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midi: Recalculate (and rename) the note frequency table.

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gustable[] contained plain note frequencies in milliHertz, but
was named and documented to appear like a table of magic numbers.
The values also seemed to be slightly inaccurate (up to about
0.01Hz, so probably irrelevant).

This changes the name to freqtable to make the purpose clearer, and
uses slightly better values.

Change-Id: I6b568d834c8c2c92161bed5290572a29733e28dc
This commit is contained in:
Frank Gevaerts 2013-06-16 19:11:03 +02:00 • committed by Gerrit Rockbox
parent bc4c13ee8a
commit afd482f51b
3 changed files with 28 additions and 19 deletions
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39
apps/plugins/midi/guspat.c
View file

@ -22,21 +22,30 @@
#include "guspat.h"
#include "midiutil.h"
/* This came from one of the Gravis documents */
const uint32_t gustable[]=
/* Note frequencies in milliHz, base A = 440000
* Calculated using:
* double base_a=440000;
* double offset;
* for(offset=-69;offset<=58;offset++)
* {
* int value = (int)round(base_a*pow(2,offset/12));
* printf("%d, ",value);
* }
*/
const uint32_t freqtable[]=
{
8175, 8661, 9177, 9722, 10300, 10913, 11562, 12249, 12978, 13750, 14567, 15433,
16351, 17323, 18354, 19445, 20601, 21826, 23124, 24499, 25956, 27500, 29135, 30867,
32703, 34647, 36708, 38890, 41203, 43653, 46249, 48999, 51913, 54999, 58270, 61735,
65406, 69295, 73416, 77781, 82406, 87306, 92498, 97998, 103826, 109999, 116540, 123470,
130812, 138591, 146832, 155563, 164813, 174614, 184997, 195997, 207652, 219999, 233081, 246941,
261625, 277182, 293664, 311126, 329627, 349228, 369994, 391995, 415304, 440000, 466163, 493883,
523251, 554365, 587329, 622254, 659255, 698456, 739989, 783991, 830609, 880000, 932328, 987767,
1046503, 1108731, 1174660, 1244509, 1318511, 1396914, 1479979, 1567983, 1661220, 1760002, 1864657, 1975536,
2093007, 2217464, 2349321, 2489019, 2637024, 2793830, 2959960, 3135968, 3322443, 3520006, 3729316, 3951073,
4186073, 4434930, 4698645, 4978041, 5274051, 5587663, 5919922, 6271939, 6644889, 7040015, 7458636, 7902150,
8372036, 8869863, 9397293, 9956085, 10548105, 11175328, 11839847, 12543881
};
/* C, C#, D, D#, E, F, F#, G, G#, A, A#, B */
8176, 8662, 9177, 9723, 10301, 10913, 11562, 12250, 12978, 13750, 14568, 15434,
16352, 17324, 18354, 19445, 20602, 21827, 23125, 24500, 25957, 27500, 29135, 30868,
32703, 34648, 36708, 38891, 41203, 43654, 46249, 48999, 51913, 55000, 58270, 61735,
65406, 69296, 73416, 77782, 82407, 87307, 92499, 97999, 103826, 110000, 116541, 123471,
130813, 138591, 146832, 155563, 164814, 174614, 184997, 195998, 207652, 220000, 233082, 246942,
261626, 277183, 293665, 311127, 329628, 349228, 369994, 391995, 415305, 440000, 466164, 493883,
523251, 554365, 587330, 622254, 659255, 698456, 739989, 783991, 830609, 880000, 932328, 987767,
1046502, 1108731, 1174659, 1244508, 1318510, 1396913, 1479978, 1567982, 1661219, 1760000, 1864655, 1975533,
2093005, 2217461, 2349318, 2489016, 2637020, 2793826, 2959955, 3135963, 3322438, 3520000, 3729310, 3951066,
4186009, 4434922, 4698636, 4978032, 5274041, 5587652, 5919911, 6271927, 6644875, 7040000, 7458620, 7902133,
8372018, 8869844, 9397273, 9956063, 10548082, 11175303, 11839822, 12543854 };
static unsigned int readWord(int file)
{
@ -141,7 +150,7 @@ static struct GWaveform * loadWaveform(int file)
static int selectWaveform(struct GPatch * pat, int midiNote)
{
/* We divide by 100 here because everyone's freq formula is slightly different */
unsigned int tabFreq = gustable[midiNote]/100; /* Comparison */
unsigned int tabFreq = freqtable[midiNote]/100; /* Comparison */
unsigned int a=0;
for(a=0; a<pat->numWaveforms; a++)
{