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// ----------------------------------------------------------------------------
//
// Copyright (C) 2006-2012 Fons Adriaensen <fons@linuxaudio.org>
//
// 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 3 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, see <http://www.gnu.org/licenses/>.
//
// ----------------------------------------------------------------------------
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include "zita-resampler/resampler-table.h"
using namespace ArdourZita;
Resampler_table *Resampler_table::_list = 0;
Resampler_mutex Resampler_table::_mutex;
static double sinc (double x)
{
x = fabs (x);
if (x < 1e-6) return 1.0;
x *= M_PI;
return sin (x) / x;
}
static double wind (double x)
{
x = fabs (x);
if (x >= 1.0) return 0.0f;
x *= M_PI;
return 0.384 + 0.500 * cos (x) + 0.116 * cos (2 * x);
}
Resampler_table::Resampler_table (double fr, unsigned int hl, unsigned int np)
: _next (0)
, _refc (0)
, _fr (fr)
, _hl (hl)
, _np (np)
{
unsigned int i, j;
double t;
float *p;
_ctab = new float [hl * (np + 1)];
p = _ctab;
for (j = 0; j <= np; j++) {
t = (double) j / (double) np;
for (i = 0; i < hl; i++) {
p [hl - i - 1] = (float)(fr * sinc (t * fr) * wind (t / hl));
t += 1;
}
p += hl;
}
}
Resampler_table::~Resampler_table (void)
{
delete[] _ctab;
}
Resampler_table*
Resampler_table::create (double fr, unsigned int hl, unsigned int np)
{
Resampler_table *P;
_mutex.lock ();
P = _list;
while (P) {
if ((fr >= P->_fr * 0.999) && (fr <= P->_fr * 1.001) && (hl == P->_hl) && (np == P->_np)) {
P->_refc++;
_mutex.unlock ();
return P;
}
P = P->_next;
}
P = new Resampler_table (fr, hl, np);
P->_refc = 1;
P->_next = _list;
_list = P;
_mutex.unlock ();
return P;
}
void
Resampler_table::destroy (Resampler_table *T)
{
Resampler_table *P, *Q;
_mutex.lock ();
if (T) {
T->_refc--;
if (T->_refc == 0) {
P = _list;
Q = 0;
while (P) {
if (P == T) {
if (Q) Q->_next = T->_next;
else _list = T->_next;
break;
}
Q = P;
P = P->_next;
}
delete T;
}
}
_mutex.unlock ();
}
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