134 lines
3.3 KiB
C#
134 lines
3.3 KiB
C#
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/* csvorbis
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* Copyright (C) 2000 ymnk, JCraft,Inc.
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*
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* Written by: 2000 ymnk<ymnk@jcraft.com>
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* Ported to C# from JOrbis by: Mark Crichton <crichton@gimp.org>
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*
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* Thanks go to the JOrbis team, for licencing the code under the
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* LGPL, making my job a lot easier.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public License
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* as published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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using System;
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using System.Runtime.InteropServices;
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using csogg;
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namespace csvorbis
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{
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/*
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function: LSP (also called LSF) conversion routines
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The LSP generation code is taken (with minimal modification) from
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"On the Computation of the LSP Frequencies" by Joseph Rothweiler
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<rothwlr@altavista.net>, available at:
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http://www2.xtdl.com/~rothwlr/lsfpaper/lsfpage.html
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********************************************************************/
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class Lsp
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{
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[StructLayout(LayoutKind.Explicit, Size=32, CharSet=CharSet.Ansi)]
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struct FloatHack
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{
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[FieldOffset(0)] public float fh_float;
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[FieldOffset(0)] public int fh_int;
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}
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static float M_PI=(float)(3.1415926539);
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internal static void lsp_to_curve(float[] curve,
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int[] map, int n, int ln,
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float[] lsp, int m,
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float amp, float ampoffset)
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{
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int i;
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float wdel=M_PI/ln;
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for(i=0;i<m;i++)lsp[i]=Lookup.coslook(lsp[i]);
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int m2=(m/2)*2;
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i=0;
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while(i<n)
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{
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FloatHack fh = new FloatHack();
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int k=map[i];
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float p=.7071067812f;
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float q=.7071067812f;
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float w=Lookup.coslook(wdel*k);
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//int ftmp=0;
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int c=(int)((uint)m >> 1);
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for(int j=0;j<m2;j+=2)
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{
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q*=lsp[j]-w;
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p*=lsp[j+1]-w;
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}
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if((m&1)!=0)
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{
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/* odd order filter; slightly assymetric */
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/* the last coefficient */
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q*=lsp[m-1]-w;
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q*=q;
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p*=p*(1.0f-w*w);
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}
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else
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{
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/* even order filter; still symmetric */
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q*=q*(1.0f+w);
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p*=p*(1.0f-w);
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}
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// q=frexp(p+q,&qexp);
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q=p+q;
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fh.fh_float = q;
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int hx=fh.fh_int;
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int ix=0x7fffffff&hx;
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int qexp=0;
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if(ix>=0x7f800000||(ix==0))
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{
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// 0,inf,nan
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}
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else
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{
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if(ix<0x00800000)
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{ // subnormal
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q*=3.3554432000e+07F; // 0x4c000000
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fh.fh_float = q;
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hx=fh.fh_int;
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ix=0x7fffffff&hx;
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qexp=-25;
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}
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qexp += (int)(((uint)ix >> 23)-126);
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hx=(int)((hx&0x807fffff)|0x3f000000);
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fh.fh_int = hx;
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q=fh.fh_float;
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}
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q=Lookup.fromdBlook(amp*
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Lookup.invsqlook(q)*
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Lookup.invsq2explook(qexp+m)-ampoffset);
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do{curve[i]*=q; i++;}
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// do{curve[i++]=q;}
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while(i<n&&map[i]==k);
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}
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}
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}
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}
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