Fixed small sinc() calculation bug that caused AA filter attenuation be around -10dB instead of <-50dB.

1 files changed, 31 insertions, 4 deletions

diff --git a/source/SoundTouch/AAFilter.cpp b/source/SoundTouch/AAFilter.cpp
index 191b97b..1efffe1 100644
--- a/source/SoundTouch/AAFilter.cpp
+++ b/source/SoundTouch/AAFilter.cpp
@@ -52,6 +52,30 @@ using namespace soundtouch;
 #define PI        3.141592655357989

 #define TWOPI    (2 * PI)

 

+// define this to save AA filter coefficients to a file

+// #define _DEBUG_SAVE_AAFILTER_COEFFICIENTS   1

+

+#ifdef _DEBUG_SAVE_AAFILTER_COEFFICIENTS

+    #include <stdio.h>

+

+    static void _DEBUG_SAVE_AAFIR_COEFFS(SAMPLETYPE *coeffs, int len)

+    {

+        FILE *fptr = fopen("aa_filter_coeffs.txt", "wt");

+        if (fptr == NULL) return;

+

+        for (int i = 0; i < len; i ++)

+        {

+            double temp = coeffs[i];

+            fprintf(fptr, "%lf\n", temp);

+        }

+        fclose(fptr);

+    }

+

+#else

+    #define _DEBUG_SAVE_AAFIR_COEFFS(x, y) ()

+#endif

+

+

 /*****************************************************************************

  *

  * Implementation of the class 'AAFilter'

@@ -112,8 +136,7 @@ void AAFilter::calculateCoeffs()
     work = new double[length];

     coeffs = new SAMPLETYPE[length];

 

-    fc2 = 2.0 * cutoffFreq; 

-    wc = PI * fc2;

+    wc = 2.0 * PI * cutoffFreq;

     tempCoeff = TWOPI / (double)length;

 

     sum = 0;

@@ -124,7 +147,7 @@ void AAFilter::calculateCoeffs()
         temp = cntTemp * wc;

         if (temp != 0) 

         {

-            h = fc2 * sin(temp) / temp;                     // sinc function

+            h = sin(temp) / temp;                     // sinc function

         } 

         else 

         {

@@ -153,17 +176,21 @@ void AAFilter::calculateCoeffs()
 

     for (i = 0; i < length; i ++) 

     {

-        // scale & round to nearest integer

         temp = work[i] * scaleCoeff;

+//#if SOUNDTOUCH_INTEGER_SAMPLES

+        // scale & round to nearest integer

         temp += (temp >= 0) ? 0.5 : -0.5;

         // ensure no overfloods

         assert(temp >= -32768 && temp <= 32767);

+//#endif

         coeffs[i] = (SAMPLETYPE)temp;

     }

 

     // Set coefficients. Use divide factor 14 => divide result by 2^14 = 16384

     pFIR->setCoefficients(coeffs, length, 14);

 

+    _DEBUG_SAVE_AAFIR_COEFFS(coeffs, length);

+

     delete[] work;

     delete[] coeffs;

 }