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

/*
** Copyright (C) 2002-2008 Erik de Castro Lopo <erikd@mega-nerd.com>
**
** 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.
*/

/*
** This code is part of Secret Rabibt Code aka libsamplerate. A commercial
** use license for this code is available, please see:
**    http://www.mega-nerd.com/SRC/procedure.html
*/

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

#include "config.h"
#include "float_cast.h"
#include "common.h"

static int zoh_vari_process (SRC_PRIVATE *psrc, SRC_DATA *data) ;
static void zoh_reset (SRC_PRIVATE *psrc) ;

/*========================================================================================
*/

#define  ZOH_MAGIC_MARKER  MAKE_MAGIC ('s', 'r', 'c', 'z', 'o', 'h')

typedef struct
{  int    zoh_magic_marker ;
  int    channels ;
  int    reset ;
  long  in_count, in_used ;
  long  out_count, out_gen ;
  float  last_value [1] ;
} ZOH_DATA ;

/*----------------------------------------------------------------------------------------
*/

static int
zoh_vari_process (SRC_PRIVATE *psrc, SRC_DATA *data)
{  ZOH_DATA   *zoh ;
  double    src_ratio, input_index, rem ;
  int      ch ;

  if (psrc->private_data == NULL)
    return SRC_ERR_NO_PRIVATE ;

  zoh = (ZOH_DATA*) psrc->private_data ;

  if (zoh->reset)
  {  /* If we have just been reset, set the last_value data. */
    for (ch = 0 ; ch < zoh->channels ; ch++)
      zoh->last_value [ch] = data->data_in [ch] ;
    zoh->reset = 0 ;
    } ;

  zoh->in_count = data->input_frames * zoh->channels ;
  zoh->out_count = data->output_frames * zoh->channels ;
  zoh->in_used = zoh->out_gen = 0 ;

  src_ratio = psrc->last_ratio ;
  input_index = psrc->last_position ;

  /* Calculate samples before first sample in input array. */
  while (input_index < 1.0 && zoh->out_gen < zoh->out_count)
  {
    if (zoh->in_used + zoh->channels * input_index >= zoh->in_count)
      break ;

    if (zoh->out_count > 0 && fabs (psrc->last_ratio - data->src_ratio) > SRC_MIN_RATIO_DIFF)
      src_ratio = psrc->last_ratio + zoh->out_gen * (data->src_ratio - psrc->last_ratio) / zoh->out_count ;

    for (ch = 0 ; ch < zoh->channels ; ch++)
    {  data->data_out [zoh->out_gen] = zoh->last_value [ch] ;
      zoh->out_gen ++ ;
      } ;

    /* Figure out the next index. */
    input_index += 1.0 / src_ratio ;
    } ;

  rem = fmod_one (input_index) ;
  zoh->in_used += zoh->channels * lrint (input_index - rem) ;
  input_index = rem ;

  /* Main processing loop. */
  while (zoh->out_gen < zoh->out_count && zoh->in_used + zoh->channels * input_index <= zoh->in_count)
  {
    if (zoh->out_count > 0 && fabs (psrc->last_ratio - data->src_ratio) > SRC_MIN_RATIO_DIFF)
      src_ratio = psrc->last_ratio + zoh->out_gen * (data->src_ratio - psrc->last_ratio) / zoh->out_count ;

    for (ch = 0 ; ch < zoh->channels ; ch++)
    {  data->data_out [zoh->out_gen] = data->data_in [zoh->in_used - zoh->channels + ch] ;
      zoh->out_gen ++ ;
      } ;

    /* Figure out the next index. */
    input_index += 1.0 / src_ratio ;
    rem = fmod_one (input_index) ;

    zoh->in_used += zoh->channels * lrint (input_index - rem) ;
    input_index = rem ;
    } ;

  if (zoh->in_used > zoh->in_count)
  {  input_index += (zoh->in_used - zoh->in_count) / zoh->channels ;
    zoh->in_used = zoh->in_count ;
    } ;

  psrc->last_position = input_index ;

  if (zoh->in_used > 0)
    for (ch = 0 ; ch < zoh->channels ; ch++)
      zoh->last_value [ch] = data->data_in [zoh->in_used - zoh->channels + ch] ;

  /* Save current ratio rather then target ratio. */
  psrc->last_ratio = src_ratio ;

  data->input_frames_used = zoh->in_used / zoh->channels ;
  data->output_frames_gen = zoh->out_gen / zoh->channels ;

  return SRC_ERR_NO_ERROR ;
} /* zoh_vari_process */

/*------------------------------------------------------------------------------
*/

const char*
zoh_get_name (int src_enum)
{
  if (src_enum == SRC_ZERO_ORDER_HOLD)
    return "ZOH Interpolator" ;

  return NULL ;
} /* zoh_get_name */

const char*
zoh_get_description (int src_enum)
{
  if (src_enum == SRC_ZERO_ORDER_HOLD)
    return "Zero order hold interpolator, very fast, poor quality." ;

  return NULL ;
} /* zoh_get_descrition */

int
zoh_set_converter (SRC_PRIVATE *psrc, int src_enum)
{  ZOH_DATA *zoh = NULL ;

  if (src_enum != SRC_ZERO_ORDER_HOLD)
    return SRC_ERR_BAD_CONVERTER ;

  if (psrc->private_data != NULL)
  {  zoh = (ZOH_DATA*) psrc->private_data ;
    if (zoh->zoh_magic_marker != ZOH_MAGIC_MARKER)
    {  free (psrc->private_data) ;
      psrc->private_data = NULL ;
      } ;
    } ;

  if (psrc->private_data == NULL)
  {  zoh = calloc (1, sizeof (*zoh) + psrc->channels * sizeof (float)) ;
    if (zoh == NULL)
      return SRC_ERR_MALLOC_FAILED ;
    psrc->private_data = zoh ;
    } ;

  zoh->zoh_magic_marker = ZOH_MAGIC_MARKER ;
  zoh->channels = psrc->channels ;

  psrc->const_process = zoh_vari_process ;
  psrc->vari_process = zoh_vari_process ;
  psrc->reset = zoh_reset ;

  zoh_reset (psrc) ;

  return SRC_ERR_NO_ERROR ;
} /* zoh_set_converter */

/*===================================================================================
*/

static void
zoh_reset (SRC_PRIVATE *psrc)
{  ZOH_DATA *zoh ;

  zoh = (ZOH_DATA*) psrc->private_data ;
  if (zoh == NULL)
    return ;

  zoh->channels = psrc->channels ;
  zoh->reset = 1 ;
  memset (zoh->last_value, 0, sizeof (zoh->last_value [0]) * zoh->channels) ;

  return ;
} /* zoh_reset */