–Added interpolation to WASAPI's sample rate converter

1 files changed, 116 insertions, 31 deletions

diff --git a/RtAudio.cpp b/RtAudio.cpp
index 882fa0e..cdb98d7 100644
--- a/RtAudio.cpp
+++ b/RtAudio.cpp
@@ -1,4 +1,4 @@
-/************************************************************************/

+/************************************************************************/

 /*! \class RtAudio

     \brief Realtime audio i/o C++ classes.

 

@@ -3859,8 +3859,7 @@ private:
 // In order to satisfy WASAPI's buffer requirements, we need a means of converting sample rate

 // between HW and the user. The convertBufferWasapi function is used to perform this conversion

 // between HwIn->UserIn and UserOut->HwOut during the stream callback loop.

-// This sample rate converter favors speed over quality, and works best with conversions between

-// one rate and its multiple.

+// This sample rate converter works best with conversions between one rate and its multiple.

 void convertBufferWasapi( char* outBuffer,

                           const char* inBuffer,

                           const unsigned int& channelCount,

@@ -3872,40 +3871,126 @@ void convertBufferWasapi( char* outBuffer,
 {

   // calculate the new outSampleCount and relative sampleStep

   float sampleRatio = ( float ) outSampleRate / inSampleRate;

+  float sampleRatioInv = ( float ) 1 / sampleRatio;

   float sampleStep = 1.0f / sampleRatio;

   float inSampleFraction = 0.0f;

 

   outSampleCount = ( unsigned int ) roundf( inSampleCount * sampleRatio );

 

-  // frame-by-frame, copy each relative input sample into it's corresponding output sample

-  for ( unsigned int outSample = 0; outSample < outSampleCount; outSample++ )

+  // if inSampleRate is a multiple of outSampleRate (or vice versa) there's no need to interpolate

+  if (floor(sampleRatio) == sampleRatio || floor(sampleRatioInv) == sampleRatioInv)

   {

-    unsigned int inSample = ( unsigned int ) inSampleFraction;

-

-    switch ( format )

-    {

-      case RTAUDIO_SINT8:

-        memcpy( &( ( char* ) outBuffer )[ outSample * channelCount ], &( ( char* ) inBuffer )[ inSample * channelCount ], channelCount * sizeof( char ) );

-        break;

-      case RTAUDIO_SINT16:

-        memcpy( &( ( short* ) outBuffer )[ outSample * channelCount ], &( ( short* ) inBuffer )[ inSample * channelCount ], channelCount * sizeof( short ) );

-        break;

-      case RTAUDIO_SINT24:

-        memcpy( &( ( S24* ) outBuffer )[ outSample * channelCount ], &( ( S24* ) inBuffer )[ inSample * channelCount ], channelCount * sizeof( S24 ) );

-        break;

-      case RTAUDIO_SINT32:

-        memcpy( &( ( int* ) outBuffer )[ outSample * channelCount ], &( ( int* ) inBuffer )[ inSample * channelCount ], channelCount * sizeof( int ) );

-        break;

-      case RTAUDIO_FLOAT32:

-        memcpy( &( ( float* ) outBuffer )[ outSample * channelCount ], &( ( float* ) inBuffer )[ inSample * channelCount ], channelCount * sizeof( float ) );

-        break;

-      case RTAUDIO_FLOAT64:

-        memcpy( &( ( double* ) outBuffer )[ outSample * channelCount ], &( ( double* ) inBuffer )[ inSample * channelCount ], channelCount * sizeof( double ) );

-        break;

-    }

-

-    // jump to next in sample

-    inSampleFraction += sampleStep;

+	  // frame-by-frame, copy each relative input sample into it's corresponding output sample

+	  for (unsigned int outSample = 0; outSample < outSampleCount; outSample++)

+	  {

+		  unsigned int inSample = (unsigned int)inSampleFraction;

+

+		  switch (format)

+		  {

+		  case RTAUDIO_SINT8:

+			  memcpy(&((char*)outBuffer)[outSample * channelCount], &((char*)inBuffer)[inSample * channelCount], channelCount * sizeof(char));

+			  break;

+		  case RTAUDIO_SINT16:

+			  memcpy(&((short*)outBuffer)[outSample * channelCount], &((short*)inBuffer)[inSample * channelCount], channelCount * sizeof(short));

+			  break;

+		  case RTAUDIO_SINT24:

+			  memcpy(&((S24*)outBuffer)[outSample * channelCount], &((S24*)inBuffer)[inSample * channelCount], channelCount * sizeof(S24));

+			  break;

+		  case RTAUDIO_SINT32:

+			  memcpy(&((int*)outBuffer)[outSample * channelCount], &((int*)inBuffer)[inSample * channelCount], channelCount * sizeof(int));

+			  break;

+		  case RTAUDIO_FLOAT32:

+			  memcpy(&((float*)outBuffer)[outSample * channelCount], &((float*)inBuffer)[inSample * channelCount], channelCount * sizeof(float));

+			  break;

+		  case RTAUDIO_FLOAT64:

+			  memcpy(&((double*)outBuffer)[outSample * channelCount], &((double*)inBuffer)[inSample * channelCount], channelCount * sizeof(double));

+			  break;

+		  }

+

+		  // jump to next in sample

+		  inSampleFraction += sampleStep;

+	  }

+  }

+  else // else interpolate

+  {

+	  // frame-by-frame, copy each relative input sample into it's corresponding output sample

+	  for (unsigned int outSample = 0; outSample < outSampleCount; outSample++)

+	  {

+		  unsigned int inSample = (unsigned int)inSampleFraction;

+

+		  switch (format)

+		  {

+		  case RTAUDIO_SINT8:

+		  {

+			  for (unsigned int channel = 0; channel < channelCount; channel++)

+			  {

+				  char fromSample = ((char*)inBuffer)[(inSample * channelCount) + channel];

+				  char toSample = ((char*)inBuffer)[((inSample + 1) * channelCount) + channel];

+				  float sampleDiff = (toSample - fromSample) * (inSampleFraction - floor(inSampleFraction));

+				  ((char*)outBuffer)[(outSample * channelCount) + channel] = fromSample + (char)sampleDiff;

+			  }

+			  break;

+		  }

+		  case RTAUDIO_SINT16:

+		  {

+			  for (unsigned int channel = 0; channel < channelCount; channel++)

+			  {

+				  short fromSample = ((short*)inBuffer)[(inSample * channelCount) + channel];

+				  short toSample = ((short*)inBuffer)[((inSample + 1) * channelCount) + channel];

+				  float sampleDiff = (toSample - fromSample) * (inSampleFraction - floor(inSampleFraction));

+				  ((short*)outBuffer)[(outSample * channelCount) + channel] = fromSample + (short)sampleDiff;

+			  }

+			  break;

+		  }

+		  case RTAUDIO_SINT24:

+		  {

+			  for (unsigned int channel = 0; channel < channelCount; channel++)

+			  {

+				  int fromSample = ((S24*)inBuffer)[(inSample * channelCount) + channel].asInt();

+				  int toSample = ((S24*)inBuffer)[((inSample + 1) * channelCount) + channel].asInt();

+				  float sampleDiff = (toSample - fromSample) * (inSampleFraction - floor(inSampleFraction));

+				  ((S24*)outBuffer)[(outSample * channelCount) + channel] = fromSample + (int)sampleDiff;

+			  }

+			  break;

+		  }

+		  case RTAUDIO_SINT32:

+		  {

+			  for (unsigned int channel = 0; channel < channelCount; channel++)

+			  {

+				  int fromSample = ((int*)inBuffer)[(inSample * channelCount) + channel];

+				  int toSample = ((int*)inBuffer)[((inSample + 1) * channelCount) + channel];

+				  float sampleDiff = (toSample - fromSample) * (inSampleFraction - floor(inSampleFraction));

+				  ((int*)outBuffer)[(outSample * channelCount) + channel] = fromSample + (int)sampleDiff;

+			  }

+			  break;

+		  }

+		  case RTAUDIO_FLOAT32:

+		  {

+			  for (unsigned int channel = 0; channel < channelCount; channel++)

+			  {

+				  float fromSample = ((float*)inBuffer)[(inSample * channelCount) + channel];

+				  float toSample = ((float*)inBuffer)[((inSample + 1) * channelCount) + channel];

+				  float sampleDiff = (toSample - fromSample) * (inSampleFraction - floor(inSampleFraction));

+				  ((float*)outBuffer)[(outSample * channelCount) + channel] = fromSample + sampleDiff;

+			  }

+			  break;

+		  }

+		  case RTAUDIO_FLOAT64:

+		  {

+			  for (unsigned int channel = 0; channel < channelCount; channel++)

+			  {

+				  double fromSample = ((double*)inBuffer)[(inSample * channelCount) + channel];

+				  double toSample = ((double*)inBuffer)[((inSample + 1) * channelCount) + channel];

+				  double sampleDiff = (toSample - fromSample) * (inSampleFraction - floor(inSampleFraction));

+				  ((double*)outBuffer)[(outSample * channelCount) + channel] = fromSample + sampleDiff;

+			  }

+			  break;

+		  }

+		  }

+

+		  // jump to next in sample

+		  inSampleFraction += sampleStep;

+	  }

   }

 }