < 0) amp = 0;
+    short samp = amp*SHRT_MAX;
+
+    short *data = (short*)new.data;
+
+    for (int i = 0; i < new.frames; i++) {
+        for (int j = 0; j < new.ch; j++) {
+            data[i+j] =amp * sin(2*PI*((float)i / new.frames));
+        }
+    }
+
+    return new;
+}
+
+struct wav gen_square(float amp, float freq, int sr, int ch)
+{
+    struct wav new = make_wav(freq, sr, ch);
+
+    int crossover = new.frames/2;
+
+    if (amp > 1) amp = 1;
+    if (amp < 0) amp = 0;
+
+    short samp = amp * SHRT_MAX;
+
+    short *data = (short*)new.data;
+
+    for (int i = 0; i < crossover; i++) {
+        for (int j = 0; j < new.ch; j++) {
+            data[i+j] = samp;
+        }
+    }
+
+    for (int i = crossover; i < new.frames; i++) {
+        for (int j = 0; j < new.ch; j++) {
+            data[i+j] = samp * -1;
+        }
+    }
+
+    return new;
+}
+
+struct wav gen_triangle(float amp, float freq, int sr, int ch)
+{
+    struct wav new = make_wav(freq, sr, ch);
+
+    if (amp > 1) amp = 1;
+    if (amp < 0) amp = 0;
+
+
+
+    for (int i = 0; i < new.frames; i++) {
+        for (int j = 0; j < new.ch; j++) {
+            //new.data[i+j] =
+        }
+    }
+}
\ No newline at end of file
diff --git a/source/engine/dsp.h b/source/engine/dsp.h
new file mode 100644
index 0000000..41c1be6
--- /dev/null
+++ b/source/engine/dsp.h
@@ -0,0 +1,12 @@
+#ifndef DSP_H
+#define DSP_H
+
+void am_mod(short *a, short *b, short *c, int n);
+
+struct wav;
+
+struct wav gen_sine(float amp, float freq, int sr, int ch);
+struct wav gen_square(float amp, float freq, int sr, int ch);
+struct wav gen_triangle(float amp, float freq, int sr, int ch);
+
+#endif
\ No newline at end of file
diff --git a/source/engine/sound.c b/source/engine/sound.c
index 6da07f2..226ac90 100755
--- a/source/engine/sound.c
+++ b/source/engine/sound.c
@@ -7,6 +7,8 @@
 #include "limits.h"
 #include "time.h"
 
+#include "dsp.h"
+
 
 #define DR_WAV_IMPLEMENTATION
 #include "dr_wav.h"
@@ -133,15 +135,16 @@ void sound_init()
 
     printf("Loaded wav: ch %i, sr %i, fr %i.\n", mwav.ch, mwav.samplerate, mwav.frames);
 
+    mwav = gen_square(1, 150, 48000, 2);
+
+/*
     short *tdata = mwav.data;
     mwav.frames /= 2;
     short *newdata = calloc(mwav.frames * 2, sizeof(short));
     for (int i = 0; i < mwav.frames; i++) {
         newdata[i] = tdata[i*2];
     }
-
-    free(mwav.data);
-    mwav.data = newdata;
+*/
 
     wavsound.data = &mwav;
     wavsound.loop = 1;