Update pitch_table LUT to avoid divisions

This also unifies both the 44100 and variable pitch tables, reducing the
amount of space needed.

2 files changed, 30 insertions, 56 deletions

diff --git a/src/main.c b/src/main.c
index 222ffd4..cbf781d 100644
--- a/src/main.c
+++ b/src/main.c
@@ -134,10 +134,9 @@ audio_talk(Device *d, u8 b0, u8 w) {
                 c->length <<= 12; // fixed point.
                 c->data = &d->mem[mempeek16(d->dat, 0xc)];
 
-        // TODO: Volume.
-        c->vol = 12; // 0-64
-                // c->volume[0] = d->dat[0xe] >> 4;
-                // c->volume[1] = d->dat[0xe] & 0xf;
+        // Volume (Mono only for now).
+        c->vol = MAX(d->dat[0xe] >> 4, d->dat[0xe] & 0xf); // 0-64
+        c->vol *= 4 / 3;
 
                 // Looping.
                 if (!(d->dat[0xf] & 0x80)) {
@@ -150,16 +149,16 @@ audio_talk(Device *d, u8 b0, u8 w) {
                 c->pitch = d->dat[0xf] & 0x7f;
 
                 // Initialization.
+                u32 sampling_rate = length;
                 if (length > 256) {
-            c->inc = pitch_table_44100[c->pitch];
-                } else {
-            c->inc = pitch_table_variable[c->pitch] * length / AUDIO_FREQ;
+                    sampling_rate = 44100;
         }
+        c->inc = (pitch_table[c->pitch] * sampling_rate) >> 5;
 
             txt_position(0, 0);
-        txt_printf("note: %d     \n", c->pitch);
-        txt_printf("inc: %ld     \n", c->inc);
-        txt_printf("length: %ld     \n", c->length >> 12);
+        txt_printf("note:   %d     \n", c->pitch);
+        txt_printf("inc:    %ld    \n", c->inc);
+        txt_printf("length: %ld    \n", c->length >> 12);
         }
 }
 
diff --git a/src/uxn/devices/apu.c b/src/uxn/devices/apu.c
index 15eed20..4447e12 100644
--- a/src/uxn/devices/apu.c
+++ b/src/uxn/devices/apu.c
@@ -1,38 +1,22 @@
-// Calculated as (44100 << 12) / 18157 for C4
-static u32 pitch_table_44100[] = {
-    310,    329,    348,    369,    391,    414,    439,    465,
-    493,    522,    553,    586,    621,    658,    697,    739,
-    783,    829,    879,    931,    987,    1045,   1107,   1173,
-    1243,   1317,   1395,   1478,   1566,   1659,   1758,   1863,
-    1974,   2091,   2215,   2347,   2487,   2634,   2791,   2957,
-    3133,   3319,   3517,   3726,   3948,   4182,   4431,   4695,
-    4974,   5269,   5583,   5915,   6267,   6639,   7034,   7452,
-    7896,   8365,   8863,   9390,   9948,   10539,  11166,  11830,
-    12534,  13279,  14069,  14905,  15792,  16731,  17726,  18780,
-    19896,  21079,  22333,  23661,  25068,  26559,  28138,  29811,
-    31584,  33462,  35452,  37560,  39793,  42159,  44666,  47322,
-    50136,  53118,  56276,  59623,  63168,  66924,  70904,  75120,
-    79587,  84319,  89333,  94645,  100273, 106236, 112553, 119246,
-    126337, 133849, 141808, 150241, 159174, 168639, 178667, 189291,
-    200547, 212472, 225107, 238492, 252674, 267699, 283617, 300482,
-};
-
-static u32 pitch_table_variable[] = {
-    33484,    35475,    37585,    39820,    42188,    44696,    47354,    50170,
-    53153,    56314,    59663,    63210,    66969,    70951,    75170,    79640,
-    84376,    89393,    94709,    100341,   106307,   112628,   119326,   126421,
-    133939,   141903,   150341,   159281,   168752,   178787,   189418,   200682,
-    212615,   225257,   238652,   252843,   267878,   283807,   300683,   318562,
-    337505,   357574,   378837,   401364,   425230,   450515,   477305,   505687,
-    535756,   567614,   601366,   637125,   675011,   715149,   757674,   802728,
-    850460,   901031,   954610,   1011374,  1071513,  1135229,  1202733,  1274251,
-    1350022,  1430299,  1515349,  1605456,  1700921,  1802063,  1909220,  2022748,
-    2143027,  2270458,  2405466,  2548503,  2700045,  2860598,  3030698,  3210912,
-    3401843,  3604127,  3818440,  4045496,  4286054,  4540916,  4810933,  5097006,
-    5400090,  5721196,  6061396,  6421825,  6803687,  7208255,  7636880,  8090993,
-    8572108,  9081832,  9621866,  10194012, 10800180, 11442392, 12122792, 12843651,
-    13607374, 14416511, 15273761, 16181986, 17144217, 18163665, 19243733, 20388025,
-    21600360, 22884784, 24245585, 25687302, 27214749, 28833022, 30547522, 32363973,
+// Calculated as ((261.6 / 18157) << 17) for C4. If multiplied by sampling rate
+// we will have a u32 (15.17) fixed-point number. This should be enough to
+// accurately portray samples up to 75300 Hz.
+static u32 pitch_table[120] = {
+    59,    62,    66,    70,    74,    78,    83,    88,
+    93,    99,    105,   111,   118,   125,   132,   140,
+    148,   157,   166,   176,   187,   198,   210,   222,
+    236,   250,   264,   280,   297,   315,   333,   353,
+    374,   396,   420,   445,   472,   500,   529,   561,
+    594,   630,   667,   707,   749,   793,   841,   891,
+    944,   1000,  1059,  1122,  1189,  1260,  1335,  1414,
+    1498,  1587,  1682,  1782,  1888,  2000,  2119,  2245,
+    2379,  2520,  2670,  2829,  2997,  3175,  3364,  3564,
+    3776,  4001,  4239,  4491,  4758,  5041,  5341,  5658,
+    5995,  6351,  6729,  7129,  7553,  8002,  8478,  8982,
+    9517,  10083, 10682, 11317, 11990, 12703, 13459, 14259,
+    15107, 16005, 16957, 17965, 19034, 20166, 21365, 22635,
+    23981, 25407, 26918, 28519, 30215, 32011, 33915, 35931,
+    38068, 40332, 42730, 45271, 47963, 50815, 53837, 57038,
 };
 
 //
@@ -75,7 +59,7 @@ typedef struct AudioChannel {
     u32 length;
     // Length of looped portion (20.12 fixed-point, 0 to disable looping).
     u32 loop_length;
-    // TODO: this should be different?
+    // Pitch encoded as a MIDI note.
     u8 pitch;
 } AudioChannel;
 
@@ -92,15 +76,6 @@ init_sound(void) {
         channels[i] = (AudioChannel){0};
     }
 
-    // DEBUG: testing channel 0 with square wave
-    // channels[0].data = samples;
-    // channels[0].length = (LEN(samples) - 1)  << 12;
-    // channels[0].pos = 0;
-    // channels[0].inc = (44100 << 12) / AUDIO_FREQ;
-    // channels[0].vol = 32;
-    // channels[0].loop_length = channels[0].length;
-    // channels[0].loop_length = 0;
-
     // Enable the sound chip.
     SOUND_STATUS = SOUND_ENABLE;
 
@@ -111,7 +86,6 @@ init_sound(void) {
         | SOUND_DSOUND_RIGHT_A
         | SOUND_DSOUND_RESET_A;
 
-    // TODO: No pitch selection yet.
     TIMER_DATA_0 = AUDIO_TIMER;
     TIMER_CTRL_0 = TIMER_CTRL_ENABLE;
 }
@@ -135,6 +109,7 @@ void sound_vsync() {
     }
 }
 
+IWRAM_CODE
 void sound_mix() {
     // Initialize and clear mix_buffer.
     s16 mix_buffer[AUDIO_BUF_LEN];