ref: 1659c805af745f87d0baae19a3e54b9628c10c7a
dir: /src/src_sinc.c/
/*
** Copyright (C) 2002-2006 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"
#define SINC_MAGIC_MARKER MAKE_MAGIC (' ', 's', 'i', 'n', 'c', ' ')
/*========================================================================================
** Macros for handling the index into the array for the filter.
** Double precision floating point is not accurate enough so use a 64 bit
** fixed point value instead. SHIFT_BITS (current value of 48) is the number
** of bits to the right of the decimal point.
** The rest of the macros are for retrieving the fractional and integer parts
** and for converting floats and ints to the fixed point format or from the
** fixed point type back to integers and floats.
*/
#define MAKE_INCREMENT_T(x) ((increment_t) (x))
#define SHIFT_BITS 16
#define FP_ONE ((double) (((increment_t) 1) << SHIFT_BITS))
#define DOUBLE_TO_FP(x) (lrint ((x) * FP_ONE))
#define INT_TO_FP(x) (((increment_t) (x)) << SHIFT_BITS)
#define FP_FRACTION_PART(x) ((x) & ((((increment_t) 1) << SHIFT_BITS) - 1))
#define FP_INTEGER_PART(x) ((x) & (((increment_t) -1) << SHIFT_BITS))
#define FP_TO_INT(x) (((x) >> SHIFT_BITS))
#define FP_TO_DOUBLE(x) (FP_FRACTION_PART (x) / FP_ONE)
/*========================================================================================
*/
typedef int32_t increment_t ;
typedef float coeff_t ;
typedef struct
{ int sinc_magic_marker ;
int channels ;
long in_count, in_used ;
long out_count, out_gen ;
int coeff_half_len, index_inc ;
int has_diffs ;
double src_ratio, input_index ;
int coeff_len ;
coeff_t const *coeffs ;
int b_current, b_end, b_real_end, b_len ;
float buffer [1] ;
} SINC_FILTER ;
static int sinc_vari_process (SRC_PRIVATE *psrc, SRC_DATA *data) ;
static double calc_output (SINC_FILTER *filter, increment_t increment, increment_t start_filter_index, int ch) ;
static void prepare_data (SINC_FILTER *filter, SRC_DATA *data, int half_filter_chan_len) ;
static void sinc_reset (SRC_PRIVATE *psrc) ;
static coeff_t const high_qual_coeffs [] =
{
#include "high_qual_coeffs.h"
} ; /* high_qual_coeffs */
static coeff_t const mid_qual_coeffs [] =
{
#include "mid_qual_coeffs.h"
} ; /* mid_qual_coeffs */
static coeff_t const fastest_coeffs [] =
{
#include "fastest_coeffs.h"
} ; /* fastest_coeffs */
/*----------------------------------------------------------------------------------------
*/
const char*
sinc_get_name (int src_enum)
{
switch (src_enum)
{ case SRC_SINC_BEST_QUALITY :
return "Best Sinc Interpolator" ;
case SRC_SINC_MEDIUM_QUALITY :
return "Medium Sinc Interpolator" ;
case SRC_SINC_FASTEST :
return "Fastest Sinc Interpolator" ;
} ;
return NULL ;
} /* sinc_get_descrition */
const char*
sinc_get_description (int src_enum)
{
switch (src_enum)
{ case SRC_SINC_BEST_QUALITY :
return "Band limited sinc interpolation, best quality, 97dB SNR, 96% BW." ;
case SRC_SINC_MEDIUM_QUALITY :
return "Band limited sinc interpolation, medium quality, 97dB SNR, 90% BW." ;
case SRC_SINC_FASTEST :
return "Band limited sinc interpolation, fastest, 97dB SNR, 80% BW." ;
} ;
return NULL ;
} /* sinc_get_descrition */
int
sinc_set_converter (SRC_PRIVATE *psrc, int src_enum)
{ SINC_FILTER *filter, temp_filter ;
int count, bits ;
/* Quick sanity check. */
if (SHIFT_BITS >= sizeof (increment_t) * 8 - 1)
return SRC_ERR_SHIFT_BITS ;
if (psrc->private_data != NULL)
{ filter = (SINC_FILTER*) psrc->private_data ;
if (filter->sinc_magic_marker != SINC_MAGIC_MARKER)
{ free (psrc->private_data) ;
psrc->private_data = NULL ;
} ;
} ;
memset (&temp_filter, 0, sizeof (temp_filter)) ;
temp_filter.sinc_magic_marker = SINC_MAGIC_MARKER ;
temp_filter.channels = psrc->channels ;
psrc->const_process = sinc_vari_process ;
psrc->vari_process = sinc_vari_process ;
psrc->reset = sinc_reset ;
switch (src_enum)
{ case SRC_SINC_BEST_QUALITY :
temp_filter.coeffs = high_qual_coeffs ;
temp_filter.coeff_half_len = ARRAY_LEN (high_qual_coeffs) - 1 ;
temp_filter.index_inc = 128 ;
temp_filter.has_diffs = SRC_FALSE ;
temp_filter.coeff_len = ARRAY_LEN (high_qual_coeffs) ;
break ;
case SRC_SINC_MEDIUM_QUALITY :
temp_filter.coeffs = mid_qual_coeffs ;
temp_filter.coeff_half_len = ARRAY_LEN (mid_qual_coeffs) - 1 ;
temp_filter.index_inc = 128 ;
temp_filter.has_diffs = SRC_FALSE ;
temp_filter.coeff_len = ARRAY_LEN (mid_qual_coeffs) ;
break ;
case SRC_SINC_FASTEST :
temp_filter.coeffs = fastest_coeffs ;
temp_filter.coeff_half_len = ARRAY_LEN (fastest_coeffs) - 1 ;
temp_filter.index_inc = 128 ;
temp_filter.has_diffs = SRC_FALSE ;
temp_filter.coeff_len = ARRAY_LEN (fastest_coeffs) ;
break ;
default :
return SRC_ERR_BAD_CONVERTER ;
} ;
/*
** FIXME : This needs to be looked at more closely to see if there is
** a better way. Need to look at prepare_data () at the same time.
*/
temp_filter.b_len = 1000 + 2 * lrint (0.5 + temp_filter.coeff_len / (temp_filter.index_inc * 1.0) * SRC_MAX_RATIO) ;
temp_filter.b_len = MIN (temp_filter.b_len, 2048) ;
temp_filter.b_len *= temp_filter.channels ;
if ((filter = calloc (1, sizeof (SINC_FILTER) + sizeof (filter->buffer [0]) * (temp_filter.b_len + temp_filter.channels))) == NULL)
return SRC_ERR_MALLOC_FAILED ;
*filter = temp_filter ;
memset (&temp_filter, 0xEE, sizeof (temp_filter)) ;
psrc->private_data = filter ;
sinc_reset (psrc) ;
count = filter->coeff_half_len ;
for (bits = 0 ; (1 << bits) < count ; bits++)
count |= (1 << bits) ;
if (bits + SHIFT_BITS - 1 >= (int) (sizeof (increment_t) * 8))
return SRC_ERR_FILTER_LEN ;
return SRC_ERR_NO_ERROR ;
} /* sinc_set_converter */
static void
sinc_reset (SRC_PRIVATE *psrc)
{ SINC_FILTER *filter ;
filter = (SINC_FILTER*) psrc->private_data ;
if (filter == NULL)
return ;
filter->b_current = filter->b_end = 0 ;
filter->b_real_end = -1 ;
filter->src_ratio = filter->input_index = 0.0 ;
memset (filter->buffer, 0, filter->b_len * sizeof (filter->buffer [0])) ;
/* Set this for a sanity check */
memset (filter->buffer + filter->b_len, 0xAA, filter->channels * sizeof (filter->buffer [0])) ;
} /* sinc_reset */
/*========================================================================================
** Beware all ye who dare pass this point. There be dragons here.
*/
static int
sinc_vari_process (SRC_PRIVATE *psrc, SRC_DATA *data)
{ SINC_FILTER *filter ;
double input_index, src_ratio, count, float_increment, terminate, rem ;
increment_t increment, start_filter_index ;
int half_filter_chan_len, samples_in_hand, ch ;
if (psrc->private_data == NULL)
return SRC_ERR_NO_PRIVATE ;
filter = (SINC_FILTER*) psrc->private_data ;
/* If there is not a problem, this will be optimised out. */
if (sizeof (filter->buffer [0]) != sizeof (data->data_in [0]))
return SRC_ERR_SIZE_INCOMPATIBILITY ;
filter->in_count = data->input_frames * filter->channels ;
filter->out_count = data->output_frames * filter->channels ;
filter->in_used = filter->out_gen = 0 ;
src_ratio = psrc->last_ratio ;
/* Check the sample rate ratio wrt the buffer len. */
count = (filter->coeff_half_len + 2.0) / filter->index_inc ;
if (MIN (psrc->last_ratio, data->src_ratio) < 1.0)
count /= MIN (psrc->last_ratio, data->src_ratio) ;
/* Maximum coefficientson either side of center point. */
half_filter_chan_len = filter->channels * (lrint (count) + 1) ;
input_index = psrc->last_position ;
float_increment = filter->index_inc ;
rem = fmod (input_index, 1.0) ;
filter->b_current = (filter->b_current + filter->channels * lrint (input_index - rem)) % filter->b_len ;
input_index = rem ;
terminate = 1.0 / src_ratio + 1e-20 ;
/* Main processing loop. */
while (filter->out_gen < filter->out_count)
{
/* Need to reload buffer? */
samples_in_hand = (filter->b_end - filter->b_current + filter->b_len) % filter->b_len ;
if (samples_in_hand <= half_filter_chan_len)
{ prepare_data (filter, data, half_filter_chan_len) ;
samples_in_hand = (filter->b_end - filter->b_current + filter->b_len) % filter->b_len ;
if (samples_in_hand <= half_filter_chan_len)
break ;
} ;
/* This is the termination condition. */
if (filter->b_real_end >= 0)
{ if (filter->b_current + input_index + terminate >= filter->b_real_end)
break ;
} ;
if (fabs (psrc->last_ratio - data->src_ratio) > 1e-10)
src_ratio = psrc->last_ratio + filter->out_gen * (data->src_ratio - psrc->last_ratio) / (filter->out_count - 1) ;
float_increment = filter->index_inc * 1.0 ;
if (src_ratio < 1.0)
float_increment = filter->index_inc * src_ratio ;
increment = DOUBLE_TO_FP (float_increment) ;
start_filter_index = DOUBLE_TO_FP (input_index * float_increment) ;
for (ch = 0 ; ch < filter->channels ; ch++)
{ data->data_out [filter->out_gen] = (float_increment / filter->index_inc) *
calc_output (filter, increment, start_filter_index, ch) ;
filter->out_gen ++ ;
} ;
/* Figure out the next index. */
input_index += 1.0 / src_ratio ;
rem = fmod (input_index, 1.0) ;
filter->b_current = (filter->b_current + filter->channels * lrint (input_index - rem)) % filter->b_len ;
input_index = rem ;
} ;
psrc->last_position = input_index ;
/* Save current ratio rather then target ratio. */
psrc->last_ratio = src_ratio ;
data->input_frames_used = filter->in_used / filter->channels ;
data->output_frames_gen = filter->out_gen / filter->channels ;
return SRC_ERR_NO_ERROR ;
} /* sinc_vari_process */
/*----------------------------------------------------------------------------------------
*/
static void
prepare_data (SINC_FILTER *filter, SRC_DATA *data, int half_filter_chan_len)
{ int len = 0 ;
if (filter->b_real_end >= 0)
return ; /* This doesn't make sense, so return. */
if (filter->b_current == 0)
{ /* Initial state. Set up zeros at the start of the buffer and
** then load new data after that.
*/
len = filter->b_len - 2 * half_filter_chan_len ;
filter->b_current = filter->b_end = half_filter_chan_len ;
}
else if (filter->b_end + half_filter_chan_len + filter->channels < filter->b_len)
{ /* Load data at current end position. */
len = MAX (filter->b_len - filter->b_current - half_filter_chan_len, 0) ;
}
else
{ /* Move data at end of buffer back to the start of the buffer. */
len = filter->b_end - filter->b_current ;
memmove (filter->buffer, filter->buffer + filter->b_current - half_filter_chan_len,
(half_filter_chan_len + len) * sizeof (filter->buffer [0])) ;
filter->b_current = half_filter_chan_len ;
filter->b_end = filter->b_current + len ;
/* Now load data at current end of buffer. */
len = MAX (filter->b_len - filter->b_current - half_filter_chan_len, 0) ;
} ;
len = MIN (filter->in_count - filter->in_used, len) ;
len -= (len % filter->channels) ;
memcpy (filter->buffer + filter->b_end, data->data_in + filter->in_used,
len * sizeof (filter->buffer [0])) ;
filter->b_end += len ;
filter->in_used += len ;
if (filter->in_used == filter->in_count &&
filter->b_end - filter->b_current < 2 * half_filter_chan_len && data->end_of_input)
{ /* Handle the case where all data in the current buffer has been
** consumed and this is the last buffer.
*/
if (filter->b_len - filter->b_end < half_filter_chan_len + 5)
{ /* If necessary, move data down to the start of the buffer. */
len = filter->b_end - filter->b_current ;
memmove (filter->buffer, filter->buffer + filter->b_current - half_filter_chan_len,
(half_filter_chan_len + len) * sizeof (filter->buffer [0])) ;
filter->b_current = half_filter_chan_len ;
filter->b_end = filter->b_current + len ;
} ;
filter->b_real_end = filter->b_end ;
len = half_filter_chan_len + 5 ;
memset (filter->buffer + filter->b_end, 0, len * sizeof (filter->buffer [0])) ;
filter->b_end += len ;
} ;
return ;
} /* prepare_data */
static double
calc_output (SINC_FILTER *filter, increment_t increment, increment_t start_filter_index, int ch)
{ double fraction, left, right, icoeff ;
increment_t filter_index, max_filter_index ;
int data_index, coeff_count, indx ;
/* Convert input parameters into fixed point. */
max_filter_index = INT_TO_FP (filter->coeff_half_len) ;
/* First apply the left half of the filter. */
filter_index = start_filter_index ;
coeff_count = (max_filter_index - filter_index) / increment ;
filter_index = filter_index + coeff_count * increment ;
data_index = filter->b_current - filter->channels * coeff_count + ch ;
left = 0.0 ;
do
{ fraction = FP_TO_DOUBLE (filter_index) ;
indx = FP_TO_INT (filter_index) ;
icoeff = filter->coeffs [indx] + fraction * (filter->coeffs [indx + 1] - filter->coeffs [indx]) ;
left += icoeff * filter->buffer [data_index] ;
filter_index -= increment ;
data_index = data_index + filter->channels ;
}
while (filter_index >= MAKE_INCREMENT_T (0)) ;
/* Now apply the right half of the filter. */
filter_index = increment - start_filter_index ;
coeff_count = (max_filter_index - filter_index) / increment ;
filter_index = filter_index + coeff_count * increment ;
data_index = filter->b_current + filter->channels * (1 + coeff_count) + ch ;
right = 0.0 ;
do
{ fraction = FP_TO_DOUBLE (filter_index) ;
indx = FP_TO_INT (filter_index) ;
icoeff = filter->coeffs [indx] + fraction * (filter->coeffs [indx + 1] - filter->coeffs [indx]) ;
right += icoeff * filter->buffer [data_index] ;
filter_index -= increment ;
data_index = data_index - filter->channels ;
}
while (filter_index > MAKE_INCREMENT_T (0)) ;
return (left + right) ;
} /* calc_output */
/*
** Do not edit or modify anything in this comment block.
** The arch-tag line is a file identity tag for the GNU Arch
** revision control system.
**
** arch-tag: db8efe06-2fbd-487e-be8f-bfc01e68c19f
*/