mirror of
https://github.com/libretro/scummvm.git
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ec24687ce4
Adding @defgroup and @ingroup doxygen tags into all headers in the common folder that contain doxygen blocks. This improves the structure, readability, and findability of information in the resulting output. This commit targets purely structure and does not deal with the content of the currently existing doxygen documentation.
124 lines
3.0 KiB
C++
124 lines
3.0 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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*/
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// Based on xoreos' (I)RDFT code which is in turn
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// Based upon the (I)RDFT code in FFmpeg
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// Copyright (c) 2009 Alex Converse <alex dot converse at gmail dot com>
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#ifndef COMMON_RDFT_H
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#define COMMON_RDFT_H
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#include "common/scummsys.h"
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#include "common/math.h"
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#include "common/fft.h"
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#include "common/cosinetables.h"
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#include "common/sinetables.h"
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namespace Common {
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/**
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* @defgroup common_rdft RDFT algorithm
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* @ingroup common
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*
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* @brief API for the Real Discrete Fourier Transform (RDFT) algorithm.
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*
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* @{
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*/
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/**
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* @brief (Inverse) Real Discrete Fourier Transform.
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*
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* @details Used in audio:
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* - QDM2
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*
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* Used in engines:
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* - scumm
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*
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*
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* It has four modes:
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*
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* Below, n = 1 << bits
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*
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* (I)DFT_R2C:
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* input:
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* n real floats
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* output:
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* n/2 complex floats (stored as real part followed by imag part).
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*
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* The output represents the first half of the (I)DFT of the input.
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* If F is the complex (I)DFT of the input, then
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* output[0] = F[0] + i * F[n/2] and
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* output[k] = F[k] for k = 1 .. n/2-1.
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* Note that F[0] and F[k] are real since the input is real, and
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* the remaining values of F can be reconstructed from symmetry if desired.
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*
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* (I)DFT_C2R:
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* input:
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* n/2 complex floats
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* output:
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* n real floats
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*
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* The input encodes a complex vector x of length n that has the
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* required symmetry to have a real (I)DFT:
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* x[0] = Re(input[0])
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* x[k] = input[k] for k = 1 .. n/2-1
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* x[n/2] = Im(input[0])
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* x[k] = conj(input[n-k]) for k = n/2+1 .. n-1
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* The output is then the real (I)DFT of x, divided by 2.
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*
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* TODO: Is this division by 2 intentional?
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*/
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class RDFT {
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public:
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enum TransformType {
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DFT_R2C,
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IDFT_C2R,
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IDFT_R2C,
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DFT_C2R
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};
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RDFT(int bits, TransformType trans);
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~RDFT();
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void calc(float *data);
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private:
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int _bits;
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int _inverse;
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int _signConvention;
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SineTable _sin;
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CosineTable _cos;
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const float *_tSin;
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const float *_tCos;
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FFT *_fft;
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};
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/** @} */
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} // End of namespace Common
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#endif // COMMON_RDFT_H
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