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Diffstat (limited to 'common/dct.cpp')
| -rw-r--r-- | common/dct.cpp | 208 |
1 files changed, 208 insertions, 0 deletions
diff --git a/common/dct.cpp b/common/dct.cpp new file mode 100644 index 0000000000..6525c727ae --- /dev/null +++ b/common/dct.cpp @@ -0,0 +1,208 @@ +/* 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/cosinetables.h" +#include "common/dct.h" + +namespace Common { + +DCT::DCT(int bits, TransformType trans) : _bits(bits), _trans(trans), _rdft(0) { + int n = 1 << _bits; + + _tCos = getCosineTable(_bits + 2); + + _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; + } +} + +/* 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 = -0.5 * (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) * 0.5; + + 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) * 0.5; + + data[i ] = tmp1 + s; + data[n - i - 1] = tmp1 - s; + } + + _rdft->calc(data); + + float next = data[1] * 0.5; + + 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 = 1.0 / 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) * 0.5; + + data[i ] = s + tmp1; + data[n - i] = s - tmp1; + } + + data[n / 2] *= 2; + + _rdft->calc(data); + + data[0] *= 0.5; + + 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 |