Major update

[dttsp.git] / jDttSP / wscompand.c

diff --git a/jDttSP/wscompand.c b/jDttSP/wscompand.c
new file mode 100644 (file)
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+++ b/jDttSP/wscompand.c
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+// wscompand.c
+// waveshaping compander, mostly for speech
+/*
+This file is part of a program that implements a Software-Defined Radio.
+
+Copyright (C) 2004-2005 by Frank Brickle, AB2KT and Bob McGwier, N4HY
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+The authors can be reached by email at
+
+ab2kt@arrl.net
+or
+rwmcgwier@comcast.net
+
+or by paper mail at
+
+The DTTS Microwave Society
+6 Kathleen Place
+Bridgewater, NJ 08807
+*/
+
+#include <wscompand.h>
+
+PRIVATE INLINE REAL
+WSCLookup(WSCompander wsc, REAL x) {
+  if (x > 0.0) {
+    REAL d = x - (int) x, y, *tbl = wsc->tbl;
+    int i = (int) (x * wsc->npts), end = wsc->nend;
+    if (i < end)
+      y = tbl[i] + d * (tbl[i + 1] - tbl[i]);
+    else
+      y = tbl[end];
+    return y / x;
+  } else
+    return 0.0;
+}
+
+void
+WSCompand(WSCompander wsc) {
+  int i, n = CXBsize(wsc->buff);
+  for (i = 0; i < n; i++) {
+    COMPLEX val = CXBdata(wsc->buff, i);
+    REAL mag = Cmag(val),
+         scl = WSCLookup(wsc, mag);
+    CXBdata(wsc->buff, i) = Cscl(val, scl);
+  }
+}
+
+void
+WSCReset(WSCompander wsc, REAL fac) {
+  int i;
+  REAL *tbl = wsc->tbl;
+
+  if (fac == 0.0)      // just linear
+    for (i = 0; i < wsc->npts; i++)
+      tbl[i] = i / (REAL) wsc->npts;
+
+  else {               // exponential
+    REAL del = fac / wsc->nend,
+         scl = 1.0 - exp(fac);
+    for (i = 0; i < wsc->npts; i++)
+      tbl[i] = (1.0 - exp(i * del)) / scl;
+  }
+
+  wsc->fac = fac;
+}
+
+// fac < 0: compression
+// fac > 0: expansion
+
+WSCompander
+newWSCompander(int npts,
+              REAL fac,
+              CXB buff) {
+  WSCompander wsc;
+
+  wsc = (WSCompander) safealloc(1,
+                               sizeof(WSCompanderInfo),
+                               "WSCompander struct");
+  wsc->npts = npts;
+  wsc->nend = npts - 1;
+  wsc->tbl = newvec_REAL(npts, "WSCompander table");
+  wsc->buff = newCXB(npts, CXBbase(buff), "WSCompander buff");
+  WSCReset(wsc, fac);
+  return wsc;
+}
+
+void
+delWSCompander(WSCompander wsc) {
+  if (wsc) {
+    delvec_REAL(wsc->tbl);
+    delCXB(wsc->buff);
+    safefree((char *) wsc);
+  }
+}