Genesis-Plus-GX/source/sound/sound.c

/***************************************************************************************
 *  Genesis Plus 1.2a
 *
 *  Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003  Charles Mac Donald (original code)
 *  modified by Eke-Eke (compatibility fixes & additional code), GC/Wii port
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  Sound Hardware
 ****************************************************************************************/

#include "shared.h"

#define CLOCK_NTSC 53693175
#define CLOCK_PAL  53203424

/* generic functions */
int  (*_YM2612_Write)(unsigned char adr, unsigned char data);
int  (*_YM2612_Read)(void);
void (*_YM2612_Update)(int **buf, int length);
int (*_YM2612_Reset)(void);

/* cycle-accurate samples */
static int m68cycles_per_sample[2];

/* pointer to current SRC buffer */
float *src_buffer;

/* YM2612 register arrays */
int fm_reg[2][0x100];

/* return the number of samples that should have been rendered so far */
static inline uint32 fm_sample_cnt(uint8 is_z80)
{
  if (is_z80) return ((count_z80 + current_z80 - z80_ICount) * 15) / (7 * m68cycles_per_sample[0]);
  else return count_m68k / m68cycles_per_sample[0];
}

static inline uint32 psg_sample_cnt(uint8 is_z80)
{
  if (is_z80) return ((count_z80 + current_z80 - z80_ICount) * 15) / (7 * m68cycles_per_sample[1]);
  else return count_m68k / m68cycles_per_sample[1];
}

/* update FM samples */
static inline void fm_update()
{
  if(snd.fm.curStage - snd.fm.lastStage > 0)
  {
    int *tempBuffer[2];
    tempBuffer[0] = snd.fm.buffer[0] + snd.fm.lastStage;
    tempBuffer[1] = snd.fm.buffer[1] + snd.fm.lastStage;

    if (src_buffer)
    {
      src_buffer = src_data.data_in + (snd.fm.lastStage * 2);
    }

    _YM2612_Update(tempBuffer, snd.fm.curStage - snd.fm.lastStage);
    snd.fm.lastStage = snd.fm.curStage;
  }
}

/* update PSG samples */
static inline void psg_update()
{
  if(snd.psg.curStage - snd.psg.lastStage > 0)
  {
    int16 *tempBuffer = snd.psg.buffer + snd.psg.lastStage;
    SN76489_Update (0, tempBuffer, snd.psg.curStage - snd.psg.lastStage);
    snd.psg.lastStage = snd.psg.curStage;
  }
}

void sound_init(int rate)
{
  double vclk = (vdp_pal ? (double)CLOCK_PAL : (double)CLOCK_NTSC) / 7.0;  /* 68000 and YM2612 clock */
  double zclk = (vdp_pal ? (double)CLOCK_PAL : (double)CLOCK_NTSC) / 15.0; /* Z80 and SN76489 clock  */

  /* cycle-accurate samples */
  m68cycles_per_sample[0] = (m68cycles_per_line * lines_per_frame * vdp_rate) / rate;
  m68cycles_per_sample[1] = (m68cycles_per_line * lines_per_frame * vdp_rate) / rate;

  /* YM2612 is emulated at the original frequency */
  src_buffer = 0;
  if (src_data.data_in)
  {
    /* YM2612 original frequency is VCLK/144 */
    m68cycles_per_sample[0] = 144;

    /* Initialize SRC buffer */
    src_buffer = src_data.data_in;
  }

  /* initialize sound chips */
  SN76489_Init(0, (int)zclk, rate);
  SN76489_Config(0, MUTE_ALLON, VOL_FULL, FB_SEGAVDP, SRW_SEGAVDP, 0);

  if (config.fm_core)
  {
    _YM2612_Write  = YM2612_Write;
    _YM2612_Read   = YM2612_Read;
    _YM2612_Update = YM2612_Update;
    _YM2612_Reset  = YM2612_Reset;
    YM2612_Init((int)vclk, rate, config.hq_fm);
  }
  else
  {
    _YM2612_Write  = YM2612Write;
    _YM2612_Read   = YM2612Read;
    _YM2612_Update = YM2612UpdateOne;
    _YM2612_Reset  = YM2612ResetChip;
    YM2612Init ((int)vclk, rate);
  }
} 

void sound_update(void)
{
  /* finalize sound buffers */
  snd.fm.curStage  = (src_data.data_in) ? src_data.input_frames : snd.buffer_size;
  snd.psg.curStage = snd.buffer_size;

  /* update last samples (if needed) */
  fm_update();
  psg_update();

  /* Resampling */
  if (src_data.data_in)
  {
    /* samplerate conversion */
    src_simple (&src_data, (config.hq_fm&1) ? SRC_LINEAR : SRC_SINC_FASTEST, 2);

    /* this is basically libsamplerate "src_float_to_int_array" function, adapted to interlace samples */
    double scaled_value;
    int len = snd.buffer_size;
    while (len)
    {
      len -- ;
      scaled_value = src_data.data_out[len*2] * (8.0 * 0x10000000);
      if (scaled_value >= (1.0 * 0x7FFFFFFF))
        snd.fm.buffer[0][len] = 0x7fffffff;
      else if (scaled_value <= (-8.0 * 0x10000000))
        snd.fm.buffer[0][len] = -1 - 0x7fffffff;
      else
        snd.fm.buffer[0][len] = lrint(scaled_value);

      scaled_value = src_data.data_out[len*2+1] * (8.0 * 0x10000000);
      if (scaled_value >= (1.0 * 0x7FFFFFFF))
        snd.fm.buffer[1][len] = 0x7fffffff;
      else if (scaled_value <= (-8.0 * 0x10000000))
        snd.fm.buffer[1][len] = -1 - 0x7fffffff;
      else
        snd.fm.buffer[1][len] = lrint(scaled_value);
    }
  }

  /* reset samples count */
  snd.fm.curStage   = 0;
  snd.fm.lastStage  = 0;
  snd.psg.curStage  = 0;
  snd.psg.lastStage = 0;
}

/* YM2612 control */
/* restore FM registers */
void fm_restore(void)
{
  int i;

  _YM2612_Reset();

  /* feed all the registers and update internal state */
  for(i = 0; i < 0x100; i++)
  {
    _YM2612_Write(0, i);
    _YM2612_Write(1, fm_reg[0][i]);
    _YM2612_Write(2, i);
    _YM2612_Write(3, fm_reg[1][i]);
  }
}

/* write FM chip */
void fm_write(unsigned int cpu, unsigned int address, unsigned int data)
{
  if (address & 1)
  {
    snd.fm.curStage = fm_sample_cnt(cpu);
    fm_update();
  }
  _YM2612_Write(address & 3, data);
}

/* read FM status */
unsigned int fm_read(unsigned int cpu, unsigned int address)
{
  snd.fm.curStage = fm_sample_cnt(cpu);
  fm_update();
  return (_YM2612_Read() & 0xff);
}


/* PSG write */
void psg_write(unsigned int cpu, unsigned int data)
{
  snd.psg.curStage = psg_sample_cnt(cpu);
  psg_update();
  SN76489_Write(0, data);
}