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+
+/* -----------------------------------------------------------------------------------------------------------
+Software License for The Fraunhofer FDK AAC Codec Library for Android
+
+© Copyright  1995 - 2012 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
+  All rights reserved.
+
+ 1.    INTRODUCTION
+The Fraunhofer FDK AAC Codec Library for Android ("FDK AAC Codec") is software that implements
+the MPEG Advanced Audio Coding ("AAC") encoding and decoding scheme for digital audio.
+This FDK AAC Codec software is intended to be used on a wide variety of Android devices.
+
+AAC's HE-AAC and HE-AAC v2 versions are regarded as today's most efficient general perceptual
+audio codecs. AAC-ELD is considered the best-performing full-bandwidth communications codec by
+independent studies and is widely deployed. AAC has been standardized by ISO and IEC as part
+of the MPEG specifications.
+
+Patent licenses for necessary patent claims for the FDK AAC Codec (including those of Fraunhofer)
+may be obtained through Via Licensing (www.vialicensing.com) or through the respective patent owners
+individually for the purpose of encoding or decoding bit streams in products that are compliant with
+the ISO/IEC MPEG audio standards. Please note that most manufacturers of Android devices already license
+these patent claims through Via Licensing or directly from the patent owners, and therefore FDK AAC Codec
+software may already be covered under those patent licenses when it is used for those licensed purposes only.
+
+Commercially-licensed AAC software libraries, including floating-point versions with enhanced sound quality,
+are also available from Fraunhofer. Users are encouraged to check the Fraunhofer website for additional
+applications information and documentation.
+
+2.    COPYRIGHT LICENSE
+
+Redistribution and use in source and binary forms, with or without modification, are permitted without
+payment of copyright license fees provided that you satisfy the following conditions:
+
+You must retain the complete text of this software license in redistributions of the FDK AAC Codec or
+your modifications thereto in source code form.
+
+You must retain the complete text of this software license in the documentation and/or other materials
+provided with redistributions of the FDK AAC Codec or your modifications thereto in binary form.
+You must make available free of charge copies of the complete source code of the FDK AAC Codec and your
+modifications thereto to recipients of copies in binary form.
+
+The name of Fraunhofer may not be used to endorse or promote products derived from this library without
+prior written permission.
+
+You may not charge copyright license fees for anyone to use, copy or distribute the FDK AAC Codec
+software or your modifications thereto.
+
+Your modified versions of the FDK AAC Codec must carry prominent notices stating that you changed the software
+and the date of any change. For modified versions of the FDK AAC Codec, the term
+"Fraunhofer FDK AAC Codec Library for Android" must be replaced by the term
+"Third-Party Modified Version of the Fraunhofer FDK AAC Codec Library for Android."
+
+3.    NO PATENT LICENSE
+
+NO EXPRESS OR IMPLIED LICENSES TO ANY PATENT CLAIMS, including without limitation the patents of Fraunhofer,
+ARE GRANTED BY THIS SOFTWARE LICENSE. Fraunhofer provides no warranty of patent non-infringement with
+respect to this software.
+
+You may use this FDK AAC Codec software or modifications thereto only for purposes that are authorized
+by appropriate patent licenses.
+
+4.    DISCLAIMER
+
+This FDK AAC Codec software is provided by Fraunhofer on behalf of the copyright holders and contributors
+"AS IS" and WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, including but not limited to the implied warranties
+of merchantability and fitness for a particular purpose. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+CONTRIBUTORS BE LIABLE for any direct, indirect, incidental, special, exemplary, or consequential damages,
+including but not limited to procurement of substitute goods or services; loss of use, data, or profits,
+or business interruption, however caused and on any theory of liability, whether in contract, strict
+liability, or tort (including negligence), arising in any way out of the use of this software, even if
+advised of the possibility of such damage.
+
+5.    CONTACT INFORMATION
+
+Fraunhofer Institute for Integrated Circuits IIS
+Attention: Audio and Multimedia Departments - FDK AAC LL
+Am Wolfsmantel 33
+91058 Erlangen, Germany
+
+www.iis.fraunhofer.de/amm
+amm-info@iis.fraunhofer.de
+----------------------------------------------------------------------------------------------------------- */
+
+/***************************  Fraunhofer IIS FDK Tools  **********************
+
+   Author(s):   Josef Hoepfl, DSP Solutions
+   Description: Fix point FFT
+
+******************************************************************************/
+
+#ifndef __FFT_H__
+#define __FFT_H__
+
+#include "common_fix.h"
+
+/**
+ * \brief Perform an inplace complex valued FFT of length 2^n
+ *
+ * \param length Length of the FFT to be calculated.
+ * \param pInput Input/Output data buffer. The input data must have at least 1 bit scale headroom.
+ *          The values are interleaved, real/imag pairs.
+ * \param scalefactor Pointer to an INT, which contains the current scale of the input data,
+ *                    which is updated according to the FFT scale.
+ */
+void fft(int length, FIXP_DBL *pInput, INT *scalefactor);
+
+/**
+ * \brief Perform an inplace complex valued IFFT of length 2^n
+ *
+ * \param length Length of the FFT to be calculated.
+ * \param pInput Input/Output data buffer. The input data must have at least 1 bit scale headroom.
+ *          The values are interleaved, real/imag pairs.
+ * \param scalefactor Pointer to an INT, which contains the current scale of the input data,
+ *                    which is updated according to the IFFT scale.
+ */
+void ifft(int length, FIXP_DBL *pInput, INT *scalefactor);
+
+
+/*
+ * Frequently used and fixed short length FFTs.
+ */
+
+LNK_SECTION_CODE_L1
+static void FORCEINLINE fft_4(FIXP_DBL *x)
+{
+    FIXP_DBL a00, a10, a20, a30, tmp0, tmp1;
+
+    a00 = (x[0] + x[4])>>1;  /* Re A + Re B */
+    a10 = (x[2] + x[6])>>1;  /* Re C + Re D */
+    a20 = (x[1] + x[5])>>1;  /* Im A + Im B */
+    a30 = (x[3] + x[7])>>1;  /* Im C + Im D */
+
+    x[0] = a00 + a10;       /* Re A' = Re A + Re B + Re C + Re D */
+    x[1] = a20 + a30;       /* Im A' = Im A + Im B + Im C + Im D */
+
+    tmp0 = a00 - x[4];       /* Re A - Re B */
+    tmp1 = a20 - x[5];       /* Im A - Im B */
+
+    x[4] = a00 - a10;       /* Re C' = Re A + Re B - Re C - Re D */
+    x[5] = a20 - a30;       /* Im C' = Im A + Im B - Im C - Im D */
+
+    a10 = a10 - x[6];       /* Re C - Re D */
+    a30 = a30 - x[7];       /* Im C - Im D */
+
+    x[2] = tmp0 + a30;       /* Re B' = Re A - Re B + Im C - Im D */
+    x[6] = tmp0 - a30;       /* Re D' = Re A - Re B - Im C + Im D */
+    x[3] = tmp1 - a10;       /* Im B' = Im A - Im B - Re C + Re D */
+    x[7] = tmp1 + a10;       /* Im D' = Im A - Im B + Re C - Re D */
+}
+
+LNK_SECTION_CODE_L1
+static void FORCEINLINE fft_8(FIXP_DBL *x)
+{
+      #define W_PiFOURTH STC(0x5a82799a)
+
+      FIXP_DBL a00, a10, a20, a30;
+      FIXP_DBL y[16];
+
+      a00 = (x[0] + x[8])>>1;
+      a10 =  x[4] + x[12];
+      a20 = (x[1] + x[9])>>1;
+      a30 =  x[5] + x[13];
+
+      y[0] = a00 + (a10>>1);
+      y[4] = a00 - (a10>>1);
+      y[1] = a20 + (a30>>1);
+      y[5] = a20 - (a30>>1);
+
+      a00 = a00      - x[8];
+      a10 = (a10>>1) - x[12];
+      a20 = a20      - x[9];
+      a30 = (a30>>1) - x[13];
+
+      y[2] = a00 + a30;
+      y[6] = a00 - a30;
+      y[3] = a20 - a10;
+      y[7] = a20 + a10;
+
+      a00 = (x[2] + x[10])>>1;
+      a10 =  x[6] + x[14];
+      a20 = (x[3] + x[11])>>1;
+      a30 =  x[7] + x[15];
+
+      y[8]  = a00 + (a10>>1);
+      y[12] = a00 - (a10>>1);
+      y[9]  = a20 + (a30>>1);
+      y[13] = a20 - (a30>>1);
+
+      a00 = a00      - x[10];
+      a10 = (a10>>1) - x[14];
+      a20 = a20      - x[11];
+      a30 = (a30>>1) - x[15];
+
+      y[10] = a00 + a30;
+      y[14] = a00 - a30;
+      y[11] = a20 - a10;
+      y[15] = a20 + a10;
+
+      FIXP_DBL vr, vi, ur, ui;
+
+      ur = y[0]>>1;
+      ui = y[1]>>1;
+      vr = y[8];
+      vi = y[9];
+      x[0] = ur + (vr>>1);
+      x[1] = ui + (vi>>1);
+      x[8] = ur - (vr>>1);
+      x[9] = ui - (vi>>1);
+
+      ur = y[4]>>1;
+      ui = y[5]>>1;
+      vi = y[12];
+      vr = y[13];
+      x[4]  = ur + (vr>>1);
+      x[5]  = ui - (vi>>1);
+      x[12] = ur - (vr>>1);
+      x[13] = ui + (vi>>1);
+
+      ur = y[10];
+      ui = y[11];
+      vr = fMultDiv2(ui+ur,W_PiFOURTH);
+      vi = fMultDiv2(ui-ur,W_PiFOURTH);
+      ur = y[2];
+      ui = y[3];
+      x[2]  = (ur>>1) + vr;
+      x[3]  = (ui>>1) + vi;
+      x[10] = (ur>>1) - vr;
+      x[11] = (ui>>1) - vi;
+
+      ur = y[14];
+      ui = y[15];
+      vr = fMultDiv2(ui-ur,W_PiFOURTH);
+      vi = fMultDiv2(ui+ur,W_PiFOURTH);
+      ur = y[6];
+      ui = y[7];
+      x[6]  = (ur>>1) + vr;
+      x[7]  = (ui>>1) - vi;
+      x[14] = (ur>>1) - vr;
+      x[15] = (ui>>1) + vi;
+}
+
+/**
+ * \brief FFT of fixed length 16
+ */
+inline void fft_16(FIXP_DBL *x);
+
+/**
+ * \brief FFT of fixed length 32
+ */
+inline void fft_32(FIXP_DBL *x);
+
+
+#endif