ref: 58d2d2163839d93456f861f12ddb6d697e8ebf9c
dir: /src/SNDEMDEV.c/
/*
SNDEMDEV.c
Copyright (C) 2003 Philip Cummins, Paul C. Pratt
You can redistribute this file and/or modify it under the terms
of version 2 of the GNU General Public License as published by
the Free Software Foundation. You should have received a copy
of the license along with this file; see the file COPYING.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
license for more details.
*/
/*
SouND EMulated DEVice
Emulation of Sound in the Mac Plus could go here.
This code adapted from "Sound.c" in vMac by Philip Cummins.
*/
#ifndef AllFiles
#include "SYSDEPNS.h"
#include "MYOSGLUE.h"
#include "EMCONFIG.h"
#include "GLOBGLUE.h"
#include "MINEM68K.h"
#endif
#include "SNDEMDEV.h"
#if MySoundEnabled
#define kSnd_Main_Offset 0x0300
#define kSnd_Alt_Offset 0x5F00
#define kSnd_Main_Buffer (kRAM_Size - kSnd_Main_Offset)
#define kSnd_Alt_Buffer (kRAM_Size - kSnd_Alt_Offset)
/*
approximate volume levels of vMac, so:
x * vol_mult[SoundVolume] >> 16
+ vol_offset[SoundVolume]
= {approx} (x - kCenterSound) / (8 - SoundVolume) + kCenterSound;
*/
LOCALVAR const ui4b vol_mult[] = {
8192, 9362, 10922, 13107, 16384, 21845, 32768
};
LOCALVAR const trSoundSamp vol_offset[] = {
#if 3 == kLn2SoundSampSz
112, 110, 107, 103, 96, 86, 64, 0
#elif 4 == kLn2SoundSampSz
28672, 28087, 27307, 26215, 24576, 21846, 16384, 0
#else
#error "unsupported kLn2SoundSampSz"
#endif
};
LOCALVAR const ui4b SubTick_offset[kNumSubTicks] = {
0, 25, 50, 90, 102, 115, 138, 161,
185, 208, 231, 254, 277, 300, 323, 346
};
LOCALVAR const ui3r SubTick_n[kNumSubTicks] = {
25, 25, 40, 12, 13, 23, 23, 24,
23, 23, 23, 23, 23, 23, 23, 24
};
/*
One version of free form sound driver
spends around 18000 cycles writing
offsets 50 to 370, then around another 3000
cycles writing 0 to 50. So be done
with 0 to 50 at end of second sixtieth.
*/
/*
Different in system 6.0.4:
spends around 23500 cycles writing
offsets 90 to 370, then around another 7500
cycles writing 0 to 90. This is nastier,
because gets to be a very small gap
between where is being read and
where written. So read a bit in
advance for third subtick.
*/
/*
startup sound spends around 19500 cycles
writing offsets 0 to 370. presumably
writing offset 0 before it is read.
*/
LOCALVAR ui5b SoundInvertPhase = 0;
LOCALVAR ui4b SoundInvertState = 0;
IMPORTFUNC ui4b GetSoundInvertTime(void);
GLOBALPROC MacSound_SubTick(int SubTick)
{
ui4r actL;
tpSoundSamp p;
ui4r i;
ui5b StartOffset = SubTick_offset[SubTick];
ui4r n = SubTick_n[SubTick];
unsigned long addy =
#ifdef SoundBuffer
(SoundBuffer == 0) ? kSnd_Alt_Buffer :
#endif
kSnd_Main_Buffer;
#ifndef ln2mtb
ui3p addr = addy + (2 * StartOffset) + RAM;
#else
CPTR addr = addy + (2 * StartOffset);
#endif
ui4b SoundInvertTime = GetSoundInvertTime();
ui3b SoundVolume = SoundVolb0
| (SoundVolb1 << 1)
| (SoundVolb2 << 2);
#if dbglog_HAVE && 0
dbglog_StartLine();
dbglog_writeCStr("reading sound buffer ");
dbglog_writeHex(StartOffset);
dbglog_writeCStr(" to ");
dbglog_writeHex(StartOffset + n);
dbglog_writeReturn();
#endif
label_retry:
p = MySound_BeginWrite(n, &actL);
if (actL > 0) {
if (SoundDisable && (SoundInvertTime == 0)) {
for (i = 0; i < actL; i++) {
#if 0
*p++ = 0x00; /* this is believed more accurate */
#else
/* But this avoids more clicks. */
*p++ = kCenterSound;
#endif
}
} else {
for (i = 0; i < actL; i++) {
/* Copy sound data, high byte of each word */
*p++ =
#ifndef ln2mtb
*addr
#else
get_vm_byte(addr)
#endif
#if 4 == kLn2SoundSampSz
<< 8
#endif
;
/* Move the address on */
addr += 2;
}
if (SoundInvertTime != 0) {
ui5b PhaseIncr = (ui5b)SoundInvertTime * (ui5b)20;
p -= actL;
for (i = 0; i < actL; i++) {
if (SoundInvertPhase < 704) {
ui5b OnPortion = 0;
ui5b LastPhase = 0;
do {
if (! SoundInvertState) {
OnPortion +=
(SoundInvertPhase - LastPhase);
}
SoundInvertState = ! SoundInvertState;
LastPhase = SoundInvertPhase;
SoundInvertPhase += PhaseIncr;
} while (SoundInvertPhase < 704);
if (! SoundInvertState) {
OnPortion += 704 - LastPhase;
}
*p = (*p * OnPortion) / 704;
} else {
if (SoundInvertState) {
*p = 0;
}
}
SoundInvertPhase -= 704;
p++;
}
}
}
if (SoundVolume < 7) {
/*
Usually have volume at 7, so this
is just for completeness.
*/
ui5b mult = (ui5b)vol_mult[SoundVolume];
trSoundSamp offset = vol_offset[SoundVolume];
p -= actL;
for (i = 0; i < actL; i++) {
*p = (trSoundSamp)((ui5b)(*p) * mult >> 16) + offset;
++p;
}
}
MySound_EndWrite(actL);
n -= actL;
if (n > 0) {
goto label_retry;
}
}
}
#endif