From ca07a9833149d270d1e5b44cfa381ac6ac03e39c Mon Sep 17 00:00:00 2001
From: Benny Prijono <bennylp@teluu.com>
Date: Sat, 7 Apr 2007 14:53:15 +0000
Subject: Moved resample to third_party directory

git-svn-id: http://svn.pjsip.org/repos/pjproject/branches/split-3rd-party@1170 74dad513-b988-da41-8d7b-12977e46ad98
---
 third_party/resample/src/windowfilter.c | 114 ++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 third_party/resample/src/windowfilter.c

(limited to 'third_party/resample/src/windowfilter.c')

diff --git a/third_party/resample/src/windowfilter.c b/third_party/resample/src/windowfilter.c
new file mode 100644
index 00000000..b2b67690
--- /dev/null
+++ b/third_party/resample/src/windowfilter.c
@@ -0,0 +1,114 @@
+/* makefilter.c */
+
+#include <stdio.h>
+#include <math.h>
+#include "stdefs.h"
+#include "filterkit.h"
+#include "resample.h"
+#define MAXNWING   8192		/* FIXME: flush */
+
+/* LIBRARIES needed:
+ *
+ * 1. filterkit
+ *       makeFilter()  - designs a Kaiser-windowed low-pass filter
+ *       writeFilter() - writes a filter to a standard filter file
+ *       GetUShort()   - prompt user for a UHWORD with help
+ *       GetDouble()   - prompt user for a double with help
+ *
+ * 2. math
+ */
+
+char NmultHelp[] =
+    "\n   Nmult is the length of the symmetric FIR lowpass filter used"
+    "\n   by the sampling rate converter. It must be odd."
+    "\n   This is the number of multiplies per output sample for"
+    "\n   up-conversions (Factor>1), and is the number of multiplies"
+    "\n   per input sample for down-conversions (Factor<1). Thus if"
+    "\n   the rate conversion is Srate2 = Factor*Srate1, then you have"
+    "\n   Nmult*Srate1*MAXof(Factor,1) multiplies per second of real time."
+    "\n   Naturally, higher Nmult gives better lowpass-filtering at the"
+    "\n   expense of longer compute times. Nmult should be odd because"
+    "\n   it is the length of a symmetric FIR filter, and the current"
+    "\n   implementation requires a coefficient at the time origin.\n";      
+
+char FrollHelp[] =
+    "\n   Froll determines the frequency at which the lowpass filter begins to"
+    "\n   roll-off. If Froll=1, then there is no 'guard zone' and the filter"
+    "\n   roll-off region will be aliased. If Froll is 0.90, for example, then"
+    "\n   the filter begins rolling off at 0.90*Srate/2, so that by Srate/2,"
+    "\n   the filter is well down and aliasing is reduced.  Since aliasing"
+    "\n   distortion is typically worse than loss of the high-frequency spectral"
+    "\n   amplitude, Froll<1 is highly recommended. The default of 0.90"
+    "\n   sacrifices the upper 10 percent of the spectrum as an anti-aliasing"
+    "\n   guard zone.\n";
+
+char BetaHelp[] =
+    "\n   Beta trades the rejection of the lowpass filter against the"
+    "\n   transition width from passband to stopband. Larger Beta means"
+    "\n   a slower transition and greater stopband rejection. See Rabiner"
+    "\n   and Gold (Th. and App. of DSP) under Kaiser windows for more about"
+    "\n   Beta. The following table from Rabiner and Gold (p. 101) gives some"
+    "\n   feel for the effect of Beta:"
+    "\n"
+    "\n               BETA    D       PB RIP   SB RIP"
+    "\n               2.120   1.50  +-0.27      -30"
+    "\n               3.384   2.23    0.0864    -40"
+    "\n               4.538   2.93    0.0274    -50"
+    "\n               5.658   3.62    0.00868   -60"
+    "\n               6.764   4.32    0.00275   -70"
+    "\n               7.865   5.0     0.000868  -80"
+    "\n               8.960   5.7     0.000275  -90"
+    "\n               10.056  6.4     0.000087  -100"
+   "\n"
+   "\n   Above, ripples are in dB, and the transition band width is "
+   "\n   approximately D*Fs/N, where Fs = sampling rate, "
+   "\n   and N = window length.  PB = 'pass band' and SB = 'stop band'."
+   "\n   Alternatively, D is the transition widths in bins given a"
+   "\n   length N DFT (i.e. a window transform with no zero padding."
+   "\n";
+
+
+int main(void)
+{
+   HWORD Imp[MAXNWING];               /* Filter coefficients */
+   HWORD ImpD[MAXNWING];              /* ImpD[i] = ImpD[i+1] - ImpD[i] */
+   double Froll, Beta;
+   UHWORD Nmult, Nwing, LpScl;
+   int err;
+
+   Froll = 0.90;
+   Beta  = 9;
+   Nmult = 65;
+   while (1)
+      {
+      Froll = GetDouble("Normalized Roll-off freq (0<Froll<=1)",
+         Froll, FrollHelp);
+      Beta = GetDouble("Beta", Beta, BetaHelp);
+      Nmult = GetUHWORD("Odd filter length 'Nmult'", Nmult, NmultHelp);
+      if ((Nmult&1) == 0) {
+	  Nmult++;
+	  printf("Filter length increased to %d to make it odd.\n",Nmult);
+      }
+      Nwing = Npc*(Nmult-1)/2;   /* # of filter coeffs in right wing */
+      printf("\n");
+      if (!(Nmult % 2))
+	  printf("Error: Nmult must be odd and greater than zero\n");
+      else if ((err = makeFilter(Imp, ImpD, &LpScl, Nwing, Froll, Beta))) {
+	  printf("*** Error: Unable to make filter.\n");
+	  if (err == 1)
+	      printf("\tNmult=%d too large for MAXNWING=%d\n",Nmult,MAXNWING);
+	  else if (err == 2)
+	      printf("\tNormalized roll-off freq Froll must be between 0 and 1\n");
+	  else if (err == 3)
+	      printf("\tHeisenberg says Beta must be greater or equal to 1\n");
+	  else if (err == 4) {
+	      printf("\tUnity-gain scale factor overflows 16-bit half-word\n");
+	      printf("\tFilter design was probably way off. Try relaxing specs.\n");
+	  }
+      } else if ((err = writeFilter(Imp, ImpD, LpScl, Nmult, Nwing)))
+	  printf("Error: Unable to write filter, err=%d\n", err);
+      else
+	  break;
+  }
+   return(0);
+}
-- 
cgit v1.2.3