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created note LUT for MIDI notes

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Annika
2026-07-27 00:19:06 -07:00
parent 66bea462e7
commit accc98c357
2 changed files with 32 additions and 38 deletions
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oscillator.cpp
+19 -38
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@@ -4,25 +4,23 @@ namespace Fem {
class Oscillator { class Oscillator {
private: private:
// 11.21 fixed point amount to increment per 48kHz clock cycle const uint32_t NOTELUT[128] = {
// 11.8 used, least significant 13 bits only used for accumulator precision 0x000b29a6, 0x000bd392, 0x000c879a, 0x000d4656, 0x000e1069, 0x000ee680, 0x000fc953, 0x0010b9a2,
const uint32_t NOTELUT[16] = { 0x0011b83c, 0x0012c5f9, 0x0013e3c0, 0x00151285, 0x0016534c, 0x0017a725, 0x00190f34, 0x001a8cac,
749114669, // C9 0x001c20d2, 0x001dcd01, 0x001f92a6, 0x00217345, 0x00237078, 0x00258bf2, 0x0027c780, 0x002a250b,
793659848, // C#9 0x002ca698, 0x002f4e4b, 0x00321e68, 0x00351958, 0x003841a5, 0x003b9a03, 0x003f254d, 0x0042e68a,
840853486, // D9 0x0046e0f0, 0x004b17e4, 0x004f8f01, 0x00544a17, 0x00594d30, 0x005e9c96, 0x00643cd1, 0x006a32b0,
890853486, // D#9 0x0070834b, 0x00773407, 0x007e4a9b, 0x0085cd15, 0x008dc1e0, 0x00962fc9, 0x009f1e02, 0x00a8942e,
943826222, // E9 0x00b29a61, 0x00bd392c, 0x00c879a3, 0x00d46561, 0x00e10697, 0x00ee680e, 0x00fc9536, 0x010b9a2a,
999948917, // F9 0x011b83c1, 0x012c5f92, 0x013e3c05, 0x0151285c, 0x016534c3, 0x017a7259, 0x0190f346, 0x01a8cac3,
1059409160, // F#9 0x01c20d2e, 0x01dcd01d, 0x01f92a6c, 0x02173455, 0x02370783, 0x0258bf25, 0x027c780b, 0x02a250b9,
1122404698, // G9 0x02ca6986, 0x02f4e4b3, 0x0321e68d, 0x03519586, 0x03841a5d, 0x03b9a03a, 0x03f254d9, 0x042e68ab,
1189146700, // G#9D 0x046e0f06, 0x04b17e4b, 0x04f8f016, 0x0544a173, 0x0594d30d, 0x05e9c967, 0x0643cd1a, 0x06a32b0c,
1259857073, // A9 0x070834ba, 0x07734074, 0x07e4a9b2, 0x085cd157, 0x08dc1e0d, 0x0962fc96, 0x09f1e02d, 0x0a8942e6,
1334772041, // A#9 0x0b29a61a, 0x0bd392cf, 0x0c879a35, 0x0d465619, 0x0e106974, 0x0ee680e9, 0x0fc95364, 0x10b9a2ae,
1414141247, // B9 0x11b83c1a, 0x12c5f92c, 0x13e3c05a, 0x151285cd, 0x16534c34, 0x17a7259f, 0x190f346a, 0x1a8cac33,
0, // invalid 0x1c20d2e8, 0x1dcd01d2, 0x1f92a6c8, 0x2173455d, 0x23707834, 0x258bf258, 0x27c780b4, 0x2a250b9b,
0, // invalid 0x2ca69869, 0x2f4e4b3f, 0x321e68d4, 0x35195867, 0x3841a5d0, 0x3b9a03a5, 0x3f254d90, 0x42e68abb
0, // invalid
0 // invalid
}; };
// lanczos2 kernel LUT // lanczos2 kernel LUT
@@ -73,24 +71,6 @@ namespace Fem {
return (int16_t)filteredSample; return (int16_t)filteredSample;
} }
uint32_t noteFrequency(uint8_t note) {
// 2048 samples / cycle ~ 48kHz / 20Hz
// uint32_t pitch accumulator coefficient
// top 11-bits = sample #
// bottom 21-bits = subsample resolution
// use a discontinuous "fast" note notation
// oooonnnn
// o = octave (0:15 = -6:9)
// n = note (0:11 = C:B)
uint32_t notePitch = NOTELUT[note & 0x0f];
uint8_t octaveShift = note >> 4;
octaveShift = (0xf - octaveShift) & 0x0f;
notePitch = notePitch >> octaveShift;
return notePitch;
}
// linear interpolation of two samples // linear interpolation of two samples
int16_t lerp(int16_t a, int16_t b, uint16_t t) { int16_t lerp(int16_t a, int16_t b, uint16_t t) {
int32_t lerpSum = (int32_t)(0x2000 - t) * (int32_t)a; int32_t lerpSum = (int32_t)(0x2000 - t) * (int32_t)a;
@@ -109,7 +89,8 @@ namespace Fem {
} }
int16_t gen(uint8_t note, uint16_t wavePos, int16_t** waveTable) { int16_t gen(uint8_t note, uint16_t wavePos, int16_t** waveTable) {
pitchAcc += noteFrequency(note); // pitchAcc += noteFrequency(note);
pitchAcc += NOTELUT[note];
// interpolate between two waves in the wavetable // interpolate between two waves in the wavetable
uint8_t waveIndex = wavePos >> 13; uint8_t waveIndex = wavePos >> 13;
scripts/midilut-gen.py
+13
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@@ -0,0 +1,13 @@
# generate a lookup table of all 128 MIDI notes
import numpy as np
for j in range(0, 128, 8):
lineString = ""
for k in range(8):
n = j + k
f = 440. * (2. ** ((n - 69.) / 12.))
y = f * (2. ** 32.) / 48000.
lineString += hex(int(y))
lineString += ", "
print(lineString)