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/* 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)DCT code in FFmpeg
// Copyright (c) 2009 Peter Ross <pross@xvid.org>
// Copyright (c) 2010 Alex Converse <alex.converse@gmail.com>
// Copyright (c) 2010 Vitor Sessak
#include "common/dct.h"
namespace Common {
DCT::DCT(int bits, TransformType trans) : _bits(bits), _cos(1 << (_bits + 2) ), _trans(trans), _rdft(nullptr) {
int n = 1 << _bits;
_tCos = _cos.getTable();
_csc2 = new float[n / 2];
_rdft = new RDFT(_bits, (_trans == DCT_III) ? RDFT::IDFT_C2R : RDFT::DFT_R2C);
for (int i = 0; i < (n / 2); i++)
_csc2[i] = 0.5 / sin((M_PI / (2 * n) * (2 * i + 1)));
}
DCT::~DCT() {
delete _rdft;
delete[] _csc2;
}
void DCT::calc(float *data) {
switch (_trans) {
case DCT_I:
calcDCTI(data);
break;
case DCT_II:
calcDCTII(data);
break;
case DCT_III:
calcDCTIII(data);
break;
case DST_I:
calcDSTI(data);
break;
default:
break;
}
}
/* sin((M_PI * x / (2*n)) */
#define SIN(n,x) (_tCos[(n) - (x)])
/* cos((M_PI * x / (2*n)) */
#define COS(n,x) (_tCos[x])
void DCT::calcDCTI(float *data) {
int n = 1 << _bits;
float next = -0.5f * (data[0] - data[n]);
for (int i = 0; i < (n / 2); i++) {
float tmp1 = data[i ];
float tmp2 = data[n - i];
float s = SIN(n, 2 * i);
float c = COS(n, 2 * i);
c *= tmp1 - tmp2;
s *= tmp1 - tmp2;
next += c;
tmp1 = (tmp1 + tmp2) * 0.5f;
data[i ] = tmp1 - s;
data[n - i] = tmp1 + s;
}
_rdft->calc(data);
data[n] = data[1];
data[1] = next;
for (int i = 3; i <= n; i += 2)
data[i] = data[i - 2] - data[i];
}
void DCT::calcDCTII(float *data) {
int n = 1 << _bits;
for (int i = 0; i < (n / 2); i++) {
float tmp1 = data[i ];
float tmp2 = data[n - i - 1];
float s = SIN(n, 2 * i + 1);
s *= tmp1 - tmp2;
tmp1 = (tmp1 + tmp2) * 0.5f;
data[i ] = tmp1 + s;
data[n - i - 1] = tmp1 - s;
}
_rdft->calc(data);
float next = data[1] * 0.5f;
data[1] *= -1;
for (int i = n - 2; i >= 0; i -= 2) {
float inr = data[i ];
float ini = data[i + 1];
float c = COS(n, i);
float s = SIN(n, i);
data[i ] = c * inr + s * ini;
data[i + 1] = next;
next += s * inr - c * ini;
}
}
void DCT::calcDCTIII(float *data) {
int n = 1 << _bits;
float next = data[n - 1];
float inv_n = 1.0f / n;
for (int i = n - 2; i >= 2; i -= 2) {
float val1 = data[i ];
float val2 = data[i - 1] - data[i + 1];
float c = COS(n, i);
float s = SIN(n, i);
data[i ] = c * val1 + s * val2;
data[i + 1] = s * val1 - c * val2;
}
data[1] = 2 * next;
_rdft->calc(data);
for (int i = 0; i < (n / 2); i++) {
float tmp1 = data[i ] * inv_n;
float tmp2 = data[n - i - 1] * inv_n;
float csc = _csc2[i] * (tmp1 - tmp2);
tmp1 += tmp2;
data[i ] = tmp1 + csc;
data[n - i - 1] = tmp1 - csc;
}
}
void DCT::calcDSTI(float *data) {
int n = 1 << _bits;
data[0] = 0;
for (int i = 1; i < (n / 2); i++) {
float tmp1 = data[i ];
float tmp2 = data[n - i];
float s = SIN(n, 2 * i);
s *= tmp1 + tmp2;
tmp1 = (tmp1 - tmp2) * 0.5f;
data[i ] = s + tmp1;
data[n - i] = s - tmp1;
}
data[n / 2] *= 2;
_rdft->calc(data);
data[0] *= 0.5f;
for (int i = 1; i < (n - 2); i += 2) {
data[i + 1] += data[i - 1];
data[i ] = -data[i + 2];
}
data[n - 1] = 0;
}
} // End of namespace Common
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