mirror of
https://github.com/libretro/scummvm.git
synced 2024-12-03 15:41:41 +00:00
101 lines
2.9 KiB
C++
101 lines
2.9 KiB
C++
/* ScummVM - Graphic Adventure Engine
|
|
*
|
|
* ScummVM is the legal property of its developers, whose names
|
|
* are too numerous to list here. Please refer to the COPYRIGHT
|
|
* 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 eos' (I)RDFT code which is in turn
|
|
// Based upon the (I)RDFT code in FFmpeg
|
|
// Copyright (c) 2009 Alex Converse <alex dot converse at gmail dot com>
|
|
|
|
#include "common/rdft.h"
|
|
|
|
namespace Common {
|
|
|
|
RDFT::RDFT(int bits, TransformType trans) : _bits(bits), _sin(bits), _cos(bits), _fft(nullptr) {
|
|
assert((_bits >= 4) && (_bits <= 16));
|
|
|
|
_inverse = trans == IDFT_C2R || trans == DFT_C2R;
|
|
_signConvention = trans == IDFT_R2C || trans == DFT_C2R ? 1 : -1;
|
|
|
|
_fft = new FFT(bits - 1, trans == IDFT_C2R || trans == IDFT_R2C);
|
|
|
|
int n = 1 << bits;
|
|
|
|
_tSin = _sin.getTable() + (trans == DFT_R2C || trans == DFT_C2R) * (n >> 2);
|
|
_tCos = _cos.getTable();
|
|
}
|
|
|
|
RDFT::~RDFT() {
|
|
delete _fft;
|
|
}
|
|
|
|
void RDFT::calc(float *data) {
|
|
const int n = 1 << _bits;
|
|
|
|
const float k1 = 0.5f;
|
|
const float k2 = 0.5f - _inverse;
|
|
|
|
if (!_inverse) {
|
|
_fft->permute((Complex *)data);
|
|
_fft->calc ((Complex *)data);
|
|
}
|
|
|
|
Complex ev, od;
|
|
|
|
/* i=0 is a special case because of packing, the DC term is real, so we
|
|
are going to throw the N/2 term (also real) in with it. */
|
|
|
|
ev.re = data[0];
|
|
|
|
data[0] = ev.re + data[1];
|
|
data[1] = ev.re - data[1];
|
|
|
|
int i;
|
|
for (i = 1; i < (n >> 2); i++) {
|
|
int i1 = 2 * i;
|
|
int i2 = n - i1;
|
|
|
|
/* Separate even and odd FFTs */
|
|
ev.re = k1 * (data[i1 ] + data[i2 ]);
|
|
od.im = -k2 * (data[i1 ] - data[i2 ]);
|
|
ev.im = k1 * (data[i1 + 1] - data[i2 + 1]);
|
|
od.re = k2 * (data[i1 + 1] + data[i2 + 1]);
|
|
|
|
/* Apply twiddle factors to the odd FFT and add to the even FFT */
|
|
data[i1 ] = ev.re + od.re * _tCos[i] - od.im * _tSin[i];
|
|
data[i1 + 1] = ev.im + od.im * _tCos[i] + od.re * _tSin[i];
|
|
data[i2 ] = ev.re - od.re * _tCos[i] + od.im * _tSin[i];
|
|
data[i2 + 1] = -ev.im + od.im * _tCos[i] + od.re * _tSin[i];
|
|
}
|
|
|
|
data[2 * i + 1] = _signConvention * data[2 * i + 1];
|
|
|
|
if (_inverse) {
|
|
data[0] *= k1;
|
|
data[1] *= k1;
|
|
|
|
_fft->permute((Complex *)data);
|
|
_fft->calc ((Complex *)data);
|
|
}
|
|
|
|
}
|
|
|
|
} // End of namespace Common
|