Alc/uhjfilter.c

   1
   2 #include "config.h"
   3
   4 #include "alu.h"
   5 #include "uhjfilter.h"
   6
   7 /* This is the maximum number of samples processed for each inner loop
   8  * iteration. */
   9 #define MAX_UPDATE_SAMPLES  256
  10
  11
  12 static const ALfloat Filter1Coeff[4] = {
  13     0.6923878f, 0.9360654322959f, 0.9882295226860f, 0.9987488452737f
  14 };
  15 static const ALfloat Filter2Coeff[4] = {
  16     0.4021921162426f, 0.8561710882420f, 0.9722909545651f, 0.9952884791278f
  17 };
  18
  19 void EncodeUhj2(Uhj2Encoder *enc, ALfloat (*restrict OutBuffer)[BUFFERSIZE], ALfloat (*restrict InSamples)[BUFFERSIZE], ALuint SamplesToDo)
  20 {
  21     ALuint base, i, c;
  22
  23     for(base = 0;base < SamplesToDo;)
  24     {
  25         ALfloat D[MAX_UPDATE_SAMPLES], S;
  26         ALuint todo = minu(SamplesToDo - base, MAX_UPDATE_SAMPLES);
  27
  28         /* D = 0.6554516*Y */
  29         for(i = 0;i < todo;i++)
  30         {
  31             ALfloat in = 0.6554516f*InSamples[2][base+i];
  32             for(c = 0;c < 4;c++)
  33             {
  34                 ALfloat aa = Filter1Coeff[c]*Filter1Coeff[c];
  35                 ALfloat out = aa*(in + enc->Filter1_Y[c].y[1]) - enc->Filter1_Y[c].x[1];
  36                 enc->Filter1_Y[c].x[1] = enc->Filter1_Y[c].x[0];
  37                 enc->Filter1_Y[c].x[0] = in;
  38                 enc->Filter1_Y[c].y[1] = enc->Filter1_Y[c].y[0];
  39                 enc->Filter1_Y[c].y[0] = out;
  40                 in = out;
  41             }
  42             /* NOTE: Filter1 requires a 1 sample delay for the base output, so
  43              * take the sample before the last for output.
  44              */
  45             D[i] = enc->Filter1_Y[3].y[1];
  46         }
  47
  48         /* D += j(-0.3420201*W' + 0.5098604*X) */
  49         for(i = 0;i < todo;i++)
  50         {
  51             ALfloat in = -0.3420201f*1.414213562f*InSamples[0][base+i] +
  52                           0.5098604f*InSamples[1][base+i];
  53             for(c = 0;c < 4;c++)
  54             {
  55                 ALfloat aa = Filter2Coeff[c]*Filter2Coeff[c];
  56                 ALfloat out = aa*(in + enc->Filter2_WX[c].y[1]) - enc->Filter2_WX[c].x[1];
  57                 enc->Filter2_WX[c].x[1] = enc->Filter2_WX[c].x[0];
  58                 enc->Filter2_WX[c].x[0] = in;
  59                 enc->Filter2_WX[c].y[1] = enc->Filter2_WX[c].y[0];
  60                 enc->Filter2_WX[c].y[0] = out;
  61                 in = out;
  62             }
  63             D[i] += enc->Filter2_WX[3].y[0];
  64         }
  65
  66         /* S = 0.9396926*W' + 0.1855740*X
  67          * Left = (S + D)/2.0
  68          * Right = (S - D)/2.0
  69          */
  70         for(i = 0;i < todo;i++)
  71         {
  72             ALfloat in = 0.9396926f*1.414213562f*InSamples[0][base+i] +
  73                          0.1855740f*InSamples[1][base+i];
  74             for(c = 0;c < 4;c++)
  75             {
  76                 ALfloat aa = Filter1Coeff[c]*Filter1Coeff[c];
  77                 ALfloat out = aa*(in + enc->Filter1_WX[c].y[1]) - enc->Filter1_WX[c].x[1];
  78                 enc->Filter1_WX[c].x[1] = enc->Filter1_WX[c].x[0];
  79                 enc->Filter1_WX[c].x[0] = in;
  80                 enc->Filter1_WX[c].y[1] = enc->Filter1_WX[c].y[0];
  81                 enc->Filter1_WX[c].y[0] = out;
  82                 in = out;
  83             }
  84             S = enc->Filter1_WX[3].y[1];
  85             OutBuffer[0][base + i] += (S + D[i]) * 0.5f;
  86             OutBuffer[1][base + i] += (S - D[i]) * 0.5f;
  87         }
  88
  89         base += todo;
  90     }
  91 }