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diff --git a/common/fft.h b/common/fft.h
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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)FFT code which is in turn
+// based upon the (I)FFT code in FFmpeg
+// Copyright (c) 2008 Loren Merritt
+// Copyright (c) 2002 Fabrice Bellard
+// Partly based on libdjbfft by D. J. Bernstein
+
+#ifndef COMMON_FFT_H
+#define COMMON_FFT_H
+
+#include "common/scummsys.h"
+#include "common/math.h"
+
+namespace Common {
+
+/**
+ * (Inverse) Fast Fourier Transform.
+ *
+ * Used in engines:
+ *  - scumm
+ */
+class FFT {
+public:
+	FFT(int bits, int inverse);
+	~FFT();
+
+	/** Do the permutation needed BEFORE calling calc(). */
+	void permute(Complex *z);
+
+	/** Do a complex FFT.
+	 *
+	 *  The input data must be permuted before.
+	 *  No 1.0/sqrt(n) normalization is done.
+	 */
+	void calc(Complex *z);
+
+private:
+	int _bits;
+	int _inverse;
+
+	uint16 *_revTab;
+
+	Complex *_expTab;
+	Complex *_tmpBuf;
+
+	const float *_tSin;
+	const float *_tCos;
+
+	int _splitRadix;
+	int _permutation;
+
+	static int splitRadixPermutation(int i, int n, int inverse);
+};
+
+} // End of namespace Common
+
+#endif // COMMON_FFT_H