Update of /cvsroot/audacity/audacity-src/src
In directory sc8-pr-cvs11.sourceforge.net:/tmp/cvs-serv22387/src
Modified Files:
Dither.cpp
Log Message:
Corrected pdf of triangle and shaped dithers.
Index: Dither.cpp
===================================================================
RCS file: /cvsroot/audacity/audacity-src/src/Dither.cpp,v
retrieving revision 1.6
retrieving revision 1.7
diff -u -d -r1.6 -r1.7
--- Dither.cpp 15 Jun 2006 14:26:13 -0000 1.6
+++ Dither.cpp 19 Sep 2006 21:37:48 -0000 1.7
@@ -6,7 +6,7 @@
Steve Harris
Markus Meyer
-
+
*******************************************************************//*!
\class Dither
@@ -38,7 +38,7 @@
// Erik de Castro Lopo's header file that
// makes sure that we have lrint and lrintf
// (Note: this file should be included first)
-#include "float_cast.h"
+#include "float_cast.h"
#include <stdlib.h>
#include <math.h>
@@ -166,7 +166,7 @@
if (len == 0)
return; // nothing to do
-
+
if (sourceFormat == destFormat)
{
// No need to dither, because source and destination
@@ -199,7 +199,7 @@
else if (*p < -1.0)
*p = -1.0;
}
- } else
+ } else
if (destFormat == floatSample)
{
// No need to dither, just convert samples to float.
@@ -268,36 +268,36 @@
return sample - DITHER_NOISE;
}
-// Triangle dither
+// Triangle dither - high pass filtered
inline float Dither::TriangleDither(float sample)
{
- float r = DITHER_NOISE * 2.0f - 1.0f;
+ float r = DITHER_NOISE - 0.5f;
float result = sample + r - mTriangleState;
mTriangleState = r;
-
+
return result;
}
// Shaped dither
inline float Dither::ShapedDither(float sample)
{
- float r = DITHER_NOISE * 2.0f - 1.0f;
-
+ // Generate triangular dither, +-1 LSB, flat psd
+ float r = DITHER_NOISE + DITHER_NOISE - 1.0f;
+
// Run FIR
float xe = sample + mBuffer[mPhase] * SHAPED_BS[0]
+ mBuffer[(mPhase - 1) & BUF_MASK] * SHAPED_BS[1]
+ mBuffer[(mPhase - 2) & BUF_MASK] * SHAPED_BS[2]
+ mBuffer[(mPhase - 3) & BUF_MASK] * SHAPED_BS[3]
+ mBuffer[(mPhase - 4) & BUF_MASK] * SHAPED_BS[4];
-
+
// Accumulate FIR and triangular noise
- float result = xe + r - mTriangleState;
- mTriangleState = r;
-
+ float result = xe + r;
+
// Roll buffer and store last error
mPhase = (mPhase + 1) & BUF_MASK;
mBuffer[mPhase] = xe - lrintf(result);
-
+
return result;
}
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