gst/modplug/libmodplug/snd_flt.cpp

   1 /*
   2  * This source code is public domain.
   3  *
   4  * Authors: Olivier Lapicque <olivierl@jps.net>
   5 */
   6
   7 #ifdef HAVE_CONFIG_H
   8 #include "config.h"
   9 #endif
  10
  11 #include "stdafx.h"
  12 #include "sndfile.h"
  13
  14 // AWE32: cutoff = reg[0-255] * 31.25 + 100 -> [100Hz-8060Hz]
  15 // EMU10K1 docs: cutoff = reg[0-127]*62+100
  16 #define FILTER_PRECISION        8192
  17
  18 #ifndef NO_FILTER
  19
  20 #ifdef MSC_VER
  21 #define _ASM_MATH
  22 #endif
  23
  24 #ifdef _ASM_MATH
  25
  26 // pow(a,b) returns a^^b -> 2^^(b.log2(a))
  27 static float pow(float a, float b)
  28 {
  29         long tmpint;
  30         float result;
  31         _asm {
  32         fld b                           // Load b
  33         fld a                           // Load a
  34         fyl2x                           // ST(0) = b.log2(a)
  35         fist tmpint                     // Store integer exponent
  36         fisub tmpint            // ST(0) = -1 <= (b*log2(a)) <= 1
  37         f2xm1                           // ST(0) = 2^(x)-1
  38         fild tmpint                     // load integer exponent
  39         fld1                            // Load 1
  40         fscale                          // ST(0) = 2^ST(1)
  41         fstp ST(1)                      // Remove the integer from the stack
  42         fmul ST(1), ST(0)       // multiply with fractional part
  43         faddp ST(1), ST(0)      // add integer_part
  44         fstp result                     // Store the result
  45         }
  46         return result;
  47 }
  48
  49
  50 #else
  51
  52 #include <math.h>
  53
  54 #endif // _ASM_MATH
  55
  56
  57 DWORD CSoundFile::CutOffToFrequency(UINT nCutOff, int flt_modifier) const
  58 //-----------------------------------------------------------------------
  59 {
  60         float Fc;
  61
  62         if (m_dwSongFlags & SONG_EXFILTERRANGE)
  63                 Fc = 110.0f * pow(2.0f, 0.25f + ((float)(nCutOff*(flt_modifier+256)))/(21.0f*512.0f));
  64         else
  65                 Fc = 110.0f * pow(2.0f, 0.25f + ((float)(nCutOff*(flt_modifier+256)))/(24.0f*512.0f));
  66         LONG freq = (LONG)Fc;
  67         if (freq < 120) return 120;
  68         if (freq > 10000) return 10000;
  69         if (freq*2 > (LONG)gdwMixingFreq) freq = gdwMixingFreq>>1;
  70         return (DWORD)freq;
  71 }
  72
  73
  74 // Simple 2-poles resonant filter
  75 void CSoundFile::SetupChannelFilter(MODCHANNEL *pChn, BOOL bReset, int flt_modifier) const
  76 //----------------------------------------------------------------------------------------
  77 {
  78         float fc = (float)CutOffToFrequency(pChn->nCutOff, flt_modifier);
  79         float fs = (float)gdwMixingFreq;
  80         float fg, fb0, fb1;
  81
  82         fc *= (float)(2.0*3.14159265358/fs);
  83         float dmpfac = pow(10.0f, -((24.0f / 128.0f)*(float)pChn->nResonance) / 20.0f);
  84         float d = (1.0f-2.0f*dmpfac)* fc;
  85         if (d>2.0) d = 2.0;
  86         d = (2.0f*dmpfac - d)/fc;
  87         float e = pow(1.0f/fc, 2);
  88
  89         fg=1/(1+d+e);
  90         fb0=(d+e+e)/(1+d+e);
  91         fb1=-e/(1+d+e);
  92
  93         pChn->nFilter_A0 = (int)(fg * FILTER_PRECISION);
  94         pChn->nFilter_B0 = (int)(fb0 * FILTER_PRECISION);
  95         pChn->nFilter_B1 = (int)(fb1 * FILTER_PRECISION);
  96
  97         if (bReset)
  98         {
  99                 pChn->nFilter_Y1 = pChn->nFilter_Y2 = 0;
 100                 pChn->nFilter_Y3 = pChn->nFilter_Y4 = 0;
 101         }
 102         pChn->dwFlags |= CHN_FILTER;
 103 }
 104
 105 #endif // NO_FILTER