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/* ResidualVM - A 3D game interpreter
*
* ResidualVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the AUTHORS
* file distributed with this source distribution.
*
* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*/
// Based on xoreos' (I)RDFT code which is in turn
// Based upon the (I)MDCT code in FFmpeg
// Copyright (c) 2002 Fabrice Bellard
/** @file common/mdct.cpp
* (Inverse) Modified Discrete Cosine Transforms.
*/
#include "common/math.h"
#include "common/util.h"
#include "common/fft.h"
#include "common/mdct.h"
namespace Common {
MDCT::MDCT(int bits, bool inverse, double scale) : _bits(bits), _fft(0) {
_size = 1 << bits;
_fft = new FFT(_bits - 2, inverse);
const int size2 = _size >> 1;
const int size4 = _size >> 2;
_tCos = new float[size2];
_tSin = _tCos + size4;
const double theta = 1.0 / 8.0 + (scale < 0 ? size4 : 0);
scale = sqrt(ABS(scale));
for (int i = 0; i < size4; i++) {
const double alpha = 2 * M_PI * (i + theta) / _size;
_tCos[i] = -cos(alpha) * scale;
_tSin[i] = -sin(alpha) * scale;
}
}
MDCT::~MDCT() {
delete[] _tCos;
delete _fft;
}
#define CMUL(dre, dim, are, aim, bre, bim) do { \
(dre) = (are) * (bre) - (aim) * (bim); \
(dim) = (are) * (bim) + (aim) * (bre); \
} while (0)
void MDCT::calcMDCT(float *output, const float *input) {
Complex *x = (Complex *) output;
const int size2 = _size >> 1;
const int size4 = _size >> 2;
const int size8 = _size >> 3;
const int size3 = _size * 3;
const uint16 *revTab = _fft->getRevTab();
// Pre rotation
for (int i = 0; i < size8; i++) {
float re = -input[2 * i + size3] - input[size3 - 1 - 2 * i];
float im = -input[2 * i + size4] + input[size4 - 1 - 2 * i];
int j = revTab[i];
CMUL(x[j].re, x[j].im, re, im, -_tCos[i], _tSin[i]);
re = input[2 * i ] - input[size2 - 1 - 2 * i];
im = -input[2 * i + size2] - input[_size - 1 - 2 * i];
j = revTab[size8 + i];
CMUL(x[j].re, x[j].im, re, im, -_tCos[size8 + i], _tSin[size8 + i]);
}
_fft->calc(x);
// Post rotation
for (int i = 0; i < size8; i++) {
float r0, i0, r1, i1;
CMUL(i1, r0, x[size8-i-1].re, x[size8-i-1].im, -_tSin[size8-i-1], -_tCos[size8-i-1]);
CMUL(i0, r1, x[size8+i ].re, x[size8+i ].im, -_tSin[size8+i ], -_tCos[size8+i ]);
x[size8 - i - 1].re = r0;
x[size8 - i - 1].im = i0;
x[size8 + i ].re = r1;
x[size8 + i ].im = i1;
}
}
void MDCT::calcIMDCT(float *output, const float *input) {
const int size2 = _size >> 1;
const int size4 = _size >> 2;
calcHalfIMDCT(output + size4, input);
for (int k = 0; k < size4; k++) {
output[ k ] = -output[size2 - k - 1];
output[_size - k - 1] = output[size2 + k ];
}
}
void MDCT::calcHalfIMDCT(float *output, const float *input) {
Complex *z = (Complex *) output;
const int size2 = _size >> 1;
const int size4 = _size >> 2;
const int size8 = _size >> 3;
const uint16 *revTab = _fft->getRevTab();
// Pre rotation
const float *in1 = input;
const float *in2 = input + size2 - 1;
for (int k = 0; k < size4; k++) {
const int j = revTab[k];
CMUL(z[j].re, z[j].im, *in2, *in1, _tCos[k], _tSin[k]);
in1 += 2;
in2 -= 2;
}
_fft->calc(z);
// Post rotation + reordering
for (int k = 0; k < size8; k++) {
float r0, i0, r1, i1;
CMUL(r0, i1, z[size8-k-1].im, z[size8-k-1].re, _tSin[size8-k-1], _tCos[size8-k-1]);
CMUL(r1, i0, z[size8+k ].im, z[size8+k ].re, _tSin[size8+k ], _tCos[size8+k ]);
z[size8 - k - 1].re = r0;
z[size8 - k - 1].im = i0;
z[size8 + k ].re = r1;
z[size8 + k ].im = i1;
}
}
} // End of namespace Common
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