/*
** 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.
**
**
** nes_apu.c
**
** NES APU emulation
** nes_apu.c,v 1.4 2002/01/09 18:13:20 tekezo Exp
*/

/*
** Changes for nester:
** changes are marked with DCR
**
** removed bad #includes
** nullified ASSERT and log_printf
** added custom log_printf()
** #included stlib.h for malloc()
**
** - Darren Ranalli
*/

/*
** Changes for nester:
** support ExSounds
**
** - TAKEDA, toshiya
*/

#include <string.h>
#include <stdlib.h> //DCR
#include "types.h"
//DCR#include "log.h"
#include "nes_apu.h"
#include "nes6502.h"

/* included for nes_irq() and nes_clearframeirq() */
#ifndef NSF_PLAYER
//DCR#include "nes.h"
#endif /* !NSF_PLAYER */

#include "debug.h"
void
log_printf(const char *str)
{
  LOG(str);
}

#ifndef  APU_YANO
#define  APU_OVERSAMPLE
#define  APU_VOLUME_DECAY(x)  ((x) -= ((x) >> 7))
#endif /* !APU_YANO */


/* pointer to active APU */
static apu_t *apu;

/* look up table madness */
static int32 decay_lut[16];
static int vbl_lut[32];
static int trilength_lut[128];

/* noise lookups for both modes */
#ifndef REALTIME_NOISE
static int8 noise_long_lut[APU_NOISE_32K];
static int8 noise_short_lut[APU_NOISE_93];
#endif /* !REALTIME_NOISE */


/* 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
};

/* frequency limit of rectangle channels */
static const int freq_limit[8] =
{
   0x3FF, 0x555, 0x666, 0x71C, 0x787, 0x7C1, 0x7E0, 0x7F0
};

/* noise frequency lookup table */
static const int noise_freq[16] =
{
     4,    8,   16,   32,   64,   96,  128,  160,
   202,  254,  380,  508,  762, 1016, 2034, 4068
};

/* DMC transfer freqs */
const int dmc_clocks[16] =
{
   428, 380, 340, 320, 286, 254, 226, 214,
   190, 160, 142, 128, 106,  85,  72,  54
};

/* ratios of pos/neg pulse for rectangle waves */
static const int duty_lut[4] = { 2, 4, 8, 12 };

// for $4017:bit7 by T.Yano
static int apu_cnt_rate = 5;


void apu_setcontext(apu_t *src_apu)
{
   apu = src_apu;
}

apu_t *apu_getcontext(void)
{
   return apu;
}

/*
** Simple queue routines
*/
#define  APU_QEMPTY()   (apu->q_head == apu->q_tail)
#define  EX_QEMPTY()   (apu->ex_q_head == apu->ex_q_tail)

#include "nes_exsound.cpp"

static void apu_enqueue(apudata_t *d)
{
  ASSERT(apu);
  apu->queue[apu->q_head] = *d;

  apu->q_head = (apu->q_head + 1) & APUQUEUE_MASK;

  if (APU_QEMPTY())
    log_printf("apu: queue overflow\n");
}

static apudata_t *apu_dequeue(void)
{
  int loc;

  ASSERT(apu);

  if (APU_QEMPTY())
    log_printf("apu: queue empty\n");

  loc = apu->q_tail;
  apu->q_tail = (apu->q_tail + 1) & APUQUEUE_MASK;

  return &apu->queue[loc];
}

static void ex_enqueue(apudata_t *d)
{
  ASSERT(apu);
  apu->ex_queue[apu->ex_q_head] = *d;

  apu->ex_q_head = (apu->ex_q_head + 1) & APUQUEUE_MASK;

  if (EX_QEMPTY())
    log_printf("ex_apu: queue overflow\n");
}

static apudata_t *ex_dequeue(void)
{
   int loc;

   ASSERT(apu);

   if (EX_QEMPTY())
      log_printf("ex_apu: queue empty\n");

   loc = apu->ex_q_tail;
   apu->ex_q_tail = (apu->ex_q_tail + 1) & APUQUEUE_MASK;

   return &apu->ex_queue[loc];
}


/* emulation of the 15-bit shift register the
** NES uses to generate pseudo-random series
** for the white noise channel
*/
#ifdef REALTIME_NOISE
INLINE int8 shift_register15(uint8 xor_tap)
{
  static int sreg = 0x4000;
  int bit0, tap, bit14;

  bit0 = sreg & 1;
  tap = (sreg & xor_tap) ? 1 : 0;
  bit14 = (bit0 ^ tap);
  sreg >>= 1;
  sreg |= (bit14 << 14);
  return (bit0 ^ 1);
}
#else /* !REALTIME_NOISE */
static void shift_register15(int8 *buf, int count)
{
  static int sreg = 0x4000;
   int bit0, bit1, bit6, bit14;

   if (count == APU_NOISE_93)
   {
     while (count--)
     {
       bit0 = sreg & 1;
       bit6 = (sreg & 0x40) >> 6;
       bit14 = (bit0 ^ bit6);
       sreg >>= 1;
       sreg |= (bit14 << 14);
       *buf++ = bit0 ^ 1;
     }
   }
   else /* 32K noise */
   {
     while (count--)
     {
       bit0 = sreg & 1;
       bit1 = (sreg & 2) >> 1;
       bit14 = (bit0 ^ bit1);
       sreg >>= 1;
       sreg |= (bit14 << 14);
       *buf++ = bit0 ^ 1;
     }
   }
}
#endif /* !REALTIME_NOISE */

/* RECTANGLE WAVE
** ==============
** 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
*/
#define  APU_RECTANGLE_OUTPUT (chan->output_vol)
static int32
apu_rectangle(rectangle_t *chan)
{
  int32 output;

#ifdef APU_YANO
  double total;
  double sample_weight;
#else /* !APU_YANO */
#ifdef APU_OVERSAMPLE
  int num_times;
  int32 total;
#endif /* APU_OVERSAMPLE */

  APU_VOLUME_DECAY(chan->output_vol);
#endif /* !APU_YANO */

  if (FALSE == chan->enabled || chan->vbl_length <= 0)
    return APU_RECTANGLE_OUTPUT;

  /* envelope decay at a rate of (env_delay + 1) / 240 secs */
  chan->env_phase -= 4 * apu_cnt_rate; /* 240/60 */

  while (chan->env_phase < 0)
  {
    chan->env_phase += chan->env_delay;
    ++chan->env_vol;
  }

  if (chan->holdnote)
    chan->env_vol &= 0xf;
  else
  {
    /* vbl length counter */
    chan->vbl_length -= apu_cnt_rate;

    if (chan->env_vol > 0xf)
      chan->env_vol = 0xf;
  }

  /* TODO: using a table of max frequencies is not technically
  ** clean, but it is fast and (or should be) accurate
  */
  if (chan->freq < 8 || (FALSE == chan->sweep_inc && chan->freq > chan->freq_limit))
    return APU_RECTANGLE_OUTPUT;

  /* frequency sweeping at a rate of (sweep_delay + 1) / 120 secs */
  if (chan->sweep_on && chan->sweep_shifts)
  {
    chan->sweep_phase -= 2 * apu_cnt_rate; /* 120/60 */

    if (chan->sweep_inc)
    {
      if (chan->sweep_complement)
      {
        while (chan->sweep_phase < 0)
        {
          chan->sweep_phase += chan->sweep_delay;
          chan->freq += ~(chan->freq >> chan->sweep_shifts);
        }
      }
      else
      {
        while (chan->sweep_phase < 0)
        {
          chan->sweep_phase += chan->sweep_delay;
          chan->freq -= (chan->freq >> chan->sweep_shifts);
        }
      }
    }
    else
    {
      while (chan->sweep_phase < 0)
      {
        chan->sweep_phase += chan->sweep_delay;
        chan->freq += (chan->freq >> chan->sweep_shifts);
      }
    }
  }

#ifdef APU_YANO
  if (chan->fixed_envelope)
    output = chan->volume << 8; /* fixed volume */
  else
    output = (chan->env_vol ^ 0x0F) << 8;

  sample_weight = chan->phaseacc;
  if ( sample_weight > apu->cycle_rate) {
    sample_weight = apu->cycle_rate;
  }
  total = (chan->adder < chan->duty_flip)?sample_weight:-sample_weight;

  chan->phaseacc -= apu->cycle_rate; /* # of cycles per sample */
  while ( chan->phaseacc < 0) {
    chan->phaseacc += APU_TO_FIXED(chan->freq + 1);
    chan->adder = (chan->adder + 1) & 0x0F;

    sample_weight = APU_TO_FIXED(chan->freq + 1);
    if (chan->phaseacc > 0) {
      sample_weight -= chan->phaseacc;
    }
    total += (chan->adder < chan->duty_flip)?sample_weight:-sample_weight;
  }
  chan->output_vol = (int)floor( output*total/apu->cycle_rate + 0.5);
#else /* !APU_YANO */
  chan->phaseacc -= apu->cycle_rate; /* # of cycles per sample */
  if (chan->phaseacc >= 0)
    return APU_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 /* APU_OVERSAMPLE */

  while (chan->phaseacc < 0)
  {
    chan->phaseacc += APU_TO_FIXED(chan->freq + 1);
    chan->adder = (chan->adder + 1) & 0x0F;

#ifdef APU_OVERSAMPLE
    if (chan->adder < chan->duty_flip)
      total += output;
    else
      total -= output;

    num_times++;
#endif /* APU_OVERSAMPLE */
  }

#ifdef APU_OVERSAMPLE
  chan->output_vol = total / num_times;
#else /* !APU_OVERSAMPLE */
  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 /* !APU_OVERSAMPLE */
#endif /* !APU_YANO */

  return APU_RECTANGLE_OUTPUT;
}

/* TRIANGLE WAVE
** =============
** reg0: 7=holdnote, 6-0=linear length counter
** reg2: low 8 bits of frequency
** reg3: 7-3=length counter, 2-0=high 3 bits of frequency
*/
//#define  APU_TRIANGLE_OUTPUT  (chan->output_vol + (chan->output_vol >> 1))
#define  APU_TRIANGLE_OUTPUT  ((chan->output_vol*21)>>4)
static int32 apu_triangle(triangle_t *chan)
{
#ifdef APU_YANO
   static double val;
   double sample_weight, total, prev_val;
#else /* !APU_YANO */
   APU_VOLUME_DECAY(chan->output_vol);
#endif /* !APU_YANO */

   if (FALSE == chan->enabled || chan->vbl_length <= 0)
      return APU_TRIANGLE_OUTPUT;

   if (chan->counter_started)
   {
      if (chan->linear_length > 0)
         chan->linear_length -= 4 * apu_cnt_rate;  /* 240/60 */
      if (chan->vbl_length > 0 && FALSE == chan->holdnote)
         chan->vbl_length -= apu_cnt_rate;
   }
   else if (FALSE == chan->holdnote && chan->write_latency)
   {
      if (--chan->write_latency == 0)
         chan->counter_started = TRUE;
   }

   if (chan->linear_length <= 0 || chan->freq < APU_TO_FIXED(4)) /* inaudible */
      return APU_TRIANGLE_OUTPUT;

#ifdef APU_YANO
   if ( chan->ideal_triangle) {
      total = 0;
      sample_weight = 0;
      prev_val = val;
      if ( chan->adder) {
         val -= (double)apu->cycle_rate/chan->freq;
      } else {
         val += (double)apu->cycle_rate/chan->freq;
      }
      while ( (val < -8) || (val >= 8)) {
         if (val <-8) {
            total += (prev_val + (-8))*(prev_val-(-8));
            sample_weight += prev_val-(-8);
            prev_val = -8;
            val = -16-val;
            chan->adder = 0;
         }
         if (val >= 8) {
            total += (prev_val + 8)*(8-prev_val);
            sample_weight += 8-prev_val;
            prev_val = 8;
            val = 16-val;
            chan->adder = 1;
         }
      }
      if ( chan->adder) {
         total += (prev_val + val)*(prev_val-val);
         sample_weight += prev_val-val;
      } else {
         total += (prev_val + val)*(val-prev_val);
         sample_weight += val-prev_val;
      }
      total /= sample_weight;
      chan->output_vol = (int)floor(total*256+0.5);
   } else { /* !ideal_triangle */
      sample_weight = chan->phaseacc;
      if ( sample_weight > apu->cycle_rate) {
         sample_weight = apu->cycle_rate;
      }
      total = (((chan->adder & 0x10)?0x1f:0)^chan->adder)*sample_weight;

      chan->phaseacc -= apu->cycle_rate; /* # of cycles per sample */
      while ( chan->phaseacc < 0) {
         chan->phaseacc += chan->freq;
         chan->adder = (chan->adder + 1) & 0x1F;

         sample_weight = chan->freq;
         if (chan->phaseacc > 0) {
            sample_weight -= chan->phaseacc;
         }
         total += (((chan->adder & 0x10)?0x1f:0)^chan->adder)*sample_weight;
      }
      chan->output_vol = (int)floor( total*512/apu->cycle_rate + 0.5);
   }
#else /* !APU_YANO */
   chan->phaseacc -= apu->cycle_rate; /* # of cycles per sample */
   while (chan->phaseacc < 0)
   {
      chan->phaseacc += chan->freq;
      chan->adder = (chan->adder + 1) & 0x1F;

      if (chan->adder & 0x10)
         chan->output_vol -= (2 << 8);
      else
         chan->output_vol += (2 << 8);
   }
#endif /* !APU_YANO */

   return APU_TRIANGLE_OUTPUT;
}


/* WHITE NOISE CHANNEL
** ===================
** reg0: 0-3=volume, 4=envelope, 5=hold
** reg2: 7=small(93 byte) sample,3-0=freq lookup
** reg3: 7-4=vbl length counter
*/
//#define  APU_NOISE_OUTPUT  (chan->output_vol - (chan->output_vol >> 2))
#define  APU_NOISE_OUTPUT  ((chan->output_vol*13)>>4)

static int32 apu_noise(noise_t *chan)
{
  int32 outvol;

#ifdef APU_YANO
  static int32 noise_bit;
  double total;
  double sample_weight;
#else /* !APU_YANO */
#if defined(APU_OVERSAMPLE) && defined(REALTIME_NOISE)
#else /* !(APU_OVERSAMPLE && REALTIME_NOISE) */
  int32 noise_bit;
#endif /* !(APU_OVERSAMPLE && REALTIME_NOISE) */
#ifdef APU_OVERSAMPLE
  int num_times;
  int32 total;
#endif /* APU_OVERSAMPLE */

  APU_VOLUME_DECAY(chan->output_vol);
#endif /* !APU_YANO */

  if (FALSE == chan->enabled || chan->vbl_length <= 0)
    return APU_NOISE_OUTPUT;

  /* envelope decay at a rate of (env_delay + 1) / 240 secs */
  chan->env_phase -= 4 * apu_cnt_rate; /* 240/60 */

  while (chan->env_phase < 0)
  {
    chan->env_phase += chan->env_delay;
    ++chan->env_vol;
  }

  if (chan->holdnote)
    chan->env_vol &= 0xf;
  else
  {
    /* vbl length counter */
    chan->vbl_length -= apu_cnt_rate;

    if (chan->env_vol > 0xf)
      chan->env_vol = 0xf;
  }

#ifdef APU_YANO
  if (chan->fixed_envelope)
    outvol = chan->volume << 8; /* fixed volume */
  else
    outvol = (chan->env_vol ^ 0x0F) << 8;

  sample_weight = chan->phaseacc;
  if ( sample_weight > apu->cycle_rate) {
    sample_weight = apu->cycle_rate;
  }
  total = noise_bit ? sample_weight:-sample_weight;

  chan->phaseacc -= apu->cycle_rate; /* # of cycles per sample */
  while ( chan->phaseacc < 0) {
    chan->phaseacc += chan->freq;

#ifdef REALTIME_NOISE
    noise_bit = shift_register15(chan->xor_tap);
#else /* !REALTIME_NOISE */
    chan->cur_pos++;

    if (chan->short_sample)
    {
      if (APU_NOISE_93 == chan->cur_pos)
        chan->cur_pos = 0;
    }
    else
    {
      if (APU_NOISE_32K == chan->cur_pos)
        chan->cur_pos = 0;
    }

    if (chan->short_sample)
      noise_bit = noise_short_lut[chan->cur_pos];
    else
      noise_bit = noise_long_lut[chan->cur_pos];
#endif /* !REALTIME_NOISE */

    sample_weight = chan->freq;
    if (chan->phaseacc > 0) {
      sample_weight -= chan->phaseacc;
    }
    total += noise_bit ? sample_weight:-sample_weight;
  }
  chan->output_vol = (int)floor( outvol*total/apu->cycle_rate + 0.5);
#else /* !APU_YANO */
  chan->phaseacc -= apu->cycle_rate; /* # of cycles per sample */
  if (chan->phaseacc >= 0)
    return APU_NOISE_OUTPUT;

#ifdef APU_OVERSAMPLE
  num_times = total = 0;

  if (chan->fixed_envelope)
    outvol = chan->volume << 8; /* fixed volume */
  else
    outvol = (chan->env_vol ^ 0x0F) << 8;
#endif /* APU_OVERSAMPLE */

  while (chan->phaseacc < 0)
  {
    chan->phaseacc += chan->freq;

#ifdef REALTIME_NOISE

#ifdef APU_OVERSAMPLE
    if (shift_register15(chan->xor_tap))
      total += outvol;
    else
      total -= outvol;

    num_times++;
#else /* !APU_OVERSAMPLE */
    noise_bit = shift_register15(chan->xor_tap);
#endif /* !APU_OVERSAMPLE */

#else /* !REALTIME_NOISE */
    chan->cur_pos++;

    if (chan->short_sample)
    {
      if (APU_NOISE_93 == chan->cur_pos)
        chan->cur_pos = 0;
    }
    else
    {
      if (APU_NOISE_32K == chan->cur_pos)
        chan->cur_pos = 0;
    }

#ifdef APU_OVERSAMPLE
    if (chan->short_sample)
      noise_bit = noise_short_lut[chan->cur_pos];
    else
      noise_bit = noise_long_lut[chan->cur_pos];

    if (noise_bit)
      total += outvol;
    else
      total -= outvol;

    num_times++;
#endif /* APU_OVERSAMPLE */
#endif /* !REALTIME_NOISE */
  }

#ifdef APU_OVERSAMPLE
  chan->output_vol = total / num_times;
#else /* !APU_OVERSAMPLE */
  if (chan->fixed_envelope)
    outvol = chan->volume << 8; /* fixed volume */
  else
    outvol = (chan->env_vol ^ 0x0F) << 8;

#ifndef REALTIME_NOISE
  if (chan->short_sample)
    noise_bit = noise_short_lut[chan->cur_pos];
  else
    noise_bit = noise_long_lut[chan->cur_pos];
#endif /* !REALTIME_NOISE */

  if (noise_bit)
    chan->output_vol = outvol;
  else
    chan->output_vol = -outvol;
#endif /* !APU_OVERSAMPLE */
#endif /* !APU_YANO */

  return APU_NOISE_OUTPUT;
}


INLINE void apu_dmcreload(dmc_t *chan)
{
  chan->address = chan->cached_addr;
  chan->dma_length = chan->cached_dmalength;
  chan->irq_occurred = FALSE;
}

/* DELTA MODULATION CHANNEL
** =========================
** reg0: 7=irq gen, 6=looping, 3-0=pointer to clock table
** reg1: output dc level, 6 bits unsigned
** reg2: 8 bits of 64-byte aligned address offset : $C000 + (value * 64)
** reg3: length, (value * 16) + 1
*/
//#define  APU_DMC_OUTPUT (chan->output_vol - (chan->output_vol >> 3))
#define  APU_DMC_OUTPUT ((chan->output_vol*13)>>4)
static int32 apu_dmc(dmc_t *chan)
{
#ifdef APU_YANO
  double total;
  double sample_weight;
#endif /* APU_YANO */
  int delta_bit;

#ifndef APU_YANO
  APU_VOLUME_DECAY(chan->output_vol);
#endif /* !APU_YANO */

  /* only process when channel is alive */
  if (chan->dma_length)
  {
#ifdef APU_YANO
    sample_weight = chan->phaseacc;
    if ( sample_weight > apu->cycle_rate) {
      sample_weight = apu->cycle_rate;
    }
    total = (chan->regs[1]<<8)*sample_weight;
#endif /* APU_YANO */
    chan->phaseacc -= apu->cycle_rate; /* # of cycles per sample */

    while (chan->phaseacc < 0)
    {
      chan->phaseacc += chan->freq;

      if (0 == (chan->dma_length & 7))
      {
        chan->cur_byte = nes6502_getbyte(chan->address);

        /* steal a cycle from CPU*/
        nes6502_burn(1); // for New nes6502.c v1.23 by matt
//            nes6502_setdma(1); // for nes6502.c v1.4 by matt

        if (0xFFFF == chan->address)
          chan->address = 0x8000;
        else
          chan->address++;
      }

      if (--chan->dma_length == 0)
      {
        /* if loop bit set, we're cool to retrigger sample */
        if (chan->looping)
          apu_dmcreload(chan);
        else
        {
          /* check to see if we should generate an irq */
          if (chan->irq_gen)
          {
            chan->irq_occurred = TRUE;
#ifndef NSF_PLAYER
//DCR                  nes_irq();
#endif /* !NSF_PLAYER */
          }

          /* bodge for timestamp queue */
#ifdef APU_YANO
          sample_weight = chan->freq - chan->phaseacc;
          total += (chan->regs[1]<<8)*sample_weight;
          while ( chan->phaseacc < 0) chan->phaseacc += chan->freq;
#endif /* !APU_YANO */
          chan->enabled = FALSE;
          break;
        }
      }
      delta_bit = (chan->dma_length & 7) ^ 7;

      /* positive delta */
      if (chan->cur_byte & (1 << delta_bit))
      {
        if (chan->regs[1] < 0x7D)
        {
          chan->regs[1] += 2;
#ifndef APU_YANO
          chan->output_vol += (2 << 8);
#endif /* !APU_YANO */
        }
      }
      /* negative delta */
      else
      {
        if (chan->regs[1] > 1)
        {
          chan->regs[1] -= 2;
#ifndef APU_YANO
          chan->output_vol -= (2 << 8);
#endif /* !APU_YANO */
        }
      }
#ifdef APU_YANO
      sample_weight = chan->freq;
      if (chan->phaseacc > 0) {
        sample_weight -= chan->phaseacc;
      }
      total += (chan->regs[1]<<8)*sample_weight;
#endif /* !APU_YANO */
    }
#ifdef APU_YANO
    chan->output_vol = (int)floor( total/apu->cycle_rate + 0.5);
#endif /* !APU_YANO */
  }
#ifdef APU_YANO
  else
  {
    chan->output_vol = chan->regs[1] << 8;
  }
#endif /* !APU_YANO */

  return APU_DMC_OUTPUT;
}


static void apu_regwrite(uint32 address, uint8 value)
{
  int chan;

  ASSERT(apu);

  switch (address)
  {
    /* rectangles */
    case APU_WRA0:
    case APU_WRB0:
      chan = (address & 4) ? 1 : 0;
      apu->apus.rectangle[chan].regs[0] = value;

      apu->apus.rectangle[chan].volume = value & 0x0F;
      apu->apus.rectangle[chan].env_delay = decay_lut[value & 0x0F];
      apu->apus.rectangle[chan].holdnote = (value & 0x20) ? TRUE : FALSE;
      apu->apus.rectangle[chan].fixed_envelope = (value & 0x10) ? TRUE : FALSE;
      apu->apus.rectangle[chan].duty_flip = duty_lut[value >> 6];
      break;

    case APU_WRA1:
    case APU_WRB1:
      chan = (address & 4) ? 1 : 0;
      apu->apus.rectangle[chan].regs[1] = value;
      apu->apus.rectangle[chan].sweep_on = (value & 0x80) ? TRUE : FALSE;
      apu->apus.rectangle[chan].sweep_shifts = value & 7;
      apu->apus.rectangle[chan].sweep_delay = decay_lut[(value >> 4) & 7];
      apu->apus.rectangle[chan].sweep_inc = (value & 0x08) ? TRUE : FALSE;
      apu->apus.rectangle[chan].freq_limit = freq_limit[value & 7];
      break;

    case APU_WRA2:
    case APU_WRB2:
      chan = (address & 4) ? 1 : 0;
      apu->apus.rectangle[chan].regs[2] = value;
      apu->apus.rectangle[chan].freq = (apu->apus.rectangle[chan].freq & ~0xFF) | value;
      break;

    case APU_WRA3:
    case APU_WRB3:
      chan = (address & 4) ? 1 : 0;
      apu->apus.rectangle[chan].regs[3] = value;

      apu->apus.rectangle[chan].vbl_length = vbl_lut[value >> 3];
      apu->apus.rectangle[chan].env_vol = 0;
      apu->apus.rectangle[chan].freq = ((value & 7) << 8) | (apu->apus.rectangle[chan].freq & 0xFF);
      apu->apus.rectangle[chan].adder = 0;
      if ( apu->enable_reg & (1<<chan))
        apu->apus.rectangle[chan].enabled = TRUE;
      break;

      /* triangle */
    case APU_WRC0:
      apu->apus.triangle.regs[0] = value;
      apu->apus.triangle.holdnote = (value & 0x80) ? TRUE : FALSE;

      if (FALSE == apu->apus.triangle.counter_started && apu->apus.triangle.vbl_length > 0)
        apu->apus.triangle.linear_length = trilength_lut[value & 0x7F];
      break;

    case APU_WRC2:

      apu->apus.triangle.regs[1] = value;
      apu->apus.triangle.freq = APU_TO_FIXED((((apu->apus.triangle.regs[2] & 7) << 8) + value) + 1);
      break;

    case APU_WRC3:

      apu->apus.triangle.regs[2] = value;

      /* this is somewhat of a hack.  there appears to be some latency on
      ** the Real Thing between when trireg0 is written to and when the
      ** linear length counter actually begins its countdown.  we want to
      ** prevent the case where the program writes to the freq regs first,
      ** then to reg 0, and the counter accidentally starts running because
      ** of the sound queue's timestamp processing.
      **
      ** set latency to a couple hundred cycles -- should be plenty of time
      ** for the 6502 code to do a couple of table dereferences and load up
      ** the other triregs
      */

      /* 06/13/00 MPC -- seems to work OK */
      apu->apus.triangle.write_latency = (int) (228 / APU_FROM_FIXED(apu->cycle_rate));

      apu->apus.triangle.freq = APU_TO_FIXED((((value & 7) << 8) + apu->apus.triangle.regs[1]) + 1);
      apu->apus.triangle.vbl_length = vbl_lut[value >> 3];
      apu->apus.triangle.counter_started = FALSE;
      apu->apus.triangle.linear_length = trilength_lut[apu->apus.triangle.regs[0] & 0x7F];
      if ( apu->enable_reg & 0x04) apu->apus.triangle.enabled = TRUE;
      break;

      /* noise */
    case APU_WRD0:
      apu->apus.noise.regs[0] = value;
      apu->apus.noise.env_delay = decay_lut[value & 0x0F];
      apu->apus.noise.holdnote = (value & 0x20) ? TRUE : FALSE;
      apu->apus.noise.fixed_envelope = (value & 0x10) ? TRUE : FALSE;
      apu->apus.noise.volume = value & 0x0F;
      break;

    case APU_WRD2:
      apu->apus.noise.regs[1] = value;
      apu->apus.noise.freq = APU_TO_FIXED(noise_freq[value & 0x0F]);

#ifdef REALTIME_NOISE
      apu->apus.noise.xor_tap = (value & 0x80) ? 0x40: 0x02;
#else /* !REALTIME_NOISE */
      /* detect transition from long->short sample */
      if ((value & 0x80) && FALSE == apu->apus.noise.short_sample)
      {
        /* recalculate short noise buffer */
        shift_register15(noise_short_lut, APU_NOISE_93);
        apu->apus.noise.cur_pos = 0;
      }
      apu->apus.noise.short_sample = (value & 0x80) ? TRUE : FALSE;
#endif /* !REALTIME_NOISE */
      break;

    case APU_WRD3:
      apu->apus.noise.regs[2] = value;

      apu->apus.noise.vbl_length = vbl_lut[value >> 3];
      apu->apus.noise.env_vol = 0; /* reset envelope */
      if ( apu->enable_reg & 0x08) apu->apus.noise.enabled = TRUE;
      break;

      /* DMC */
    case APU_WRE0:
      apu->apus.dmc.regs[0] = value;

      apu->apus.dmc.freq = APU_TO_FIXED(dmc_clocks[value & 0x0F]);
      apu->apus.dmc.looping = (value & 0x40) ? TRUE : FALSE;

      if (value & 0x80)
        apu->apus.dmc.irq_gen = TRUE;
      else
      {
        apu->apus.dmc.irq_gen = FALSE;
        apu->apus.dmc.irq_occurred = FALSE;
      }
      break;

    case APU_WRE1: /* 7-bit DAC */
      /* add the _delta_ between written value and
      ** current output level of the volume reg
      */
      value &= 0x7F; /* bit 7 ignored */
#ifndef APU_YANO
      apu->apus.dmc.output_vol += ((value - apu->apus.dmc.regs[1]) << 8);
#endif /* !APU_YANO */
      apu->apus.dmc.regs[1] = value;
      break;

    case APU_WRE2:
      apu->apus.dmc.regs[2] = value;
      apu->apus.dmc.cached_addr = 0xC000 + (uint16) (value << 6);
      break;

    case APU_WRE3:
      apu->apus.dmc.regs[3] = value;
      apu->apus.dmc.cached_dmalength = ((value << 4) + 1) << 3;
      break;

    case APU_SMASK:
      /* bodge for timestamp queue */
      apu->apus.dmc.enabled = (value & 0x10) ? TRUE : FALSE;

      apu->enable_reg = value;

      for (chan = 0; chan < 2; chan++)
      {
        if (0 == (value & (1 << chan)) )
        {
          apu->apus.rectangle[chan].enabled = FALSE;
          apu->apus.rectangle[chan].vbl_length = 0;
        }
      }

      if (0 == (value & 0x04))
      {
        apu->apus.triangle.enabled = FALSE;
        apu->apus.triangle.vbl_length = 0;
        apu->apus.triangle.linear_length = 0;
        apu->apus.triangle.counter_started = FALSE;
        apu->apus.triangle.write_latency = 0;
      }

      if (0 == (value & 0x08))
      {
        apu->apus.noise.enabled = FALSE;
        apu->apus.noise.vbl_length = 0;
      }

      if (value & 0x10)
      {
        if (0 == apu->apus.dmc.dma_length)
          apu_dmcreload(&apu->apus.dmc);
      }
      else
      {
        apu->apus.dmc.dma_length = 0;
        apu->apus.dmc.irq_occurred = FALSE;
      }
      break;

      /* unused, but they get hit in some mem-clear loops */
    case 0x4009:
    case 0x400D:
      break;

    case 0x4017:
      if (value & 0x80)
        apu_cnt_rate = 4;
      else
        apu_cnt_rate = 5;
      break;

    default:
      break;
  }
}

/* Read from $4000-$4017 */
uint8 apu_read(uint32 address)
{
   uint8 value;

   ASSERT(apu);

   switch (address)
   {
   case APU_SMASK:
      value = 0;
      /* Return 1 in 0-5 bit pos if a channel is playing */
      if (apu->apus.rectangle[0].enabled_cur && apu->apus.rectangle[0].vbl_length_cur>0)
         value |= 0x01;
      if (apu->apus.rectangle[1].enabled_cur && apu->apus.rectangle[1].vbl_length_cur>0)
         value |= 0x02;
      if (apu->apus.triangle.enabled_cur && apu->apus.triangle.vbl_length_cur>0)
         value |= 0x04;
      if (apu->apus.noise.enabled_cur && apu->apus.noise.vbl_length_cur>0)
         value |= 0x08;
      /* bodge for timestamp queue */
      if (apu->apus.dmc.enabled_cur)
         value |= 0x10;
      if (apu->apus.dmc.irq_occurred_cur)
         value |= 0x80;
      break;

   default:
      value = (address >> 8); /* heavy capacitance on data bus */
      break;
   }

   return value;
}

uint8 ex_read(uint32 address)
{
  if (apu->exsound_type == NES_APU_EXSOUND_FDS)
  {
    return FDSSoundRead (address);
  }
  else if (apu->exsound_type == NES_APU_EXSOUND_N106)
  {
    //return N106SoundReadData (address);
    apudata_t d;
    d.timestamp = nes6502_getcycles();
    d.address = address + 0x10000;
    ex_enqueue(&d);
    return 0x00;
  }
  else
  {
    return 0x00;
  }
}

void apu_write(uint32 address, uint8 value)
{
   apudata_t d;

   switch (address)
   {
   case 0x4015:
      /* bodge for timestamp queue */
      apu->apus.dmc.enabled = (value & 0x10) ? TRUE : FALSE;

   case 0x4000: case 0x4001: case 0x4002: case 0x4003:
   case 0x4004: case 0x4005: case 0x4006: case 0x4007:
   case 0x4008: case 0x4009: case 0x400A: case 0x400B:
   case 0x400C: case 0x400D: case 0x400E: case 0x400F:
   case 0x4010: case 0x4011: case 0x4012: case 0x4013:
   case 0x4017:
      d.timestamp = nes6502_getcycles();
      d.address = address;
      d.value = value;
      apu_enqueue(&d);
      break;

   default:
      break;
   }
}

void apu_write_cur(uint32 address, uint8 value)
{
   /* for sync read $4015 */
   int chan;
   switch (address)
   {
   case APU_WRA0:
   case APU_WRB0:
      chan = (address & 4) ? 1 : 0;
      apu->apus.rectangle[chan].holdnote_cur = (value & 0x20) ? TRUE : FALSE;
      break;
   case APU_WRA3:
   case APU_WRB3:
      chan = (address & 4) ? 1 : 0;
      apu->apus.rectangle[chan].vbl_length_cur = vbl_length[value >> 3] * 5;
      if (apu->enable_reg_cur & (1<<chan))
         apu->apus.rectangle[chan].enabled_cur = TRUE;
      break;
   case APU_WRC0:
      apu->apus.triangle.holdnote_cur = (value & 0x80) ? TRUE : FALSE;
      break;
   case APU_WRC3:
      apu->apus.triangle.vbl_length_cur = vbl_length[value >> 3] * 5;
      if (apu->enable_reg_cur & 0x04)
         apu->apus.triangle.enabled_cur = TRUE;
      apu->apus.triangle.counter_started_cur = TRUE;
      break;
   case APU_WRD0:
      apu->apus.noise.holdnote_cur = (value & 0x20) ? TRUE : FALSE;
      break;
   case APU_WRD3:
      apu->apus.noise.vbl_length_cur = vbl_length[value >> 3] * 5;
      if (apu->enable_reg_cur & 0x08)
         apu->apus.noise.enabled_cur = TRUE;
      break;
   case APU_WRE0:
      apu->apus.dmc.freq_cur = dmc_clocks[value & 0x0F];
      apu->apus.dmc.phaseacc_cur = 0;
      apu->apus.dmc.looping_cur = (value & 0x40) ? TRUE : FALSE;
      if (value & 0x80)
         apu->apus.dmc.irq_gen_cur = TRUE;
      else
      {
         apu->apus.dmc.irq_gen_cur = FALSE;
         apu->apus.dmc.irq_occurred_cur = FALSE;
      }
      break;
   case APU_WRE3:
      apu->apus.dmc.cached_dmalength_cur = (value << 4) + 1;
      break;
   case APU_SMASK:
      apu->enable_reg_cur = value;
      for (chan = 0; chan < 2; chan++)
      {
         if (0 == (value & (1 << chan)))
         {
            apu->apus.rectangle[chan].enabled_cur = FALSE;
            apu->apus.rectangle[chan].vbl_length_cur = 0;
         }
      }
      if (0 == (value & 0x04))
      {
         apu->apus.triangle.enabled_cur = FALSE;
         apu->apus.triangle.vbl_length_cur = 0;
         apu->apus.triangle.counter_started_cur = FALSE;
      }
      if (0 == (value & 0x08))
      {
         apu->apus.noise.enabled_cur = FALSE;
         apu->apus.noise.vbl_length_cur = 0;
      }
      if (value & 0x10)
      {
         if(0 == apu->apus.dmc.dma_length_cur)
         {
           apu->apus.dmc.dma_length_cur = apu->apus.dmc.cached_dmalength_cur;
         }
         apu->apus.dmc.enabled_cur = TRUE;
      }
      else
      {
         apu->apus.dmc.dma_length_cur = 0;
         apu->apus.dmc.enabled_cur = FALSE;
         apu->apus.dmc.irq_occurred_cur = FALSE;
      }
      break;
   }
}

void ex_write(uint32 address, uint8 value)
{
  apudata_t d;
  d.timestamp = nes6502_getcycles();
  d.address = address;
  d.value = value;
  ex_enqueue(&d);

  if (apu->exsound_type == NES_APU_EXSOUND_FDS)
    FDSSoundWriteCurrent(address, value);
}


void apu_process(void *buffer, int num_samples)
{
  apudata_t *d;
  uint32 elapsed_cycles;
  static int32 prev_sample = 0;
  int32 next_sample, accum;

  ASSERT(apu);

  /* grab it, keep it local for speed */
  elapsed_cycles = (uint32) apu->elapsed_cycles;

  if (NULL == buffer)
  {
    /* just go through the motions... */
    while (num_samples--)
    {
      while ((FALSE == APU_QEMPTY()) &&
             (apu->queue[apu->q_tail].timestamp <= elapsed_cycles))
      {
        d = apu_dequeue();
        apu_regwrite(d->address, d->value);
      }

      if (apu->exsound.write_func)
      {
        while((FALSE == EX_QEMPTY()) &&
              apu->ex_queue[apu->ex_q_tail].timestamp <= elapsed_cycles)
        {
          d = ex_dequeue();
          (apu->exsound.write_func)(d->address, d->value);
        }
      }

      elapsed_cycles += APU_FROM_FIXED(apu->cycle_rate);
    }
  }
  else
  {
    /* bleh */
    while (num_samples--)
    {
      while ((FALSE == APU_QEMPTY()) &&
             (apu->queue[apu->q_tail].timestamp <= elapsed_cycles))
      {
        d = apu_dequeue();
        apu_regwrite(d->address, d->value);
      }

      if (apu->exsound.write_func)
      {
        while((FALSE == EX_QEMPTY()) &&
              apu->ex_queue[apu->ex_q_tail].timestamp <= elapsed_cycles)
        {
          d = ex_dequeue();
          (apu->exsound.write_func)(d->address, d->value);
        }
      }

      elapsed_cycles += APU_FROM_FIXED(apu->cycle_rate);

      accum = 0;
      accum += apu_rectangle(&apu->apus.rectangle[0]);
      accum += apu_rectangle(&apu->apus.rectangle[1]);
      accum += apu_triangle(&apu->apus.triangle);
      accum += apu_noise(&apu->apus.noise);
      accum += apu_dmc(&apu->apus.dmc);

      if (apu->exsound.render_func)
        accum += (apu->exsound.render_func)();

      /* little extra kick for the kids */
//         accum <<= 1;
/* Overflow fixed by T.Yano Dec.12.2000 */
#ifdef APU_YANO
      // Cancel DC offset Dec.17.2000
      {
        static double ave, max, min;
        double delta;
        delta = (max-min)/32768.0;
        max -= delta;
        min += delta;
        if (accum>max) max=accum;
        if (accum<min) min=accum;
        ave -= ave/1024.0;
        ave += (max+min)/2048.0;
        accum -= (int32)ave;
      }
#ifdef APU_HPF_ENABLE
      { // Just test (1/167 for 44.1k)
        static double lpf_out;
        lpf_out *=166.0/167.0;
        lpf_out += accum/167.0;
        accum -= (int32) lpf_out;
      }
#endif /* APU_HPF_ENABLE */
#endif /* APU_YANO */

      /* prevent clipping */
      if (accum > 0x7FFF)
        accum = 0x7FFF;
      else if (accum < -0x8000)
        accum = -0x8000;

      /* signed 16-bit output, unsigned 8-bit */
      if (16 == apu->sample_bits) {
        int16 *t = buffer;
        *t++ = accum;
        buffer = t;
      } else {
        uint8 *t = buffer;
        *t++ = (accum >> 8) ^ 0x80;
        buffer = t;
      }
    }
  }

  /* resync cycle counter */
  apu->elapsed_cycles = nes6502_getcycles();
}


// apu_reset_apus() added by T.Yano
void apu_reset_apus(APUSOUND *apus)
{
   int i;

   // Reset rectangles
   for ( i=0; i<2; i++) {
      memset(&apus->rectangle[i], 0, sizeof(apus->rectangle[i]));
   }
   apus->rectangle[0].sweep_complement = TRUE;
   apus->rectangle[1].sweep_complement = FALSE;
#ifdef APU_YANO
   mode = apus->triangle.ideal_triangle;
#endif
   memset(&apus->triangle, 0, sizeof(apus->triangle));
#ifdef APU_YANO
   apus->triangle.ideal_triangle = mode;
#endif
   memset(&apus->noise, 0, sizeof(apus->noise));
   memset(&apus->dmc, 0, sizeof(apus->dmc));
}

void apu_reset(void)
{
   uint32 address;

   ASSERT(apu);

   apu->elapsed_cycles = 0;
   memset(&apu->queue, 0, APUQUEUE_SIZE * sizeof(apudata_t));
   apu->q_head = apu->q_tail = 0;

   memset(&apu->ex_queue, 0, APUQUEUE_SIZE * sizeof(apudata_t));
   apu->ex_q_head = apu->ex_q_tail = 0;
   apu_set_exsound (NES_APU_EXSOUND_NONE);
   apu->exsound_enable = 1;

   // added by T.Yano
   apu_reset_apus( &apu->apus);
   apu->enable_reg = 0;
   apu->enable_reg_cur = 0;

   /* use to avoid bugs =) */
   for (address = 0x4000; address <= 0x4013; address++)
   {
      apu_regwrite(address, 0);
      apu_write_cur(address, 0);
   }

#ifdef NSF_PLAYER
   apu_regwrite(0x400C, 0x10); /* silence noise channel on NSF start */
   apu_regwrite(0x4015, 0x0F);
   apu_write_cur(0x400c, 0x10);
   apu_write_cur(0x4015, 0x0F);
#else /* !NSF_PLAYER */
   apu_regwrite(0x4015, 0x00);
   apu_write_cur(0x4015, 0x00);
#endif /* !NSF_PLAYER */

   // for ExSound
   LogTableInitialize ();
   FDSSoundReset();
   FDSSoundVolume(1);
   PSGSoundReset();
   PSGSoundVolume(1);
   N106SoundReset();
   N106SoundVolume(1);
   VRC6SoundReset();
   VRC6SoundVolume(1);
   OPLLSoundReset();
   OPLLSoundVolume(1);
   MMC5SoundReset();
   MMC5SoundVolume(1);

   // for $4017:bit7 by T.Yano
   apu_cnt_rate = 5;
}

void apu_build_luts(int num_samples)
{
  int i;

  // decay_lut[], vbl_lut[], trilength_lut[] modified (x5) for $4017:bit7 by T.Yano
  /* lut used for enveloping and frequency sweeps */
  for (i = 0; i < 16; i++)
    decay_lut[i] = num_samples * (i + 1) * 5;

  /* 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 * 5;

  /* triangle wave channel's linear length table */
  for (i = 0; i < 128; i++)
    trilength_lut[i] = num_samples * i * 5;

#ifndef REALTIME_NOISE
  /* generate noise samples */
  shift_register15(noise_long_lut, APU_NOISE_32K);
  shift_register15(noise_short_lut, APU_NOISE_93);
#endif /* !REALTIME_NOISE */
}

static void apu_setactive(apu_t *active)
{
  ASSERT(active);
  apu = active;
}

void apu_setparams(int sample_rate, int refresh_rate, int sample_bits)
{
  apu->sample_rate = sample_rate;
  apu->refresh_rate = refresh_rate;
  apu->sample_bits = sample_bits;

  /* turn into fixed point! */
  apu->cycle_rate = (int32) (APU_BASEFREQ * 65536.0 / (float) sample_rate);

  /* build various lookup tables for apu */
  apu_build_luts(sample_rate / refresh_rate);
}

void
apu_set_exsound(nes_apu_exsound_type_t ex_type)
{
  nes_apu_exsound_t *p = &(apu->exsound);

  apu->exsound_type = ex_type;

  switch (ex_type)
  {
    case NES_APU_EXSOUND_VRC6:
      p->render_func = VRC6SoundRender;
      p->write_func = VRC6SoundWrite;
      break;

    case NES_APU_EXSOUND_VRC7:
      p->render_func = OPLLSoundRender;
      p->write_func = OPLLSoundWrite;
      break;

    case NES_APU_EXSOUND_FDS:
      p->render_func = FDSSoundRender;
      p->write_func = FDSSoundWrite;
      break;

    case NES_APU_EXSOUND_MMC5:
      p->render_func = MMC5SoundRender;
      p->write_func = MMC5SoundWrite;
      break;

    case NES_APU_EXSOUND_N106:
      p->render_func = N106SoundRender;
      p->write_func = N106SoundWrite;
      break;

    case NES_APU_EXSOUND_FME7:
      p->render_func = PSGSoundRender;
      p->write_func = PSGSoundWrite;
      break;

    default:
      p->render_func = NULL;
      p->write_func = NULL;
      break;
  }

  if (!(apu->exsound_enable))
    p->render_func = NULL;
}


void
apu_set_exsound_enable(int enable)
{
  apu->exsound_enable = enable;
  apu_set_exsound(apu->exsound_type);
}


#ifdef APU_YANO
void apu_setmode(int item, int mode)
{
   switch (item) {
   case APUMODE_IDEAL_TRIANGLE:
      if ( apu != NULL) apu->apus.triangle.ideal_triangle = mode;
      break;
   case APUMODE_SMOOTH_ENVELOPE:
   case APUMODE_SMOOTH_SWEEP:
   default:
      break;
   }
}
#endif /* APU_YANO */

/* Initializes emulated sound hardware, creates waveforms/voices */
apu_t *apu_create(int sample_rate, int refresh_rate, int frag_size, int sample_bits)
{
  apu_t *temp_apu;
  int channel;

  temp_apu = malloc(sizeof(apu_t));
  if (NULL == temp_apu)
    return NULL;

  /* set the stupid flag to tell difference between two rectangles */
  temp_apu->apus.rectangle[0].sweep_complement = TRUE;
  temp_apu->apus.rectangle[1].sweep_complement = FALSE;

  apu_setactive(temp_apu);

  apu_setparams(sample_rate, refresh_rate, sample_bits);
  apu_reset(); //DCR

#ifdef APU_YANO
  apu_setmode(APUMODE_IDEAL_TRIANGLE, FALSE);
#endif /* APU_YANO */

  return temp_apu;
}

void apu_destroy(apu_t **src_apu)
{
  if (*src_apu)
    free(*src_apu);
}

void sync_apu_register()
{
   if (!apu->apus.rectangle[0].holdnote_cur && apu->apus.rectangle[0].vbl_length_cur > 0)
   {
      apu->apus.rectangle[0].vbl_length_cur -= apu_cnt_rate;
   }
   if (!apu->apus.rectangle[1].holdnote_cur && apu->apus.rectangle[1].vbl_length_cur > 0)
   {
      apu->apus.rectangle[1].vbl_length_cur -= apu_cnt_rate;
   }
   if (apu->apus.triangle.counter_started_cur)
   {
      if (apu->apus.triangle.vbl_length_cur > 0 && !apu->apus.triangle.holdnote_cur)
      {
         apu->apus.triangle.vbl_length_cur -= apu_cnt_rate;
      }
   }
   if (!apu->apus.noise.holdnote_cur && apu->apus.noise.vbl_length_cur > 0)
   {
      apu->apus.noise.vbl_length_cur -= apu_cnt_rate;
   }
}

boolean sync_dmc_register(uint32 cpu_cycles)
{
   boolean irq_occurred = FALSE;

   apu->apus.dmc.phaseacc_cur -= (int)cpu_cycles;
   while(apu->apus.dmc.phaseacc_cur < 0)
   {
      apu->apus.dmc.phaseacc_cur += apu->apus.dmc.freq_cur * 8;
      if (apu->apus.dmc.dma_length_cur)
      {
        if (--apu->apus.dmc.dma_length_cur == 0)
        {
           if (apu->apus.dmc.looping_cur)
           {
              apu->apus.dmc.dma_length_cur = apu->apus.dmc.cached_dmalength_cur;
              apu->apus.dmc.irq_occurred_cur = FALSE;
           }
           else
           {
              apu->apus.dmc.dma_length_cur = 0;
              if (apu->apus.dmc.irq_gen_cur)
              {
                 apu->apus.dmc.irq_occurred_cur = TRUE;
                 irq_occurred = TRUE;
              }
              apu->apus.dmc.enabled_cur = FALSE;
           }
        }
      }
   }
   return irq_occurred;
}

/*
** nes_apu.c,v
** Revision 1.4  2002/01/09 18:13:20  tekezo
** *** empty log message ***
**
** Revision 1.3  2002/01/06 07:31:28  tekezo
** *** empty log message ***
**
** Revision 1.2  2001/12/18 03:09:03  tekezo
** *** empty log message ***
**
** Revision 1.1  2001/12/11 05:43:07  tekezo
** *** empty log message ***
**
** Revision 1.10  2001/11/07 16:30:09  tekezo
** 4.0-beta
**
** Revision 1.9  2001/10/15 18:29:26  tekezo
** now work with -fno-stack-check (still buggy)
**
** Revision 1.8  2001/09/29 13:07:53  tekezo
** brushup
**
** Revision 1.7  2001/09/23 17:28:48  tekezo
** bug fix for gradius2
**
** Revision 1.6  2001/09/23 12:23:57  tekezo
** now support SNSS(real)
**
** Revision 1.5  2001/09/18 14:14:41  tekezo
** now works on CD-R
**
** Revision 2.16  2001/02/18 21:31:00  YANO, takashi
** added $4017:bit7 control
** fixed set chan->enabled
** fixed bug of DPCM last sample in APU_YANO
** trim channel balance again
** fixed APU_BASEFREQ
**
** Revision 2.15  2001/01/04 22:09:10  YANO, takashi
** fixed dmc bug of delta_bit
**
** Revision 2.14  2001/01/03 17:46:00  YANO, takashi
** fixed code for DC balance
** trim noise and dmc volume
**
** Revision 2.13  2000/12/23 02:00:40  YANO, takashi
** added apu_setmode()
**
** Revision 2.12  2000/12/22 23:23:40  YANO, takashi
** trim output volume balance
** re-disabled APU_IDEAL_TRIANGLE
** modify weighted filter
**
** Revision 2.11  2000/12/17 00:08:10  YANO, takashi
** cancel DC offset
** enable APU_IDEAL_TRIANGLE
**
** Revision 2.10  2000/12/12 02:07:46  YANO, takashi
** improve sound purity
**
** Revision 2.09  2000/12/09 11:41:00  TAKEDA, toshiya
** sync DPCM registers
** support DMCP IRQ
**
** Revision 2.08  2000/12/07 00:10:00  TAKEDA, toshiya
** sync DPCM registers
**
** Revision 2.07  2000/11/15 16:32:00  TAKEDA, toshiya
** fixed memory reak of ExtraSound
**
** Revision 2.06  2000/11/02 21:40:00  TAKEDA, toshiya
** fixed read $4015 (triangle.write_latency)
**
** Revision 2.05  2000/11/01 21:44:00  TAKEDA, toshiya
** fixed read $4015
**
** Revision 2.04  2000/10/26 00:05:00  TAKEDA, toshiya
** changed VRC6 volume
** changed chip number
**
** Revision 2.03  2000/10/23 16:06:00  TAKEDA, toshiya
** added ExtraSound Support of MMC5
** sync All ExtraSound
**
** Revision 2.02  2000/10/23 00:07:00  TAKEDA, toshiya
** fixed VRC6 write reg
**
** Revision 2.01  2000/10/22 21:12:00  TAKEDA, toshiya
** added ExtraSound Support of FME7
**
** Revision 2.00  2000/10/22 00:12:15  TAKEDA, toshiya
** added ExtraSound Support of N106, FDS, VRC6, VRC7
**
** ---------------------------------------------------
**
** Revision 1.33  2000/08/15 12:38:04  matt
** removed debug output
**
** Revision 1.32  2000/08/15 12:36:51  matt
** calling apu_process with buffer=NULL causes silent emulation of APU
**
** Revision 1.31  2000/08/11 02:27:21  matt
** general cleanups, plus apu_setparams routine
**
** Revision 1.30  2000/07/31 04:32:52  matt
** fragsize problem fixed, perhaps
**
** Revision 1.29  2000/07/30 04:32:59  matt
** no more apu_getcyclerate hack
**
** Revision 1.28  2000/07/28 03:15:46  matt
** accuracy changes for rectangle frequency sweeps
**
** Revision 1.27  2000/07/27 02:49:50  matt
** eccentricity in sweeping hardware now emulated correctly
**
** Revision 1.26  2000/07/25 02:25:14  matt
** safer apu_destroy
**
** Revision 1.25  2000/07/23 15:10:54  matt
** hacks for win32
**
** Revision 1.24  2000/07/17 01:52:31  matt
** made sure last line of all source files is a newline
**
** Revision 1.23  2000/07/10 19:24:55  matt
** irqs are not supported in NSF playing mode
**
** Revision 1.22  2000/07/10 13:54:32  matt
** using generic nes_irq() now
**
** Revision 1.21  2000/07/10 05:29:34  matt
** moved joypad/oam dma from apu to ppu
**
** Revision 1.20  2000/07/09 03:49:31  matt
** apu irqs now draw an irq line (bleh)
**
** Revision 1.19  2000/07/04 04:53:26  matt
** minor changes, sound amplification
**
** Revision 1.18  2000/07/03 02:18:53  matt
** much better external module exporting
**
** Revision 1.17  2000/06/26 11:01:55  matt
** made triangle a tad quieter
**
** Revision 1.16  2000/06/26 05:10:33  matt
** fixed cycle rate generation accuracy
**
** Revision 1.15  2000/06/26 05:00:37  matt
** cleanups
**
** Revision 1.14  2000/06/23 11:06:24  matt
** more faithful mixing of channels
**
** Revision 1.13  2000/06/23 03:29:27  matt
** cleaned up external sound inteface
**
** Revision 1.12  2000/06/20 00:08:39  matt
** bugfix to rectangle wave
**
** Revision 1.11  2000/06/13 13:48:58  matt
** fixed triangle write latency for fixed point apu cycle rate
**
** Revision 1.10  2000/06/12 01:14:36  matt
** minor change to clipping extents
**
** Revision 1.9  2000/06/09 20:00:56  matt
** fixed noise hiccup in NSF player mode
**
** Revision 1.8  2000/06/09 16:49:02  matt
** removed all floating point from sound generation
**
** Revision 1.7  2000/06/09 15:12:28  matt
** initial revision
**
*/
