Fixed dither for 64-bit targets.

diff --git a/src/common/pa_dither.c b/src/common/pa_dither.c
index d1d35f1d35c6aa813ea70b416c9c9f7c5e3de382..140e480afbc3469ee5becfecd6b6cf53df3b38d1 100644 (file)
--- a/src/common/pa_dither.c
+++ b/src/common/pa_dither.c
@@ -42,9 +42,14 @@
  @brief Functions for generating dither noise
 */
 
-
-#include "pa_dither.h"
 #include "pa_types.h"
+#include "pa_dither.h"
+
+
+/* Note that the linear congruential algorithm requires 32 bit integers
+ * because it uses arithmetic overflow. So use PaUint32 instead of
+ * unsigned long so it will work on 64 bit systems.
+ */
 
 #define PA_DITHER_BITS_   (15)
 
@@ -57,9 +62,9 @@ void PaUtil_InitializeTriangularDitherState( PaUtilTriangularDitherGenerator *st
 }
 
 
-signed long PaUtil_Generate16BitTriangularDither( PaUtilTriangularDitherGenerator *state )
+PaInt32 PaUtil_Generate16BitTriangularDither( PaUtilTriangularDitherGenerator *state )
 {
-    signed long current, highPass;
+    PaInt32 current, highPass;
 
     /* Generate two random numbers. */
     state->randSeed1 = (state->randSeed1 * 196314165) + 907633515;
@@ -69,9 +74,10 @@ signed long PaUtil_Generate16BitTriangularDither( PaUtilTriangularDitherGenerato
      * Shift before adding to prevent overflow which would skew the distribution.
      * Also shift an extra bit for the high pass filter. 
      */
-#define DITHER_SHIFT_  ((SIZEOF_LONG*8 - PA_DITHER_BITS_) + 1)
-    current = (((signed long)state->randSeed1)>>DITHER_SHIFT_) +
-              (((signed long)state->randSeed2)>>DITHER_SHIFT_);
+#define DITHER_SHIFT_  ((sizeof(PaInt32)*8 - PA_DITHER_BITS_) + 1)
+       
+    current = (((PaInt32)state->randSeed1)>>DITHER_SHIFT_) +
+              (((PaInt32)state->randSeed2)>>DITHER_SHIFT_);
 
     /* High pass filter to reduce audibility. */
     highPass = current - state->previous;
@@ -86,7 +92,7 @@ static const float const_float_dither_scale_ = PA_FLOAT_DITHER_SCALE_;
 
 float PaUtil_GenerateFloatTriangularDither( PaUtilTriangularDitherGenerator *state )
 {
-    signed long current, highPass;
+    PaInt32 current, highPass;
 
     /* Generate two random numbers. */
     state->randSeed1 = (state->randSeed1 * 196314165) + 907633515;
@@ -96,9 +102,8 @@ float PaUtil_GenerateFloatTriangularDither( PaUtilTriangularDitherGenerator *sta
      * Shift before adding to prevent overflow which would skew the distribution.
      * Also shift an extra bit for the high pass filter. 
      */
-#define DITHER_SHIFT_  ((SIZEOF_LONG*8 - PA_DITHER_BITS_) + 1)
-    current = (((signed long)state->randSeed1)>>DITHER_SHIFT_) +
-              (((signed long)state->randSeed2)>>DITHER_SHIFT_);
+    current = (((PaInt32)state->randSeed1)>>DITHER_SHIFT_) +
+              (((PaInt32)state->randSeed2)>>DITHER_SHIFT_);
 
     /* High pass filter to reduce audibility. */
     highPass = current - state->previous;

diff --git a/src/common/pa_dither.h b/src/common/pa_dither.h
index 6776c301136758396e3c73bed97c627ccb533496..12ffc4fc67f00d7c6476b61f21b218f25e466b44 100644 (file)
--- a/src/common/pa_dither.h
+++ b/src/common/pa_dither.h
@@ -44,18 +44,24 @@
  @brief Functions for generating dither noise
 */
 
+#include "pa_types.h"
+
 
 #ifdef __cplusplus
 extern "C"
 {
 #endif /* __cplusplus */
 
+/* Note that the linear congruential algorithm requires 32 bit integers
+ * because it uses arithmetic overflow. So use PaUint32 instead of
+ * unsigned long so it will work on 64 bit systems.
+ */
 
 /** @brief State needed to generate a dither signal */
 typedef struct PaUtilTriangularDitherGenerator{
-    unsigned long previous;
-    unsigned long randSeed1;
-    unsigned long randSeed2;
+    PaUint32 previous;
+    PaUint32 randSeed1;
+    PaUint32 randSeed2;
 } PaUtilTriangularDitherGenerator;
 
 
@@ -73,9 +79,9 @@ void PaUtil_InitializeTriangularDitherState( PaUtilTriangularDitherGenerator *di
     signed short out = (signed short)(((in>>1) + dither) >> 15);
 </pre>
  @return
- A signed long with a range of +32767 to -32768
+ A signed 32-bit integer with a range of +32767 to -32768
 */
-signed long PaUtil_Generate16BitTriangularDither( PaUtilTriangularDitherGenerator *ditherState );
+PaInt32 PaUtil_Generate16BitTriangularDither( PaUtilTriangularDitherGenerator *ditherState );
 
 
 /**