Pico PCM, only one hardcoded mode for now

[picodrive.git] / Pico / Pico / xpcm.c

/*
 * The following ADPCM algorithm was stolen from MAME aica driver.
 * I'm quite sure it's not the right one, but it's the
 * best sounding of the ones that I tried.
 */

#include "../PicoInt.h"

#define ADPCMSHIFT      8
#define ADFIX(f)        (int) ((double)f * (double)(1<<ADPCMSHIFT))

/* limitter */
#define Limit(val, max, min) { \
	if ( val > max )      val = max; \
	else if ( val < min ) val = min; \
}

const int TableQuant[8] =
{
  ADFIX(0.8984375),
  ADFIX(0.8984375),
  ADFIX(0.8984375),
  ADFIX(0.8984375),
  ADFIX(1.19921875),
  ADFIX(1.59765625),
  ADFIX(2.0),
  ADFIX(2.3984375)
};

// changed using trial and error..
//const int quant_mul[16] = { 1, 3, 5, 7, 9, 11, 13, 15, -1, -3, -5, -7, -9, -11, -13, -15 };
const int quant_mul[16]   = { 1, 3, 5, 7, 9, 11, 13, -1, -1, -3, -5, -7, -9, -11, -13, -15 };

static int sample = 0, quant = 0;

PICO_INTERNAL void PicoPicoPCMReset(void)
{
  sample = 0;
  quant = 0x7f;
  memset(PicoPicohw.xpcm_buffer, 0, sizeof(PicoPicohw.xpcm_buffer));
}

#define XSHIFT 7

#define do_sample() \
{ \
  sample += quant * quant_mul[srcval] >> XSHIFT; \
  quant = (quant * TableQuant[srcval&7]) >> ADPCMSHIFT; \
  Limit(quant, 0x6000, 0x7f); \
  Limit(sample, 32767, -32768); \
}

PICO_INTERNAL void PicoPicoPCMUpdate(short *buffer, int length, int stereo)
{
  unsigned char *src = PicoPicohw.xpcm_buffer;
  unsigned char *lim = PicoPicohw.xpcm_ptr;
  int srcval, stepsamples = (44100<<10)/16000, needsamples = 0; // TODO: stepsamples

  if (src == lim)
  {
    if (stereo)
      // still must expand SN76496 to stereo
      for (; length > 0; buffer+=2, length--)
        buffer[1] = buffer[0];
    sample = quant = 0;
    return;
  }

  for (; length > 0 && src < lim; src++)
  {
    srcval = *src >> 4;
    do_sample();

    for (needsamples += stepsamples; needsamples > (1<<10) && length > 0; needsamples -= (1<<10), length--) {
      *buffer++ = sample;
      if (stereo) { buffer[0] = buffer[-1]; buffer++; }
    }

    srcval = *src & 0xf;
    do_sample();

    for (needsamples += stepsamples; needsamples > (1<<10) && length > 0; needsamples -= (1<<10), length--) {
      *buffer++ = sample;
      if (stereo) { buffer[0] = buffer[-1]; buffer++; }
    }
  }

  if (src < lim) {
    int di = lim - src;
    memmove(PicoPicohw.xpcm_buffer, src, di);
    PicoPicohw.xpcm_ptr = PicoPicohw.xpcm_buffer + di;
    elprintf(EL_STATUS, "xpcm update: over %i", di);
  }
  else
  {
    elprintf(EL_STATUS, "xpcm update: under %i", length);
    PicoPicohw.xpcm_ptr = PicoPicohw.xpcm_buffer;
  }
}