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// -------------------------------------------------------------------------
//
// Copyright (C) 2010-2014 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 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., 675 Mass Ave, Cambridge, MA 02139, USA.
//
// -------------------------------------------------------------------------
#include <string.h>
#include <math.h>
#include "dither.h"
float Dither::_div = 0;
#define SCALE 32768.0f
#define LIMIT 32767
Dither::Dither (void)
{
reset ();
_div = ldexpf (1.0f, 32);
}
void Dither::reset (void)
{
memset (_err, 0, (SIZE + 4) * sizeof(float));
_ind = SIZE - 1;
_ran = 1234567;
}
void Dither::proc_rectangular (int nsam, const float *srce, int16_t *dest, int ds, int dd)
{
float v, r;
int16_t k;
while (nsam--)
{
r = genrand () - 0.5f;
v = *srce * SCALE + r;
k = lrintf (v);
if (k < -LIMIT) k = -LIMIT;
else if (k > LIMIT) k = LIMIT;
*dest = k;
srce += ds;
dest += dd;
}
}
void Dither::proc_triangular (int nsam, const float *srce, int16_t *dest, int ds, int dd)
{
float v, r0, r1;
int16_t k;
r1 = *_err;
while (nsam--)
{
r0 = genrand ();
v = *srce * SCALE + r0 - r1;
r1 = r0;
k = lrintf (v);
if (k < -LIMIT) k = -LIMIT;
else if (k > LIMIT) k = LIMIT;
*dest = k;
srce += ds;
dest += dd;
}
*_err = r1;
}
void Dither::proc_lipschitz (int nsam, const float *srce, int16_t *dest, int ds, int dd)
{
float e, u, v, *p;
int i;
int16_t k;
i = _ind;
while (nsam--)
{
p = _err + i;
u = *srce * SCALE
- 2.033f * p [0]
+ 2.165f * p [1]
- 1.959f * p [2]
+ 1.590f * p [3]
- 0.615f * p [4];
v = u + genrand () - genrand ();
k = lrintf (v);
e = k - u;
if (k < -LIMIT) k = -LIMIT;
else if (k > LIMIT) k = LIMIT;
*dest = k;
if (--i < 0)
{
_err [SIZE + 0] = _err [0];
_err [SIZE + 1] = _err [1];
_err [SIZE + 2] = _err [2];
_err [SIZE + 3] = _err [3];
i += SIZE;
}
_err [i] = e;
srce += ds;
dest += dd;
}
_ind = i;
}
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