src_zoh.c

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/*
** Copyright (C) 2002-2011 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 Rabbit 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 (data->input_frames <= 0)
        return SRC_ERR_NO_ERROR ;

    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 */