1 files changed, 127 insertions, 0 deletions
diff --git a/apps/dither.cc b/apps/dither.cc
new file mode 100644
index 0000000..c85b296
--- /dev/null
+++ b/apps/dither.cc
@@ -0,0 +1,127 @@
+// -------------------------------------------------------------------------
+//
+//    Copyright (C) 2010-2014 Fons Adriaensen <fons@linuxaudio.org>
+//    
+//    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., 675 Mass Ave, Cambridge, MA 02139, USA.
+//
+// -------------------------------------------------------------------------
+
+
+#include <string.h>
+#include <math.h>
+#include "dither.h"
+
+
+float Dither::_div = 0;
+
+#define SCALE 32768.0f
+#define LIMIT 32767
+
+
+
+Dither::Dither (void)
+{
+    reset ();
+    _div = ldexpf (1.0f, 32);
+}
+
+
+void Dither::reset (void)
+{
+    memset (_err, 0, (SIZE + 4) * sizeof(float));
+    _ind = SIZE - 1;
+    _ran = 1234567;
+}
+
+
+void Dither::proc_rectangular (int nsam, const float *srce, int16_t *dest, int ds, int dd)
+{
+    float   v, r;
+    int16_t k;
+
+    while (nsam--)
+    {
+	r = genrand () - 0.5f;
+        v = *srce * SCALE + r;
+	k = lrintf (v);
+	if      (k < -LIMIT) k = -LIMIT;
+	else if (k >  LIMIT) k =  LIMIT;
+        *dest = k;
+        srce += ds;
+        dest += dd;
+    }
+}
+
+
+void Dither::proc_triangular (int nsam, const float *srce, int16_t *dest, int ds, int dd)
+{
+    float   v, r0, r1;
+    int16_t k;
+
+    r1 = *_err;
+    while (nsam--)
+    {
+        r0 = genrand ();
+        v = *srce * SCALE + r0 - r1;
+	r1 = r0;
+	k = lrintf (v);
+	if      (k < -LIMIT) k = -LIMIT;
+	else if (k >  LIMIT) k =  LIMIT;
+        *dest = k;
+        srce += ds;
+        dest += dd;
+    }
+    *_err = r1;
+}
+
+
+void Dither::proc_lipschitz (int nsam, const float *srce, int16_t *dest, int ds, int dd)
+{
+    float   e, u, v, *p;
+    int     i;
+    int16_t k;
+
+    i = _ind;
+    while (nsam--)
+    {
+	p = _err + i;
+        u = *srce * SCALE
+	    - 2.033f * p [0]
+	    + 2.165f * p [1]
+	    - 1.959f * p [2]
+	    + 1.590f * p [3]
+	    - 0.615f * p [4];
+	v = u + genrand () - genrand ();
+	k = lrintf (v);
+	e = k - u;
+	if      (k < -LIMIT) k = -LIMIT;
+	else if (k >  LIMIT) k =  LIMIT;
+        *dest = k;
+	if (--i < 0)
+	{
+	    _err [SIZE + 0] = _err [0];
+	    _err [SIZE + 1] = _err [1];
+	    _err [SIZE + 2] = _err [2];
+	    _err [SIZE + 3] = _err [3];
+	    i += SIZE;
+	}
+	_err [i] = e;
+        srce += ds;
+        dest += dd;
+    }
+    _ind = i;
+}
+
+