mirror of
https://github.com/libretro/scummvm.git
synced 2024-12-21 09:21:08 +00:00
113 lines
2.8 KiB
C++
113 lines
2.8 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 xoreos' (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>
|
|
|
|
#ifndef COMMON_RDFT_H
|
|
#define COMMON_RDFT_H
|
|
|
|
#include "common/scummsys.h"
|
|
#include "common/math.h"
|
|
#include "common/fft.h"
|
|
|
|
#include "common/cosinetables.h"
|
|
#include "common/sinetables.h"
|
|
|
|
namespace Common {
|
|
|
|
/**
|
|
* (Inverse) Real Discrete Fourier Transform.
|
|
*
|
|
* Used in audio:
|
|
* - QDM2
|
|
*
|
|
* Used in engines:
|
|
* - scumm
|
|
*
|
|
*
|
|
* It has four modes:
|
|
*
|
|
* Below, n = 1 << bits
|
|
*
|
|
* (I)DFT_R2C:
|
|
* input:
|
|
* n real floats
|
|
* output:
|
|
* n/2 complex floats (stored as real part followed by imag part).
|
|
*
|
|
* The output represents the first half of the (I)DFT of the input.
|
|
* If F is the complex (I)DFT of the input, then
|
|
* output[0] = F[0] + i * F[n/2] and
|
|
* output[k] = F[k] for k = 1 .. n/2-1.
|
|
* Note that F[0] and F[k] are real since the input is real, and
|
|
* the remaining values of F can be reconstructed from symmetry if desired.
|
|
*
|
|
* (I)DFT_C2R:
|
|
* input:
|
|
* n/2 complex floats
|
|
* output:
|
|
* n real floats
|
|
*
|
|
* The input encodes a complex vector x of length n that has the
|
|
* required symmetry to have a real (I)DFT:
|
|
* x[0] = Re(input[0])
|
|
* x[k] = input[k] for k = 1 .. n/2-1
|
|
* x[n/2] = Im(input[0])
|
|
* x[k] = conj(input[n-k]) for k = n/2+1 .. n-1
|
|
* The output is then the real (I)DFT of x, divided by 2.
|
|
*
|
|
* TODO: Is this division by 2 intentional?
|
|
*/
|
|
|
|
class RDFT {
|
|
public:
|
|
enum TransformType {
|
|
DFT_R2C,
|
|
IDFT_C2R,
|
|
IDFT_R2C,
|
|
DFT_C2R
|
|
};
|
|
|
|
RDFT(int bits, TransformType trans);
|
|
~RDFT();
|
|
|
|
void calc(float *data);
|
|
|
|
private:
|
|
int _bits;
|
|
int _inverse;
|
|
int _signConvention;
|
|
|
|
SineTable _sin;
|
|
CosineTable _cos;
|
|
const float *_tSin;
|
|
const float *_tCos;
|
|
|
|
FFT *_fft;
|
|
};
|
|
|
|
} // End of namespace Common
|
|
|
|
#endif // COMMON_RDFT_H
|