mmc5_snd.c
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/*
** Nofrendo (c) 1998-2000 Matthew Conte (matt@conte.com)
**
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of version 2 of the GNU Library General
** Public License as published by the Free Software Foundation.
**
** This program 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 GNU
** Library General Public License for more details. To obtain a
** copy of the GNU Library General Public License, write to the Free
** Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
**
** Any permitted reproduction of these routines, in whole or in part,
** must bear this legend.
**
**
** mmc5_snd.c
**
** Nintendo MMC5 sound emulation
** $Id: mmc5_snd.c,v 1.2 2001/04/27 14:37:11 neil Exp $
*/
#include <string.h>
#include <noftypes.h>
#include "mmc5_snd.h"
#include <nes_apu.h>
/* TODO: encapsulate apu/mmc5 rectangle */
#define APU_OVERSAMPLE
#define APU_VOLUME_DECAY(x) ((x) -= ((x) >> 7))
/* look up table madness */
static int32 decay_lut[16];
static int vbl_lut[32];
/* various sound constants for sound emulation */
/* vblank length table used for rectangles, triangle, noise */
static const uint8 vbl_length[32] =
{
5, 127, 10, 1, 19, 2, 40, 3, 80, 4, 30, 5, 7, 6, 13, 7,
6, 8, 12, 9, 24, 10, 48, 11, 96, 12, 36, 13, 8, 14, 16, 15
};
/* ratios of pos/neg pulse for rectangle waves
** 2/16 = 12.5%, 4/16 = 25%, 8/16 = 50%, 12/16 = 75%
** (4-bit adder in rectangles, hence the 16)
*/
static const int duty_lut[4] =
{
2, 4, 8, 12
};
#define MMC5_WRA0 0x5000
#define MMC5_WRA1 0x5001
#define MMC5_WRA2 0x5002
#define MMC5_WRA3 0x5003
#define MMC5_WRB0 0x5004
#define MMC5_WRB1 0x5005
#define MMC5_WRB2 0x5006
#define MMC5_WRB3 0x5007
#define MMC5_SMASK 0x5015
typedef struct mmc5rectangle_s
{
uint8 regs[4];
bool enabled;
float accum;
int32 freq;
int32 output_vol;
bool fixed_envelope;
bool holdnote;
uint8 volume;
int32 env_phase;
int32 env_delay;
uint8 env_vol;
int vbl_length;
uint8 adder;
int duty_flip;
} mmc5rectangle_t;
typedef struct mmc5dac_s
{
int32 output;
bool enabled;
} mmc5dac_t;
static struct
{
float incsize;
uint8 mul[2];
mmc5rectangle_t rect[2];
mmc5dac_t dac;
} mmc5;
#define MMC5_RECTANGLE_OUTPUT chan->output_vol
static int32 mmc5_rectangle(mmc5rectangle_t *chan)
{
int32 output;
#ifdef APU_OVERSAMPLE
int num_times;
int32 total;
#endif /* APU_OVERSAMPLE */
/* reg0: 0-3=volume, 4=envelope, 5=hold, 6-7=duty cycle
** reg1: 0-2=sweep shifts, 3=sweep inc/dec, 4-6=sweep length, 7=sweep on
** reg2: 8 bits of freq
** reg3: 0-2=high freq, 7-4=vbl length counter
*/
APU_VOLUME_DECAY(chan->output_vol);
if (false == chan->enabled || 0 == chan->vbl_length)
return MMC5_RECTANGLE_OUTPUT;
/* vbl length counter */
if (false == chan->holdnote)
chan->vbl_length--;
/* envelope decay at a rate of (env_delay + 1) / 240 secs */
chan->env_phase -= 4; /* 240/60 */
while (chan->env_phase < 0)
{
chan->env_phase += chan->env_delay;
if (chan->holdnote)
chan->env_vol = (chan->env_vol + 1) & 0x0F;
else if (chan->env_vol < 0x0F)
chan->env_vol++;
}
if (chan->freq < 4)
return MMC5_RECTANGLE_OUTPUT;
chan->accum -= mmc5.incsize; /* # of cycles per sample */
if (chan->accum >= 0)
return MMC5_RECTANGLE_OUTPUT;
#ifdef APU_OVERSAMPLE
num_times = total = 0;
if (chan->fixed_envelope)
output = chan->volume << 8; /* fixed volume */
else
output = (chan->env_vol ^ 0x0F) << 8;
#endif
while (chan->accum < 0)
{
chan->accum += chan->freq;
chan->adder = (chan->adder + 1) & 0x0F;
#ifdef APU_OVERSAMPLE
if (chan->adder < chan->duty_flip)
total += output;
else
total -= output;
num_times++;
#endif
}
#ifdef APU_OVERSAMPLE
chan->output_vol = total / num_times;
#else
if (chan->fixed_envelope)
output = chan->volume << 8; /* fixed volume */
else
output = (chan->env_vol ^ 0x0F) << 8;
if (0 == chan->adder)
chan->output_vol = output;
else if (chan->adder == chan->duty_flip)
chan->output_vol = -output;
#endif
return MMC5_RECTANGLE_OUTPUT;
}
static uint8 mmc5_read(uint32 address)
{
uint32 retval;
retval = (uint32) (mmc5.mul[0] * mmc5.mul[1]);
switch (address)
{
case 0x5205:
return (uint8) retval;
case 0x5206:
return (uint8) (retval >> 8);
default:
return 0xFF;
}
}
/* mix vrcvi sound channels together */
static int32 mmc5_process(void)
{
int32 accum;
accum = mmc5_rectangle(&mmc5.rect[0]);
accum += mmc5_rectangle(&mmc5.rect[1]);
if (mmc5.dac.enabled)
accum += mmc5.dac.output;
return accum;
}
/* write to registers */
static void mmc5_write(uint32 address, uint8 value)
{
int chan;
switch (address)
{
/* rectangles */
case MMC5_WRA0:
case MMC5_WRB0:
chan = (address & 4) ? 1 : 0;
mmc5.rect[chan].regs[0] = value;
mmc5.rect[chan].volume = value & 0x0F;
mmc5.rect[chan].env_delay = decay_lut[value & 0x0F];
mmc5.rect[chan].holdnote = (value & 0x20) ? true : false;
mmc5.rect[chan].fixed_envelope = (value & 0x10) ? true : false;
mmc5.rect[chan].duty_flip = duty_lut[value >> 6];
break;
case MMC5_WRA1:
case MMC5_WRB1:
break;
case MMC5_WRA2:
case MMC5_WRB2:
chan = (address & 4) ? 1 : 0;
mmc5.rect[chan].regs[2] = value;
if (mmc5.rect[chan].enabled)
mmc5.rect[chan].freq = (((mmc5.rect[chan].regs[3] & 7) << 8) + value) + 1;
break;
case MMC5_WRA3:
case MMC5_WRB3:
chan = (address & 4) ? 1 : 0;
mmc5.rect[chan].regs[3] = value;
if (mmc5.rect[chan].enabled)
{
mmc5.rect[chan].vbl_length = vbl_lut[value >> 3];
mmc5.rect[chan].env_vol = 0;
mmc5.rect[chan].freq = (((value & 7) << 8) + mmc5.rect[chan].regs[2]) + 1;
mmc5.rect[chan].adder = 0;
}
break;
case MMC5_SMASK:
if (value & 0x01)
{
mmc5.rect[0].enabled = true;
}
else
{
mmc5.rect[0].enabled = false;
mmc5.rect[0].vbl_length = 0;
}
if (value & 0x02)
{
mmc5.rect[1].enabled = true;
}
else
{
mmc5.rect[1].enabled = false;
mmc5.rect[1].vbl_length = 0;
}
break;
case 0x5010:
if (value & 0x01)
mmc5.dac.enabled = true;
else
mmc5.dac.enabled = false;
break;
case 0x5011:
mmc5.dac.output = (value ^ 0x80) << 8;
break;
case 0x5205:
mmc5.mul[0] = value;
break;
case 0x5206:
mmc5.mul[1] = value;
break;
case 0x5114:
case 0x5115:
/* ???? */
break;
default:
break;
}
}
/* reset state of vrcvi sound channels */
static void mmc5_reset(void)
{
int i;
apu_t apu;
/* get the phase period from the apu */
apu_getcontext(&apu);
mmc5.incsize = apu.cycle_rate;
for (i = 0x5000; i < 0x5008; i++)
mmc5_write(i, 0);
mmc5_write(0x5010, 0);
mmc5_write(0x5011, 0);
}
static int mmc5_init(void)
{
int i, num_samples;
apu_t apu;
apu_getcontext(&apu);
num_samples = apu.num_samples;
/* lut used for enveloping and frequency sweeps */
for (i = 0; i < 16; i++)
decay_lut[i] = num_samples * (i + 1);
/* used for note length, based on vblanks and size of audio buffer */
for (i = 0; i < 32; i++)
vbl_lut[i] = vbl_length[i] * num_samples;
return 0;
}
static apu_memread mmc5_memread[] =
{
{ 0x5205, 0x5206, mmc5_read },
{ -1, -1, NULL }
};
static apu_memwrite mmc5_memwrite[] =
{
{ 0x5000, 0x5015, mmc5_write },
{ 0x5114, 0x5115, mmc5_write },
{ 0x5205, 0x5206, mmc5_write },
{ -1, -1, NULL }
};
apuext_t mmc5_ext =
{
mmc5_init,
NULL, /* no shutdown */
mmc5_reset,
mmc5_process,
mmc5_memread,
mmc5_memwrite
};
/*
** $Log: mmc5_snd.c,v $
** Revision 1.2 2001/04/27 14:37:11 neil
** wheeee
**
** Revision 1.1 2001/04/27 12:54:40 neil
** blah
**
** Revision 1.1.1.1 2001/04/27 07:03:54 neil
** initial
**
** Revision 1.2 2000/11/13 00:57:08 matt
** doesn't look as nasty now
**
** Revision 1.1 2000/10/24 12:19:59 matt
** changed directory structure
**
** Revision 1.16 2000/10/17 11:56:42 matt
** selectable apu base frequency
**
** Revision 1.15 2000/10/10 14:04:29 matt
** make way for bjarne
**
** Revision 1.14 2000/10/10 13:58:18 matt
** stroustrup squeezing his way in the door
**
** Revision 1.13 2000/10/08 17:50:18 matt
** appears $5114/$5115 do something
**
** Revision 1.12 2000/10/03 11:56:20 matt
** better support for optional sound ext routines
**
** Revision 1.11 2000/09/27 12:26:03 matt
** changed sound accumulators back to floats
**
** Revision 1.10 2000/09/15 13:38:40 matt
** changes for optimized apu core
**
** Revision 1.9 2000/09/15 04:58:07 matt
** simplifying and optimizing APU core
**
** Revision 1.8 2000/07/30 04:32:59 matt
** no more apu_getcyclerate hack
**
** Revision 1.7 2000/07/17 01:52:31 matt
** made sure last line of all source files is a newline
**
** Revision 1.6 2000/07/04 04:51:41 matt
** cleanups
**
** Revision 1.5 2000/07/03 02:18:53 matt
** much better external module exporting
**
** Revision 1.4 2000/06/28 22:03:51 matt
** fixed stupid oversight
**
** Revision 1.3 2000/06/20 20:46:58 matt
** minor cleanups
**
** Revision 1.2 2000/06/20 04:06:16 matt
** migrated external sound definition to apu module
**
** Revision 1.1 2000/06/20 00:06:47 matt
** initial revision
**
*/