CopySamples gives more than binary choice of dither algorithm...

... And so a separate function CopySamplesNoDither is not needed

src/Mix.cpp

@@ -691,7 +691,7 @@ size_t Mixer::Process(size_t maxToProcess)
             mBuffer[0].ptr() + (c * SAMPLE_SIZE(mFormat)),
             mFormat,
             maxOut,
-            mHighQuality,
+            mHighQuality ? gHighQualityDither : gLowQualityDither,
             mNumChannels,
             mNumChannels);
       }
@@ -703,7 +703,7 @@ size_t Mixer::Process(size_t maxToProcess)
             mBuffer[c].ptr(),
             mFormat,
             maxOut,
-            mHighQuality);
+            mHighQuality ? gHighQualityDither : gLowQualityDither);
       }
    }
    // MB: this doesn't take warping into account, replaced with code based on mSamplePos

src/SampleFormat.cpp

@@ -43,11 +43,10 @@
 #include <string.h>
 
 #include "Prefs.h"
-#include "Dither.h"
 #include "Internat.h"
 
-static DitherType gLowQualityDither = DitherType::none;
-static DitherType gHighQualityDither = DitherType::none;
+DitherType gLowQualityDither = DitherType::none;
+DitherType gHighQualityDither = DitherType::shaped;
 static Dither gDitherAlgorithm;
 
 void InitDitherers()
@@ -104,29 +103,17 @@ void  SamplesToFloats(constSamplePtr src, sampleFormat srcFormat,
 {
    CopySamples( src, srcFormat,
       reinterpret_cast<samplePtr>(dst), floatSample, len,
-      true, // doesn't matter, no dither happens when destination is float
+      DitherType::none,
       srcStride, dstStride);
 }
 
 void CopySamples(constSamplePtr src, sampleFormat srcFormat,
-                 samplePtr dst, sampleFormat dstFormat,
-                 unsigned int len,
-                 bool highQuality, /* = true */
-                 unsigned int srcStride /* = 1 */,
-                 unsigned int dstStride /* = 1 */)
+   samplePtr dst, sampleFormat dstFormat, size_t len,
+   DitherType ditherType, /* = gHighQualityDither */
+   unsigned int srcStride /* = 1 */,
+   unsigned int dstStride /* = 1 */)
 {
    gDitherAlgorithm.Apply(
-      highQuality ? gHighQualityDither : gLowQualityDither,
-      src, srcFormat, dst, dstFormat, len, srcStride, dstStride);
-}
-
-void CopySamplesNoDither(samplePtr src, sampleFormat srcFormat,
-                 samplePtr dst, sampleFormat dstFormat,
-                 unsigned int len,
-                 unsigned int srcStride /* = 1 */,
-                 unsigned int dstStride /* = 1 */)
-{
-   gDitherAlgorithm.Apply(
-      DitherType::none,
+      ditherType,
       src, srcFormat, dst, dstFormat, len, srcStride, dstStride);
 }

src/SampleFormat.h

@@ -2,7 +2,7 @@
 
   Audacity: A Digital Audio Editor
 
-  SampleFormat.h
+  @file SampleFormat.h
 
   Dominic Mazzoni
 
@@ -17,11 +17,15 @@
 #include <wx/defs.h>
 
 #include "audacity/Types.h"
+#include "Dither.h"
 
 //
 // Definitions / Meta-Information
 //
 
+//! These global variables are assigned at application startup or after change of preferences.
+extern AUDACITY_DLL_API DitherType gLowQualityDither, gHighQualityDither;
+
 #if 0
 // Moved to audacity/types.h
 typedef enum {
@@ -138,18 +142,16 @@ void SamplesToFloats(constSamplePtr src, sampleFormat srcFormat,
     float *dst, size_t len, size_t srcStride = 1, size_t dstStride = 1);
 
 AUDACITY_DLL_API
-void      CopySamples(constSamplePtr src, sampleFormat srcFormat,
-                      samplePtr dst, sampleFormat dstFormat,
-                      unsigned int len, bool highQuality=true,
-                      unsigned int srcStride=1,
-                      unsigned int dstStride=1);
-
-AUDACITY_DLL_API
-void      CopySamplesNoDither(samplePtr src, sampleFormat srcFormat,
-                      samplePtr dst, sampleFormat dstFormat,
-                      unsigned int len,
-                      unsigned int srcStride=1,
-                      unsigned int dstStride=1);
+//! Copy samples from any format to any other format; apply dithering only if narrowing the format
+/*!
+ @copydetails SamplesToFloats()
+ @param dstFormat format of destination samples, determines sizeof each one
+ @param ditherType choice of dithering algorithm to use if narrowing the format
+ */
+void CopySamples(constSamplePtr src, sampleFormat srcFormat,
+   samplePtr dst, sampleFormat dstFormat, size_t len,
+   DitherType ditherType = gHighQualityDither, //!< default is loaded from a global variable
+   unsigned int srcStride=1, unsigned int dstStride=1);
 
 AUDACITY_DLL_API
 void      ClearSamples(samplePtr buffer, sampleFormat format,

src/WaveClip.cpp

@@ -1248,7 +1248,7 @@ bool WaveClip::Append(constSamplePtr buffer, sampleFormat format,
                   mAppendBuffer.ptr() + mAppendBufferLen * SAMPLE_SIZE(seqFormat),
                   seqFormat,
                   toCopy,
-                  true, // high quality
+                  gHighQualityDither,
                   stride);
 
       mAppendBufferLen += toCopy;

src/export/ExportPCM.cpp

@@ -643,12 +643,13 @@ ProgressResult ExportPCM::Export(AudacityProject *project,
                   CopySamples(
                      mixed + (c * SAMPLE_SIZE(format)), format,
                      dither.data() + (c * SAMPLE_SIZE(int24Sample)), int24Sample,
-                     numSamples, true, info.channels, info.channels
+                     numSamples, gHighQualityDither, info.channels, info.channels
                   );
-                  CopySamplesNoDither(
+                  // Copy back without dither
+                  CopySamples(
                      dither.data() + (c * SAMPLE_SIZE(int24Sample)), int24Sample,
                      mixed + (c * SAMPLE_SIZE(format)), format,
-                     numSamples, info.channels, info.channels);
+                     numSamples, DitherType::none, info.channels, info.channels);
                }
             }
 

src/import/ImportAUP.cpp

@@ -1640,7 +1640,7 @@ bool AUPImportFileHandle::AddSamples(const FilePath &blockFilename,
                   bufptr,
                   format,
                   framesRead,
-                  true /* high quality by default */,
+                  gHighQualityDither /* high quality by default */,
                   channels /* source stride */);
    }