Adding new audio output filter layer libaf

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@7569 b3059339-0415-0410-9bf9-f77b7e298cf2

1 files changed, 203 insertions, 0 deletions

diff --git a/libaf/window.c b/libaf/window.c
new file mode 100644
index 0000000000..25b92bc313
--- /dev/null
+++ b/libaf/window.c
@@ -0,0 +1,203 @@
+/*=============================================================================
+//	
+//  This software has been released under the terms of the GNU Public
+//  license. See http://www.gnu.org/copyleft/gpl.html for details.
+//
+//  Copyright 2001 Anders Johansson ajh@atri.curtin.edu.au
+//
+//=============================================================================
+*/
+
+/* Calculates a number of window functions. The following window
+   functions are currently implemented: Boxcar, Triang, Hanning,
+   Hamming, Blackman, Flattop and Kaiser. In the function call n is
+   the number of filter taps and w the buffer in which the filter
+   coefficients will be stored.
+*/
+
+#include <math.h>
+#include "dsp.h"
+
+/*
+// Boxcar
+//
+// n window length
+// w buffer for the window parameters
+*/
+void boxcar(int n, _ftype_t* w)
+{
+  int i;
+  // Calculate window coefficients
+  for (i=0 ; i<n ; i++)
+    w[i] = 1.0;
+}
+
+
+/*
+// Triang a.k.a Bartlett
+//
+//               |    (N-1)| 
+//           2 * |k - -----|
+//               |      2  |
+// w = 1.0 - ---------------
+//                    N+1
+// n window length
+// w buffer for the window parameters
+*/
+void triang(int n, _ftype_t* w)
+{
+  _ftype_t k1  = (_ftype_t)(n & 1);
+  _ftype_t k2  = 1/((_ftype_t)n + k1);
+  int      end = (n + 1) >> 1;
+  int	   i;
+  
+  // Calculate window coefficients
+  for (i=0 ; i<end ; i++)
+    w[i] = w[n-i-1] = (2.0*((_ftype_t)(i+1))-(1.0-k1))*k2;
+}
+
+
+/*
+// Hanning
+//                   2*pi*k
+// w = 0.5 - 0.5*cos(------), where 0 < k <= N
+//                    N+1
+// n window length
+// w buffer for the window parameters
+*/
+void hanning(int n, _ftype_t* w)
+{
+  int	   i;
+  _ftype_t k = 2*M_PI/((_ftype_t)(n+1)); // 2*pi/(N+1)
+  
+  // Calculate window coefficients
+  for (i=0; i<n; i++)
+    *w++ = 0.5*(1.0 - cos(k*(_ftype_t)(i+1)));
+}
+
+/*
+// Hamming
+//                        2*pi*k
+// w(k) = 0.54 - 0.46*cos(------), where 0 <= k < N
+//                         N-1
+//
+// n window length
+// w buffer for the window parameters
+*/
+void hamming(int n,_ftype_t* w)
+{
+  int      i;
+  _ftype_t k = 2*M_PI/((_ftype_t)(n-1)); // 2*pi/(N-1)
+
+  // Calculate window coefficients
+  for (i=0; i<n; i++)
+    *w++ = 0.54 - 0.46*cos(k*(_ftype_t)i);
+}
+
+/*
+// Blackman
+//                       2*pi*k             4*pi*k
+// w(k) = 0.42 - 0.5*cos(------) + 0.08*cos(------), where 0 <= k < N
+//                        N-1                 N-1
+//
+// n window length
+// w buffer for the window parameters
+*/
+void blackman(int n,_ftype_t* w)
+{
+  int      i;
+  _ftype_t k1 = 2*M_PI/((_ftype_t)(n-1)); // 2*pi/(N-1)
+  _ftype_t k2 = 2*k1; // 4*pi/(N-1)
+
+  // Calculate window coefficients
+  for (i=0; i<n; i++)
+    *w++ = 0.42 - 0.50*cos(k1*(_ftype_t)i) + 0.08*cos(k2*(_ftype_t)i);
+}
+
+/*
+// Flattop
+//                                        2*pi*k                     4*pi*k
+// w(k) = 0.2810638602 - 0.5208971735*cos(------) + 0.1980389663*cos(------), where 0 <= k < N
+//                                          N-1                        N-1
+//
+// n window length
+// w buffer for the window parameters
+*/
+void flattop(int n,_ftype_t* w)
+{
+  int      i;
+  _ftype_t k1 = 2*M_PI/((_ftype_t)(n-1)); // 2*pi/(N-1)
+  _ftype_t k2 = 2*k1;                   // 4*pi/(N-1)
+  
+  // Calculate window coefficients
+  for (i=0; i<n; i++)
+    *w++ = 0.2810638602 - 0.5208971735*cos(k1*(_ftype_t)i) + 0.1980389663*cos(k2*(_ftype_t)i);
+}
+
+/* Computes the 0th order modified Bessel function of the first kind.  
+// (Needed to compute Kaiser window) 
+//   
+// y = sum( (x/(2*n))^2 )
+//      n
+*/
+#define BIZ_EPSILON 1E-21 // Max error acceptable 
+
+_ftype_t besselizero(_ftype_t x)
+{ 
+  _ftype_t temp;
+  _ftype_t sum   = 1.0;
+  _ftype_t u     = 1.0;
+  _ftype_t halfx = x/2.0;
+  int      n     = 1;
+
+  do {
+    temp = halfx/(_ftype_t)n;
+    u *=temp * temp;
+    sum += u;
+    n++;
+  } while (u >= BIZ_EPSILON * sum);
+  return(sum);
+}
+
+/*
+// Kaiser
+//
+// n window length
+// w buffer for the window parameters
+// b beta parameter of Kaiser window, Beta >= 1
+//
+// Beta trades the rejection of the low pass filter against the
+// transition width from passband to stop band.  Larger Beta means a
+// slower transition and greater stop band rejection.  See Rabiner and
+// Gold (Theory and Application of DSP) under Kaiser windows for more
+// about Beta.  The following table from Rabiner and Gold gives some
+// feel for the effect of Beta:
+// 
+// All ripples in dB, width of transition band = D*N where N = window
+// length
+// 
+// BETA    D       PB RIP   SB RIP
+// 2.120   1.50  +-0.27      -30
+// 3.384   2.23    0.0864    -40
+// 4.538   2.93    0.0274    -50
+// 5.658   3.62    0.00868   -60
+// 6.764   4.32    0.00275   -70
+// 7.865   5.0     0.000868  -80
+// 8.960   5.7     0.000275  -90
+// 10.056  6.4     0.000087  -100
+*/
+void kaiser(int n, _ftype_t* w, _ftype_t b)
+{
+  _ftype_t tmp;
+  _ftype_t k1  = 1.0/besselizero(b);
+  int	   k2  = 1 - (n & 1);
+  int      end = (n + 1) >> 1;
+  int      i; 
+  
+  // Calculate window coefficients
+  for (i=0 ; i<end ; i++){
+    tmp = (_ftype_t)(2*i + k2) / ((_ftype_t)n - 1.0);
+    w[end-(1&(!k2))+i] = w[end-1-i] = k1 * besselizero(b*sqrt(1.0 - tmp*tmp));
+  }
+}
+