libFDK/include/fft.h

   1
   2 /* -----------------------------------------------------------------------------------------------------------
   3 Software License for The Fraunhofer FDK AAC Codec Library for Android
   4
   5 © Copyright  1995 - 2013 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
   6   All rights reserved.
   7
   8  1.    INTRODUCTION
   9 The Fraunhofer FDK AAC Codec Library for Android ("FDK AAC Codec") is software that implements
  10 the MPEG Advanced Audio Coding ("AAC") encoding and decoding scheme for digital audio.
  11 This FDK AAC Codec software is intended to be used on a wide variety of Android devices.
  12
  13 AAC's HE-AAC and HE-AAC v2 versions are regarded as today's most efficient general perceptual
  14 audio codecs. AAC-ELD is considered the best-performing full-bandwidth communications codec by
  15 independent studies and is widely deployed. AAC has been standardized by ISO and IEC as part
  16 of the MPEG specifications.
  17
  18 Patent licenses for necessary patent claims for the FDK AAC Codec (including those of Fraunhofer)
  19 may be obtained through Via Licensing (www.vialicensing.com) or through the respective patent owners
  20 individually for the purpose of encoding or decoding bit streams in products that are compliant with
  21 the ISO/IEC MPEG audio standards. Please note that most manufacturers of Android devices already license
  22 these patent claims through Via Licensing or directly from the patent owners, and therefore FDK AAC Codec
  23 software may already be covered under those patent licenses when it is used for those licensed purposes only.
  24
  25 Commercially-licensed AAC software libraries, including floating-point versions with enhanced sound quality,
  26 are also available from Fraunhofer. Users are encouraged to check the Fraunhofer website for additional
  27 applications information and documentation.
  28
  29 2.    COPYRIGHT LICENSE
  30
  31 Redistribution and use in source and binary forms, with or without modification, are permitted without
  32 payment of copyright license fees provided that you satisfy the following conditions:
  33
  34 You must retain the complete text of this software license in redistributions of the FDK AAC Codec or
  35 your modifications thereto in source code form.
  36
  37 You must retain the complete text of this software license in the documentation and/or other materials
  38 provided with redistributions of the FDK AAC Codec or your modifications thereto in binary form.
  39 You must make available free of charge copies of the complete source code of the FDK AAC Codec and your
  40 modifications thereto to recipients of copies in binary form.
  41
  42 The name of Fraunhofer may not be used to endorse or promote products derived from this library without
  43 prior written permission.
  44
  45 You may not charge copyright license fees for anyone to use, copy or distribute the FDK AAC Codec
  46 software or your modifications thereto.
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  48 Your modified versions of the FDK AAC Codec must carry prominent notices stating that you changed the software
  49 and the date of any change. For modified versions of the FDK AAC Codec, the term
  50 "Fraunhofer FDK AAC Codec Library for Android" must be replaced by the term
  51 "Third-Party Modified Version of the Fraunhofer FDK AAC Codec Library for Android."
  52
  53 3.    NO PATENT LICENSE
  54
  55 NO EXPRESS OR IMPLIED LICENSES TO ANY PATENT CLAIMS, including without limitation the patents of Fraunhofer,
  56 ARE GRANTED BY THIS SOFTWARE LICENSE. Fraunhofer provides no warranty of patent non-infringement with
  57 respect to this software.
  58
  59 You may use this FDK AAC Codec software or modifications thereto only for purposes that are authorized
  60 by appropriate patent licenses.
  61
  62 4.    DISCLAIMER
  63
  64 This FDK AAC Codec software is provided by Fraunhofer on behalf of the copyright holders and contributors
  65 "AS IS" and WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, including but not limited to the implied warranties
  66 of merchantability and fitness for a particular purpose. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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  70 liability, or tort (including negligence), arising in any way out of the use of this software, even if
  71 advised of the possibility of such damage.
  72
  73 5.    CONTACT INFORMATION
  74
  75 Fraunhofer Institute for Integrated Circuits IIS
  76 Attention: Audio and Multimedia Departments - FDK AAC LL
  77 Am Wolfsmantel 33
  78 91058 Erlangen, Germany
  79
  80 www.iis.fraunhofer.de/amm
  81 amm-info@iis.fraunhofer.de
  82 ----------------------------------------------------------------------------------------------------------- */
  83
  84 /***************************  Fraunhofer IIS FDK Tools  **********************
  85
  86    Author(s):   Josef Hoepfl, DSP Solutions
  87    Description: Fix point FFT
  88
  89 ******************************************************************************/
  90
  91 #ifndef __FFT_H__
  92 #define __FFT_H__
  93
  94 #include "common_fix.h"
  95
  96 /**
  97  * \brief Perform an inplace complex valued FFT of length 2^n
  98  *
  99  * \param length Length of the FFT to be calculated.
 100  * \param pInput Input/Output data buffer. The input data must have at least 1 bit scale headroom.
 101  *          The values are interleaved, real/imag pairs.
 102  * \param scalefactor Pointer to an INT, which contains the current scale of the input data,
 103  *                    which is updated according to the FFT scale.
 104  */
 105 void fft(int length, FIXP_DBL *pInput, INT *scalefactor);
 106
 107 /**
 108  * \brief Perform an inplace complex valued IFFT of length 2^n
 109  *
 110  * \param length Length of the FFT to be calculated.
 111  * \param pInput Input/Output data buffer. The input data must have at least 1 bit scale headroom.
 112  *          The values are interleaved, real/imag pairs.
 113  * \param scalefactor Pointer to an INT, which contains the current scale of the input data,
 114  *                    which is updated according to the IFFT scale.
 115  */
 116 void ifft(int length, FIXP_DBL *pInput, INT *scalefactor);
 117
 118
 119 /*
 120  * Frequently used and fixed short length FFTs.
 121  */
 122
 123 LNK_SECTION_CODE_L1
 124 static void FORCEINLINE fft_4(FIXP_DBL *x)
 125 {
 126     FIXP_DBL a00, a10, a20, a30, tmp0, tmp1;
 127
 128     a00 = (x[0] + x[4])>>1;  /* Re A + Re B */
 129     a10 = (x[2] + x[6])>>1;  /* Re C + Re D */
 130     a20 = (x[1] + x[5])>>1;  /* Im A + Im B */
 131     a30 = (x[3] + x[7])>>1;  /* Im C + Im D */
 132
 133     x[0] = a00 + a10;       /* Re A' = Re A + Re B + Re C + Re D */
 134     x[1] = a20 + a30;       /* Im A' = Im A + Im B + Im C + Im D */
 135
 136     tmp0 = a00 - x[4];       /* Re A - Re B */
 137     tmp1 = a20 - x[5];       /* Im A - Im B */
 138
 139     x[4] = a00 - a10;       /* Re C' = Re A + Re B - Re C - Re D */
 140     x[5] = a20 - a30;       /* Im C' = Im A + Im B - Im C - Im D */
 141
 142     a10 = a10 - x[6];       /* Re C - Re D */
 143     a30 = a30 - x[7];       /* Im C - Im D */
 144
 145     x[2] = tmp0 + a30;       /* Re B' = Re A - Re B + Im C - Im D */
 146     x[6] = tmp0 - a30;       /* Re D' = Re A - Re B - Im C + Im D */
 147     x[3] = tmp1 - a10;       /* Im B' = Im A - Im B - Re C + Re D */
 148     x[7] = tmp1 + a10;       /* Im D' = Im A - Im B + Re C - Re D */
 149 }
 150
 151 LNK_SECTION_CODE_L1
 152 static void FORCEINLINE fft_8(FIXP_DBL *x)
 153 {
 154       #define W_PiFOURTH STC(0x5a82799a)
 155
 156       FIXP_DBL a00, a10, a20, a30;
 157       FIXP_DBL y[16];
 158
 159       a00 = (x[0] + x[8])>>1;
 160       a10 =  x[4] + x[12];
 161       a20 = (x[1] + x[9])>>1;
 162       a30 =  x[5] + x[13];
 163
 164       y[0] = a00 + (a10>>1);
 165       y[4] = a00 - (a10>>1);
 166       y[1] = a20 + (a30>>1);
 167       y[5] = a20 - (a30>>1);
 168
 169       a00 = a00      - x[8];
 170       a10 = (a10>>1) - x[12];
 171       a20 = a20      - x[9];
 172       a30 = (a30>>1) - x[13];
 173
 174       y[2] = a00 + a30;
 175       y[6] = a00 - a30;
 176       y[3] = a20 - a10;
 177       y[7] = a20 + a10;
 178
 179       a00 = (x[2] + x[10])>>1;
 180       a10 =  x[6] + x[14];
 181       a20 = (x[3] + x[11])>>1;
 182       a30 =  x[7] + x[15];
 183
 184       y[8]  = a00 + (a10>>1);
 185       y[12] = a00 - (a10>>1);
 186       y[9]  = a20 + (a30>>1);
 187       y[13] = a20 - (a30>>1);
 188
 189       a00 = a00      - x[10];
 190       a10 = (a10>>1) - x[14];
 191       a20 = a20      - x[11];
 192       a30 = (a30>>1) - x[15];
 193
 194       y[10] = a00 + a30;
 195       y[14] = a00 - a30;
 196       y[11] = a20 - a10;
 197       y[15] = a20 + a10;
 198
 199       FIXP_DBL vr, vi, ur, ui;
 200
 201       ur = y[0]>>1;
 202       ui = y[1]>>1;
 203       vr = y[8];
 204       vi = y[9];
 205       x[0] = ur + (vr>>1);
 206       x[1] = ui + (vi>>1);
 207       x[8] = ur - (vr>>1);
 208       x[9] = ui - (vi>>1);
 209
 210       ur = y[4]>>1;
 211       ui = y[5]>>1;
 212       vi = y[12];
 213       vr = y[13];
 214       x[4]  = ur + (vr>>1);
 215       x[5]  = ui - (vi>>1);
 216       x[12] = ur - (vr>>1);
 217       x[13] = ui + (vi>>1);
 218
 219       ur = y[10];
 220       ui = y[11];
 221       vr = fMultDiv2(ui+ur,W_PiFOURTH);
 222       vi = fMultDiv2(ui-ur,W_PiFOURTH);
 223       ur = y[2];
 224       ui = y[3];
 225       x[2]  = (ur>>1) + vr;
 226       x[3]  = (ui>>1) + vi;
 227       x[10] = (ur>>1) - vr;
 228       x[11] = (ui>>1) - vi;
 229
 230       ur = y[14];
 231       ui = y[15];
 232       vr = fMultDiv2(ui-ur,W_PiFOURTH);
 233       vi = fMultDiv2(ui+ur,W_PiFOURTH);
 234       ur = y[6];
 235       ui = y[7];
 236       x[6]  = (ur>>1) + vr;
 237       x[7]  = (ui>>1) - vi;
 238       x[14] = (ur>>1) - vr;
 239       x[15] = (ui>>1) + vi;
 240 }
 241
 242 /**
 243  * \brief FFT of fixed length 16
 244  */
 245 inline void fft_16(FIXP_DBL *x);
 246
 247 /**
 248  * \brief FFT of fixed length 32
 249  */
 250 inline void fft_32(FIXP_DBL *x);
 251
 252
 253 #endif