waveform generation, fixes of walk

.gitignore

@@ -1,3 +1,3 @@
 **/__pycache__/*
 html/
-
+**/.*/

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "tools/mmd"]
 	path = tools/mmd
 	url = https://github.com/fletcher/MultiMarkdown-6
+[submodule "tools/gifenc"]
+	path = tools/gifenc
+	url = https://github.com/lecram/gifenc

articles/oscillators/make

@@ -0,0 +1,7 @@
+#!/bin/sh
+
+cd $(dirname "$0")
+mkdir ./.dynamic
+mkdir ./.temp
+gcc waveforms.c -I../../tools ../../tools/gifenc/gifenc.c -O2 -o ./.temp/waveforms
+./.temp/waveforms

articles/oscillators/page.mmd

@@ -14,6 +14,8 @@ Inspirations are taken from [musicdsp](https://www.musicdsp.org/).
 
 ### Sine/Cosine ###
 
+![](/articles/oscillators/sine.gif)
+
 ```c
 /* Intended to be executed offline with values then embedded in the binary.
  * By having usage of glibc sin and cos functions strictly offline it's easier to have it freestanding
@@ -38,6 +40,8 @@ void pump_sinewave(struct sinewave *wave) {
 
 ### Square ###
 
+![](/articles/oscillators/sqrt.gif)
+
 ```c
 /* Implemented over sinewave */
 struct sqrtwave {
@@ -49,7 +53,9 @@ struct sqrtwave {
 } init_sqrtwave(float frequency, float phase, float amplitude) {
   struct sqrtwave r;
   r.w = init_sinewave(frequency, phase, 1.f);
-  r.v.f = amplitude;
+  v.f = r.w.s;
+  a.f = amplitude;
+  r.v.u = (a.u & 0x7fffffff) | (v.u & 0x80000000);
   return r;
 }
 
@@ -68,6 +74,8 @@ void pump_sqrtwave(struct sqrtwave *wave) {
 
 ### Saw ###
 
+![](/articles/oscillators/sawt.gif)
+
 ```c
 struct sawtwave {
   float v, a, i;
@@ -75,7 +83,7 @@ struct sawtwave {
   struct sawtwave r;
   r.v = sinf(phase) * amplitude;
   r.a = amplitude;
-  r.i = frequency / AUDIO_FRAME_RATE * amplitude;
+  r.i = 2.f * frequency / AUDIO_FRAME_RATE * amplitude;
   return r;
 }
 
@@ -83,7 +91,11 @@ struct sawtwave {
 void pump_sawtwave(struct sawtwave *wave) {
   wave->v += wave->i;
   if (wave->v > wave->a)
-    wave->v -= wave->a;
+    wave->v -= wave->a * 2.f;
 }
 
 ```
+
+### Edits ###
+- Fixed initial value based on phase in sqrtwave, proper range for sawtwave.
+- Added waveform gifs.

articles/oscillators/waveforms.c

@@ -0,0 +1,138 @@
+#include <stdio.h>
+#include <inttypes.h>
+#include <math.h>
+#include <assert.h>
+#include <string.h>
+
+#include "gifenc/gifenc.h"
+
+#define NOTE 440
+#define AUDIO_FRAME_RATE 44100
+#define LENGTH (AUDIO_FRAME_RATE / NOTE)
+
+#define WIDTH LENGTH * 4
+#define HEIGHT 128
+
+#define RED 0
+#define GREEN 0
+#define BLUE 0
+
+static struct sinewave {
+    float f, s, c;
+} init_sinewave(float frequency, float phase, float amplitude) {
+    struct sinewave r;
+    r.f = 2.f * sinf((float)M_PI * frequency / (float)AUDIO_FRAME_RATE);
+    r.s = amplitude * sinf(phase);
+    r.c = amplitude * cosf(phase);
+    return r;
+}
+
+static float pump_sinewave(struct sinewave *wave) {
+    wave->s -= wave->f * wave->c;
+    wave->c += wave->f * wave->s;
+    return wave->s;
+}
+
+static struct sqrtwave {
+  struct sinewave w;
+  union {
+    float f;
+    uint32_t u;
+  } v;
+} init_sqrtwave(float frequency, float phase, float amplitude) {
+    struct sqrtwave r;
+  union {
+    float f;
+    uint32_t u;
+  } v, a;
+    r.w = init_sinewave(frequency, phase, 1.f);
+    v.f = r.w.s;
+    a.f = amplitude;
+    r.v.u = (a.u & 0x7fffffff) | (v.u & 0x80000000);
+    return r;
+}
+
+static float pump_sqrtwave(struct sqrtwave *wave) {
+  union {
+    float f;
+    uint32_t u;
+  } v;
+    pump_sinewave(&wave->w);
+    v.f = wave->w.s;
+    wave->v.u = (wave->v.u & 0x7fffffff) | (v.u & 0x80000000);
+    return wave->v.f;
+}
+
+static struct sawtwave {
+    float v, a, i;
+} init_sawtwave(float frequency, float phase, float amplitude) {
+    struct sawtwave r;
+    r.v = sinf(phase) * amplitude;
+    r.a = amplitude;
+    r.i = 2.f * frequency / AUDIO_FRAME_RATE * amplitude;
+    return r;
+}
+
+static float pump_sawtwave(struct sawtwave *wave) {
+    wave->v += wave->i;
+    if (wave->v > wave->a)
+      wave->v -= wave->a * 2.f;
+    return wave->v;
+}
+
+static int absi(int v) {
+    return v > 0 ? v : -v;
+}
+
+static void plot_line(uint8_t *frame, int x, int xt, int y, int yt) {
+    int dx = xt - x;
+    int dy = yt - y;
+    int step = absi(dx) >= absi(dy) ? absi(dx) : absi(dy);
+    dx /= step;
+    dy /= step;
+    int xc = x;
+    int yc = y;
+    int i = 1;
+    while (i <= step) {
+        frame[xc + yc * WIDTH] = 1;
+        xc += dx;
+        yc += dy;
+        i++;
+    }
+}
+
+static void generate_wave(char const *filepath, void *generator, float (*pumper)(void *)) {
+  float wave[LENGTH];
+  for (int i = 0; i < LENGTH; ++i) {
+    wave[i] = pumper(generator);
+  }
+  uint8_t palette[6] = { [3] = RED, [4] = GREEN, [5] = BLUE };
+  ge_GIF *g = ge_new_gif(filepath, WIDTH, HEIGHT, palette, 1, 0, 0);
+  assert(g);
+  for (int f = 0; f < LENGTH; ++f) {
+    memset(g->frame, 0, WIDTH * HEIGHT);
+    for (int i = 0; i < WIDTH; ++i) {
+        int l0 = (int)((wave[(f + i) % LENGTH] + 1.0f) * 127.5f) / 2;
+        int l1 = (int)((wave[(f + i + 1) % LENGTH] + 1.0f) * 127.5f) / 2;
+        if (i == WIDTH - 1)
+            g->frame[i + l0 * WIDTH] = 1;
+        else
+            plot_line(g->frame, i, i + 1, l0, l1);
+    }
+    ge_add_frame(g, 1);
+  }
+  ge_close_gif(g);
+}
+
+int main(void) {
+    struct sinewave sine = init_sinewave((float)NOTE, 0.0f, 1.0f);
+    generate_wave(".dynamic/sine.gif", &sine, pump_sinewave);
+
+    struct sqrtwave sqrt = init_sqrtwave((float)NOTE, 0.0f, 1.0f);
+    generate_wave(".dynamic/sqrt.gif", &sqrt, pump_sqrtwave);
+
+    struct sawtwave sawt = init_sawtwave((float)NOTE, 0.0f, 1.0f);
+    generate_wave(".dynamic/sawt.gif", &sawt, pump_sawtwave);
+
+    return 0;
+}

compile.sh

@@ -6,8 +6,15 @@ mkdir -p ./html/articles
 
 ./tools/main_page_generator.py ./articles | ./tools/mmd/build/multimarkdown > ./html/index.html
 
-for d in ./articles/*; do
+for d in ./articles/*/; do
   if [ -d "$d" ]; then
+    if test -f "$d/make"; then
+      "$d/make"
+    fi
+    if test -d "$d/.dynamic"; then
+      mkdir -p "./html/articles/$(basename -- $d)"
+      cp -r "$d/.dynamic/." "./html/articles/$(basename -- $d)/"
+    fi
     ./tools/article_wrapper.py "$d/page.mmd" | ./tools/mmd/build/multimarkdown > "./html/articles/$(basename -- $d).html"
   fi
 done

tools/feed_generator.py

@@ -57,6 +57,7 @@ for root, dirs, _ in walk(argv[1]):
             f"""        <link>{address}/articles/{urllib.parse.quote(d)}</link>\n"""
             "    </item>\n"
         )
+    break
 
 feed += """    </channel>
 </rss>"""

tools/gifenc

@@ -0,0 +1 @@
+Subproject commit 87acd487dfa2f2a638eec751a1d6c2fff60822da

tools/main_page_generator.py

@@ -38,6 +38,7 @@ for root, dirs, _ in walk(argv[1]):
         )
         if "Tags" in metadata:
             page += f""">*{','.join(metadata["Tags"])}*\n---\n"""
+    break
 
 curtime = time.gmtime(int(time.time()))
 page += f"Last compiled: *{MONTHS[curtime.tm_mon]} {curtime.tm_mday}, {curtime.tm_year} {curtime.tm_hour}:{curtime.tm_min:02d} UTC*\n\n"

tools/track_listing_generator.py

@@ -88,6 +88,7 @@ for _, _, files in walk(argv[1]):
             f"""        <div><p style="display: inline;">{f[:-4]}</p><button style="float: right;" onclick="window.loadAndPlayTrack('/tracks/{f}')">play</button></div>\n"""
                "        <hr/>\n"
         )
+    break
 
 page += """    </div>
 </div>