resample.c

SDL_mixer 是一个基于 SDL 的混音器

/*

    TiMidity -- Experimental MIDI to WAVE converter
    Copyright (C) 1995 Tuukka Toivonen <[e-mail]>

    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., 675 Mass Ave, Cambridge, MA 02139, USA.

    resample.c
*/

#include <math.h>
#include <stdio.h>
#include <stdlib.h>

#include "config.h"
#include "common.h"
#include "instrum.h"
#include "playmidi.h"
#include "output.h"
#include "ctrlmode.h"
#include "tables.h"
#include "resample.h"

#ifdef LINEAR_INTERPOLATION
# if defined(LOOKUP_HACK) && defined(LOOKUP_INTERPOLATION)
#   define RESAMPLATION \
       v1=src[ofs>>FRACTION_BITS];\
       v2=src[(ofs>>FRACTION_BITS)+1];\
       *dest++ = (resample_t)(v1 + (iplookup[(((v2-v1)<<5) & 0x03FE0) | \
           ((ofs & FRACTION_MASK) >> (FRACTION_BITS-5))]));
# else
#   define RESAMPLATION \
      v1=src[ofs>>FRACTION_BITS];\
      v2=src[(ofs>>FRACTION_BITS)+1];\
      *dest++ = (resample_t)(v1 + (((v2-v1) * (ofs & FRACTION_MASK)) >> FRACTION_BITS));
# endif
#  define INTERPVARS sample_t v1, v2
#else
/* Earplugs recommended for maximum listening enjoyment */
#  define RESAMPLATION *dest++ = src[ofs>>FRACTION_BITS];
#  define INTERPVARS
#endif

#define FINALINTERP if (ofs == le) *dest++=src[ofs>>FRACTION_BITS];
/* So it isn't interpolation. At least it's final. */

extern resample_t *resample_buffer;

/*************** resampling with fixed increment *****************/

static resample_t *rs_plain(int v, int32 *countptr)
{

  /* Play sample until end, then free the voice. */

  INTERPVARS;
  Voice 
    *vp=&voice[v];
  resample_t 
    *dest=resample_buffer;
  sample_t 
    *src=vp->sample->data;
  int32 
    ofs=vp->sample_offset,
    incr=vp->sample_increment,
    le=vp->sample->data_length,
    count=*countptr;

#ifdef PRECALC_LOOPS
  int32 i, j;

  if (incr<0) incr = -incr; /* In case we're coming out of a bidir loop */

  /* Precalc how many times we should go through the loop.
     NOTE: Assumes that incr > 0 and that ofs <= le */
  i = (le - ofs) / incr + 1;

  if (i > count)
    {
      i = count;
      count = 0;
    } 
  else count -= i;

  for(j = 0; j < i; j++)
    {
      RESAMPLATION;
      ofs += incr;
    }

  if (ofs >= le) 
    {
      FINALINTERP;
      vp->status=VOICE_FREE;
      ctl->note(v);
      *countptr-=count+1;
    }

#else /* PRECALC_LOOPS */
    while (count--)
    {
      RESAMPLATION;
      ofs += incr;
      if (ofs >= le)
	{
	  FINALINTERP;
	  vp->status=VOICE_FREE;
 	  ctl->note(v);
	  *countptr-=count+1;
	  break;
	}
    }
#endif /* PRECALC_LOOPS */
  
  vp->sample_offset=ofs; /* Update offset */
  return resample_buffer;
}

static resample_t *rs_loop(Voice *vp, int32 count)
{

  /* Play sample until end-of-loop, skip back and continue. */

  INTERPVARS;
  int32 
    ofs=vp->sample_offset, 
    incr=vp->sample_increment,
    le=vp->sample->loop_end, 
    ll=le - vp->sample->loop_start;
  resample_t
    *dest=resample_buffer;
  sample_t
    *src=vp->sample->data;

#ifdef PRECALC_LOOPS
  int32 i;
 
  if (ofs < 0 || le < 0) return resample_buffer;

  while (count) 
    {
      if (ofs >= le)
	/* NOTE: Assumes that ll > incr and that incr > 0. */
	ofs -= ll;
      /* Precalc how many times we should go through the loop */
      i = (le - ofs) / incr + 1;
      if (i > count) 
	{
	  i = count;
	  count = 0;
	} 
      else count -= i;
      if (i > 0)
      while (i--) 
	{
	  RESAMPLATION;
	  ofs += incr;
	}
    }
#else
  while (count--)
    {
      RESAMPLATION;
      ofs += incr;
      if (ofs>=le)
	ofs -= ll; /* Hopefully the loop is longer than an increment. */
    }
#endif

  vp->sample_offset=ofs; /* Update offset */
  return resample_buffer;
}

static resample_t *rs_bidir(Voice *vp, int32 count)
{
  INTERPVARS;
  int32 
    ofs=vp->sample_offset,
    incr=vp->sample_increment,
    le=vp->sample->loop_end,
    ls=vp->sample->loop_start;
  resample_t 
    *dest=resample_buffer; 
  sample_t 
    *src=vp->sample->data;

#ifdef PRECALC_LOOPS
  int32
    le2 = le<<1, 
    ls2 = ls<<1,
    i;
  /* Play normally until inside the loop region */

  if (ofs <= ls) 
    {
      /* NOTE: Assumes that incr > 0, which is NOT always the case
	 when doing bidirectional looping.  I have yet to see a case
	 where both ofs <= ls AND incr < 0, however. */
      i = (ls - ofs) / incr + 1;
      if (i > count) 
	{
	  i = count;
	  count = 0;
	} 
      else count -= i;
      while (i--) 
	{
	  RESAMPLATION;
	  ofs += incr;
	}
    }

  /* Then do the bidirectional looping */
  
  while(count) 
    {
      /* Precalc how many times we should go through the loop */
      i = ((incr > 0 ? le : ls) - ofs) / incr + 1;
      if (i > count) 
	{
	  i = count;
	  count = 0;
	} 
      else count -= i;
      while (i--) 
	{
	  RESAMPLATION;
	  ofs += incr;
	}
      if (ofs>=le) 
	{
	  /* fold the overshoot back in */
	  ofs = le2 - ofs;
	  incr *= -1;
	} 
      else if (ofs <= ls) 
	{
	  ofs = ls2 - ofs;
	  incr *= -1;
	}
    }

#else /* PRECALC_LOOPS */
  /* Play normally until inside the loop region */

  if (ofs < ls)
    {
      while (count--)
	{
	  RESAMPLATION;
	  ofs += incr;
	  if (ofs>=ls)
	    break;
	}
    }

  /* Then do the bidirectional looping */

  if (count>0)
    while (count--)
      {
	RESAMPLATION;
	ofs += incr;
	if (ofs>=le)
	  {
	    /* fold the overshoot back in */
	    ofs = le - (ofs - le);
	    incr = -incr;
	  }
	else if (ofs <= ls)
	  {
	    ofs = ls + (ls - ofs);
	    incr = -incr;
	  }
      }  
#endif /* PRECALC_LOOPS */
  vp->sample_increment=incr;
  vp->sample_offset=ofs; /* Update offset */
  return resample_buffer;
}

/*********************** vibrato versions ***************************/

/* We only need to compute one half of the vibrato sine cycle */
static int vib_phase_to_inc_ptr(int phase)
{
  if (phase < VIBRATO_SAMPLE_INCREMENTS/2)
    return VIBRATO_SAMPLE_INCREMENTS/2-1-phase;
  else if (phase >= 3*VIBRATO_SAMPLE_INCREMENTS/2)
    return 5*VIBRATO_SAMPLE_INCREMENTS/2-1-phase;
  else
    return phase-VIBRATO_SAMPLE_INCREMENTS/2;
}

static int32 update_vibrato(Voice *vp, int sign)
{
  int32 depth;
  int phase, pb;
  double a;

  if (vp->vibrato_phase++ >= 2*VIBRATO_SAMPLE_INCREMENTS-1)
    vp->vibrato_phase=0;
  phase=vib_phase_to_inc_ptr(vp->vibrato_phase);
  
  if (vp->vibrato_sample_increment[phase])
    {
      if (sign)
	return -vp->vibrato_sample_increment[phase];
      else
	return vp->vibrato_sample_increment[phase];
    }

  /* Need to compute this sample increment. */
    
  depth=vp->sample->vibrato_depth<<7;

  if (vp->vibrato_sweep)
    {
      /* Need to update sweep */
      vp->vibrato_sweep_position += vp->vibrato_sweep;
      if (vp->vibrato_sweep_position >= (1<<SWEEP_SHIFT))
	vp->vibrato_sweep=0;
      else
	{
	  /* Adjust depth */
	  depth *= vp->vibrato_sweep_position;
	  depth >>= SWEEP_SHIFT;
	}
    }

  a = FSCALE(((double)(vp->sample->sample_rate) *
	      (double)(vp->frequency)) /
	     ((double)(vp->sample->root_freq) *
	      (double)(play_mode->rate)),
	     FRACTION_BITS);

  pb=(int)((sine(vp->vibrato_phase * 
		 (SINE_CYCLE_LENGTH/(2*VIBRATO_SAMPLE_INCREMENTS)))
	    * (double)(depth) * VIBRATO_AMPLITUDE_TUNING));

  if (pb<0)
    {
      pb=-pb;
      a /= bend_fine[(pb>>5) & 0xFF] * bend_coarse[pb>>13];
    }
  else
    a *= bend_fine[(pb>>5) & 0xFF] * bend_coarse[pb>>13];
  
  /* If the sweep's over, we can store the newly computed sample_increment */
  if (!vp->vibrato_sweep)
    vp->vibrato_sample_increment[phase]=(int32) a;

  if (sign)
    a = -a; /* need to preserve the loop direction */

  return (int32) a;
}

static resample_t *rs_vib_plain(int v, int32 *countptr)
{

  /* Play sample until end, then free the voice. */