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Lsp.java

/* JOrbis
 * Copyright (C) 2000 ymnk, JCraft,Inc.
 *  
 * Written by: 2000 ymnk<ymnk@jcraft.com>
 *   
 * Many thanks to 
 *   Monty <monty@xiph.org> and 
 *   The XIPHOPHORUS Company http://www.xiph.org/ .
 * JOrbis has been based on their awesome works, Vorbis codec.
 *   
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library 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 Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

package com.jcraft.jorbis;

/*
  function: LSP (also called LSF) conversion routines

  The LSP generation code is taken (with minimal modification) from
  "On the Computation of the LSP Frequencies" by Joseph Rothweiler
  <rothwlr@altavista.net>, available at:
  
  http://www2.xtdl.com/~rothwlr/lsfpaper/lsfpage.html 
 ********************************************************************/

class Lsp{

  static final float M_PI=(float)(3.1415926539);

  static void lsp_to_curve(float[] curve,
                     int[] map, int n, int ln,
                     float[] lsp, int m,
                     float amp, float ampoffset){
    int i;
    float wdel=M_PI/ln;
    for(i=0;i<m;i++)lsp[i]=Lookup.coslook(lsp[i]);
    int m2=(m/2)*2;

    i=0;
    while(i<n){
      int k=map[i];
      float p=.7071067812f;
      float q=.7071067812f;
      float w=Lookup.coslook(wdel*k);
      int ftmp=0;
      int c=m>>>1;

      for(int j=0;j<m2;j+=2){
        q*=lsp[j]-w;
      p*=lsp[j+1]-w;
      }

      if((m&1)!=0){
        /* odd order filter; slightly assymetric */
        /* the last coefficient */
        q*=lsp[m-1]-w;
        q*=q;
        p*=p*(1.f-w*w);
      }
      else{
        /* even order filter; still symmetric */
        q*=q*(1.f+w);
        p*=p*(1.f-w);
      }

      //  q=frexp(p+q,&qexp);
      q=p+q;
      int hx=Float.floatToIntBits(q);
      int ix=0x7fffffff&hx;
      int qexp=0;

      if(ix>=0x7f800000||(ix==0)){
        // 0,inf,nan
      }
      else{
        if(ix<0x00800000){            // subnormal
        q*=3.3554432000e+07;        // 0x4c000000
          hx=Float.floatToIntBits(q);
          ix=0x7fffffff&hx;
        qexp=-25;
        }
        qexp += ((ix>>>23)-126);
        hx=(hx&0x807fffff)|0x3f000000;
        q=Float.intBitsToFloat(hx);
      }

      q=Lookup.fromdBlook(amp*
                    Lookup.invsqlook(q)*
                    Lookup.invsq2explook(qexp+m)-ampoffset);

      do{curve[i++]*=q;}
//    do{curve[i++]=q;}
      while(i<n&&map[i]==k);

    }
  }
}



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