nes_apu.c

linux下的MPEG1

/*
** Nofrendo (c) 1998-2000 Matthew Conte ([e-mail])
**
**
** 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
** $Id: nes_apu.c,v 1.4 2005/05/07 09:11:39 valtri Exp $
*/

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

#ifdef NSF_PLAYER
#include "nsf.h"
#else
#include "nes.h"
#include "nes_ppu.h"
#include "nes_mmc.h"
#include "nesinput.h"
#endif /* !NSF_PLAYER */


#define  APU_OVERSAMPLE
#define  APU_VOLUME_DECAY(x)  ((x) -= ((x) >> 7))


/* 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 };

#if 0 /* unused */
static void apu_setcontext(apu_t *src_apu)
{
   apu = src_apu;
}
#endif

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

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];
}

void apu_setchan(int chan, boolean enabled)
{
   ASSERT(apu);
   apu->mix_enable[chan] = enabled;
}

/* 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
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

/* 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_OVERSAMPLE
   int num_times;
   int32 total;
#endif

   APU_VOLUME_DECAY(chan->output_vol);

   if (FALSE == chan->enabled || 0 == chan->vbl_length)
      return APU_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 ((FALSE == chan->sweep_inc && chan->freq > chan->freq_limit)
       || chan->freq < APU_TO_FIXED(4))
      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; /* 120/60 */
      while (chan->sweep_phase < 0)
      {
         chan->sweep_phase += chan->sweep_delay;
         if (chan->sweep_inc) /* ramp up */
            chan->freq -= chan->freq >> (chan->sweep_shifts);
         else /* ramp down */
            chan->freq += chan->freq >> (chan->sweep_shifts);
      }
   }

   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

   while (chan->phaseacc < 0)
   {
      chan->phaseacc += 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 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 >> 2))
static int32 apu_triangle(triangle_t *chan)
{
   APU_VOLUME_DECAY(chan->output_vol);

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

   if (chan->counter_started)
   {
      if (chan->linear_length > 0)
         chan->linear_length--;
      if (chan->vbl_length && FALSE == chan->holdnote)
         chan->vbl_length--;
   }
   else if (FALSE == chan->holdnote && chan->write_latency)
   {
      if (--chan->write_latency == 0)
         chan->counter_started = TRUE;
   }
/*
   if (chan->countmode == COUNTMODE_COUNT)
   {
      if (chan->linear_length > 0)
         chan->linear_length--;
      if (chan->vbl_length)
         chan->vbl_length--;
   }
*/
   if (0 == chan->linear_length || chan->freq < APU_TO_FIXED(4)) /* inaudible */
      return APU_TRIANGLE_OUTPUT;

   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);
   }

   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 + chan->output_vol) >> 2)

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

#if defined(APU_OVERSAMPLE) && defined(REALTIME_NOISE)
#else
   int32 noise_bit;
#endif
#ifdef APU_OVERSAMPLE
   int num_times;
   int32 total;
#endif

   APU_VOLUME_DECAY(chan->output_vol);

   if (FALSE == chan->enabled || 0 == chan->vbl_length)
      return APU_NOISE_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++;
   }

   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

   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
      noise_bit = shift_register15(chan->xor_tap);
#endif

#else
      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
#endif /* REALTIME_NOISE */
   }

#ifdef APU_OVERSAMPLE
   chan->output_vol = total / num_times;
#else
   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

   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 + chan->output_vol) >> 2)
static int32 apu_dmc(dmc_t *chan)
{
   int delta_bit;

   APU_VOLUME_DECAY(chan->output_vol);

   /* only process when channel is alive */
   if (chan->dma_length)
   {
      chan->phaseacc -= apu->cycle_rate; /* # of cycles per sample */
      
      while (chan->phaseacc < 0)
      {
         chan->phaseacc += chan->freq;
         
         delta_bit = (chan->dma_length & 7) ^ 7;
         
         if (7 == delta_bit)
         {
            chan->cur_byte = nes6502_getbyte(chan->address);
            
            /* steal a cycle from CPU*/
            nes6502_setdma(1);

            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;
                  nes6502_irq();
               }

               /* bodge for timestamp queue */
               chan->enabled = FALSE;
               break;
            }
         }

         /* positive delta */
         if (chan->cur_byte & (1 << delta_bit))
         {
            if (chan->regs[1] < 0x7D)
            {
               chan->regs[1] += 2;
               chan->output_vol += (2 << 8);
            }
/*
            if (chan->regs[1] < 0x3F)
               chan->regs[1]++;

            chan->output_vol &= ~(0x7E << 8);
            chan->output_vol |= ((chan->regs[1] << 1) << 8);
*/
         }
         /* negative delta */
         else            
         {
            if (chan->regs[1] > 1)
            {
               chan->regs[1] -= 2;
               chan->output_vol -= (2 << 8);
            }

/*
            if (chan->regs[1] > 0)
               chan->regs[1]--;

            chan->output_vol &= ~(0x7E << 8);
            chan->output_vol |= ((chan->regs[1] << 1) << 8);
*/
         }
      }
   }

   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->rectangle[chan].regs[0] = value;

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

   case APU_WRA1:
   case APU_WRB1: