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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    *priv ;
      double            src_ratio, input_index, rem ;
      int               ch ;

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

      priv = (ZOH_DATA*) psrc->private_data ;

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

      priv->in_count = data->input_frames * priv->channels ;
      priv->out_count = data->output_frames * priv->channels ;
      priv->in_used = priv->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 && priv->out_gen < priv->out_count)
      {
            if (priv->in_used + priv->channels * input_index >= priv->in_count)
                  break ;

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

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

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

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

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

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

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

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

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

      psrc->last_position = input_index ;

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

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

      data->input_frames_used = priv->in_used / priv->channels ;
      data->output_frames_gen = priv->out_gen / priv->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 *priv = NULL ;

      if (src_enum != SRC_ZERO_ORDER_HOLD)
            return SRC_ERR_BAD_CONVERTER ;

      if (psrc->private_data != NULL)
      {     free (psrc->private_data) ;
            psrc->private_data = NULL ;
            } ;

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

      priv->zoh_magic_marker = ZOH_MAGIC_MARKER ;
      priv->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 *priv ;

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

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

      return ;
} /* zoh_reset */


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