text: /*
   * Atrac common functions
   * Copyright (c) 2006-2008 Maxim Poliakovski
   * Copyright (c) 2006-2008 Benjamin Larsson
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg 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
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  /**
   * @file
   */
  
  #include <math.h>
  #include <stddef.h>
  #include <stdio.h>
  #include <string.h>
  
  #include "avcodec.h"
  #include "atrac.h"
  
  float ff_atrac_sf_table[64];
  static float qmf_window[48];
  
  static const float qmf_48tap_half[24] = {
     -0.00001461907, -0.00009205479,-0.000056157569,0.00030117269,
      0.0002422519,  -0.00085293897,-0.0005205574,  0.0020340169,
      0.00078333891, -0.0042153862, -0.00075614988, 0.0078402944,
     -0.000061169922,-0.01344162,    0.0024626821,  0.021736089,
     -0.007801671,   -0.034090221,   0.01880949,    0.054326009,
     -0.043596379,   -0.099384367,   0.13207909,    0.46424159
  };
  
  /**
   * Generate common tables
   */
  
  void ff_atrac_generate_tables(void)
  {
      int i;
      float s;
  
      /* Generate scale factors */
      if (!ff_atrac_sf_table[63])
          for (i=0 ; i<64 ; i++)
              ff_atrac_sf_table[i] = pow(2.0, (i - 15) / 3.0);
  
      /* Generate the QMF window. */
      if (!qmf_window[47])
          for (i=0 ; i<24; i++) {
              s = qmf_48tap_half[i] * 2.0;
              qmf_window[i] = qmf_window[47 - i] = s;
          }
  }
  
  
  /**
   * Quadrature mirror synthesis filter.
   *
   * @param inlo      lower part of spectrum
   * @param inhi      higher part of spectrum
   * @param nIn       size of spectrum buffer
   * @param pOut      out buffer
   * @param delayBuf  delayBuf buffer
   * @param temp      temp buffer
   */
  
  
  void ff_atrac_iqmf (float *inlo, float *inhi, unsigned int nIn, float *pOut, float *delayBuf, float *temp)
  {
      int   i, j;
      float   *p1, *p3;
  
      memcpy(temp, delayBuf, 46*sizeof(float));
  
      p3 = temp + 46;
  
      /* loop1 */
      for(i=0; i<nIn; i+=2){
          p3[2*i+0] = inlo[i  ] + inhi[i  ];
          p3[2*i+1] = inlo[i  ] - inhi[i  ];
          p3[2*i+2] = inlo[i+1] + inhi[i+1];
          p3[2*i+3] = inlo[i+1] - inhi[i+1];
      }
  
      /* loop2 */
      p1 = temp;
      for (j = nIn; j != 0; j--) {
          float s1 = 0.0;
          float s2 = 0.0;
  
          for (i = 0; i < 48; i += 2) {
              s1 += p1[i] * qmf_window[i];
              s2 += p1[i+1] * qmf_window[i+1];
          }
  
          pOut[0] = s2;
          pOut[1] = s1;
  
          p1 += 2;
          pOut += 2;
      }
  
      /* Update the delay buffer. */
      memcpy(delayBuf, temp + nIn*2, 46*sizeof(float));
  }
  