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CMS/Game Blaster pitch correction

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This patch make more accurate CMS emulation like actual GameBlaster.
Original works of this patch from https://www.vogons.org/viewtopic.php?f=41&t=38350 for DOSBox, thanks to them.
This commit is contained in:
basic2004
2017-01-16 04:17:14 +09:00
committed by GitHub
parent 0a11edd343
commit d763969472
1 changed files with 8 additions and 6 deletions
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14
src/sound_cms.c
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@@ -7,6 +7,8 @@
#include "sound.h"
#include "sound_cms.h"
#define MASTER_CLOCK 7159090
typedef struct cms_t
{
int addrs[2];
@@ -37,9 +39,9 @@ void cms_update(cms_t *cms)
{
switch (cms->noisetype[c >> 1][c & 1])
{
case 0: cms->noisefreq[c >> 1][c & 1] = 31250; break;
case 1: cms->noisefreq[c >> 1][c & 1] = 15625; break;
case 2: cms->noisefreq[c >> 1][c & 1] = 7812; break;
case 0: cms->noisefreq[c >> 1][c & 1] = MASTER_CLOCK/256; break;
case 1: cms->noisefreq[c >> 1][c & 1] = MASTER_CLOCK/512; break;
case 2: cms->noisefreq[c >> 1][c & 1] = MASTER_CLOCK/1024; break;
case 3: cms->noisefreq[c >> 1][c & 1] = cms->freq[c >> 1][(c & 1) * 3]; break;
}
}
@@ -124,14 +126,14 @@ void cms_write(uint16_t addr, uint8_t val, void *p)
case 0x0B: case 0x0C: case 0x0D:
voice = cms->addrs[chip] & 7;
cms->latch[chip][voice] = (cms->latch[chip][voice] & 0x700) | val;
cms->freq[chip][voice] = (15625 << (cms->latch[chip][voice] >> 8)) / (511 - (cms->latch[chip][voice] & 255));
cms->freq[chip][voice] = (MASTER_CLOCK/512 << (cms->latch[chip][voice] >> 8)) / (511 - (cms->latch[chip][voice] & 255));
break;
case 0x10: case 0x11: case 0x12: /*Octave*/
voice = (cms->addrs[chip] & 3) << 1;
cms->latch[chip][voice] = (cms->latch[chip][voice] & 0xFF) | ((val & 7) << 8);
cms->latch[chip][voice + 1] = (cms->latch[chip][voice + 1] & 0xFF) | ((val & 0x70) << 4);
cms->freq[chip][voice] = (15625 << (cms->latch[chip][voice] >> 8)) / (511 - (cms->latch[chip][voice] & 255));
cms->freq[chip][voice + 1] = (15625 << (cms->latch[chip][voice + 1] >> 8)) / (511 - (cms->latch[chip][voice + 1] & 255));
cms->freq[chip][voice] = (MASTER_CLOCK/512 << (cms->latch[chip][voice] >> 8)) / (511 - (cms->latch[chip][voice] & 255));
cms->freq[chip][voice + 1] = (MASTER_CLOCK/512 << (cms->latch[chip][voice + 1] >> 8)) / (511 - (cms->latch[chip][voice + 1] & 255));
break;
case 0x16: /*Noise*/
cms->noisetype[chip][0] = val & 3;