Corrected rescaling issue in the implementation of the MFCCs

Source/ComplexMathFunctions/arm_cmplx_mag_q15.c

@@ -131,7 +131,7 @@ void arm_cmplx_mag_q15(
       acc0 = __SMUAD(in, in);
   
       /* store result in 2.14 format in destination buffer. */
-      arm_sqrt_q31(acc0  >> 1 , &res);
+      arm_sqrt_q31((uint32_t)acc0  >> 1 , &res);
       *pDst++ = res >> 16;
   
   
@@ -170,22 +170,22 @@ void arm_cmplx_mag_q15(
     in = read_q15x2_ia (&pSrc);
     acc0 = __SMUAD(in, in);
     /* store result in 2.14 format in destination buffer. */
-    arm_sqrt_q31(acc0  >> 1 , &res);
+    arm_sqrt_q31((uint32_t)acc0  >> 1 , &res);
     *pDst++ = res >> 16;
 
     in = read_q15x2_ia (&pSrc);
     acc0 = __SMUAD(in, in);
-    arm_sqrt_q31(acc0  >> 1 , &res);
+    arm_sqrt_q31((uint32_t)acc0  >> 1 , &res);
     *pDst++ = res >> 16;
 
     in = read_q15x2_ia (&pSrc);
     acc0 = __SMUAD(in, in);
-    arm_sqrt_q31(acc0  >> 1 , &res);
+    arm_sqrt_q31((uint32_t)acc0  >> 1 , &res);
     *pDst++ = res >> 16;
 
     in = read_q15x2_ia (&pSrc);
     acc0 = __SMUAD(in, in);
-    arm_sqrt_q31(acc0  >> 1 , &res);
+    arm_sqrt_q31((uint32_t)acc0  >> 1 , &res);
     *pDst++ = res >> 16;
 #else
     real = *pSrc++;
@@ -194,28 +194,28 @@ void arm_cmplx_mag_q15(
     acc1 = ((q31_t) imag * imag);
 
     /* store result in 2.14 format in destination buffer. */
-    arm_sqrt_q31((acc0 + acc1) >> 1 , &res);
+    arm_sqrt_q31(((uint32_t)acc0 + (uint32_t)acc1) >> 1 , &res);
     *pDst++ = res >> 16;
 
     real = *pSrc++;
     imag = *pSrc++;
     acc0 = ((q31_t) real * real);
     acc1 = ((q31_t) imag * imag);
-    arm_sqrt_q31((acc0 + acc1) >> 1 , &res);
+    arm_sqrt_q31(((uint32_t)acc0 + (uint32_t)acc1) >> 1 , &res);
     *pDst++ = res >> 16;
 
     real = *pSrc++;
     imag = *pSrc++;
     acc0 = ((q31_t) real * real);
     acc1 = ((q31_t) imag * imag);
-    arm_sqrt_q31((acc0 + acc1) >> 1 , &res);
+    arm_sqrt_q31(((uint32_t)acc0 + (uint32_t)acc1) >> 1 , &res);
     *pDst++ = res >> 16;
 
     real = *pSrc++;
     imag = *pSrc++;
     acc0 = ((q31_t) real * real);
     acc1 = ((q31_t) imag * imag);
-    arm_sqrt_q31((acc0 + acc1) >> 1 , &res);
+    arm_sqrt_q31(((uint32_t)acc0 + (uint32_t)acc1) >> 1 , &res);
     *pDst++ = res >> 16;
 #endif /* #if defined (ARM_MATH_DSP) */
 
@@ -240,9 +240,8 @@ void arm_cmplx_mag_q15(
 #if defined (ARM_MATH_DSP)
     in = read_q15x2_ia (&pSrc);
     acc0 = __SMUAD(in, in);
-
     /* store result in 2.14 format in destination buffer. */
-    arm_sqrt_q31(acc0  >> 1 , &res);
+    arm_sqrt_q31((uint32_t)acc0  >> 1 , &res);
     *pDst++ = res >> 16;
 #else
     real = *pSrc++;
@@ -251,7 +250,7 @@ void arm_cmplx_mag_q15(
     acc1 = ((q31_t) imag * imag);
 
     /* store result in 2.14 format in destination buffer. */
-    arm_sqrt_q31((acc0 + acc1) >> 1 , &res);
+    arm_sqrt_q31(((uint32_t)acc0 + (uint32_t)acc1) >> 1 , &res);
     *pDst++ = res >> 16;
  
 #endif

Source/TransformFunctions/arm_mfcc_f16.c

@@ -94,7 +94,10 @@ void arm_mfcc_f16(
   /* Normalize */
   arm_absmax_f16(pSrc,S->fftLen,&maxValue,&index);
 
-  arm_scale_f16(pSrc,1.0f16/(_Float16)maxValue,pSrc,S->fftLen);
+  if ((_Float16)maxValue != 0.0f16)
+  {
+     arm_scale_f16(pSrc,1.0f16/(_Float16)maxValue,pSrc,S->fftLen);
+  }
 
   /* Multiply by window */
   arm_mult_f16(pSrc,S->windowCoefs,pSrc,S->fftLen);
@@ -125,6 +128,10 @@ void arm_mfcc_f16(
   pTmp[1]=0.0f;
 #endif
   arm_cmplx_mag_f16(pTmp,pSrc,S->fftLen);
+  if ((_Float16)maxValue != 0.0f16)
+  {
+     arm_scale_f16(pSrc,maxValue,pSrc,S->fftLen);
+  }
 
   /* Apply MEL filters */
   for(i=0; i<S->nbMelFilters; i++)

Source/TransformFunctions/arm_mfcc_f32.c

@@ -84,7 +84,10 @@ void arm_mfcc_f32(
   /* Normalize */
   arm_absmax_f32(pSrc,S->fftLen,&maxValue,&index);
 
-  arm_scale_f32(pSrc,1.0f/maxValue,pSrc,S->fftLen);
+  if (maxValue != 0.0f)
+  {
+     arm_scale_f32(pSrc,1.0f/maxValue,pSrc,S->fftLen);
+  }
 
   /* Multiply by window */
   arm_mult_f32(pSrc,S->windowCoefs,pSrc,S->fftLen);
@@ -115,6 +118,10 @@ void arm_mfcc_f32(
   pTmp[1]=0.0f;
 #endif
   arm_cmplx_mag_f32(pTmp,pSrc,S->fftLen);
+  if (maxValue != 0.0f)
+  {
+     arm_scale_f32(pSrc,maxValue,pSrc,S->fftLen);
+  }
 
   /* Apply MEL filters */
   for(i=0; i<S->nbMelFilters; i++)

Source/TransformFunctions/arm_mfcc_q15.c

@@ -72,7 +72,6 @@
                    point computations may saturate.
 
  */
-
 arm_status arm_mfcc_q15(
   const arm_mfcc_instance_q15 * S,
   q15_t *pSrc,
@@ -163,7 +162,11 @@ arm_status arm_mfcc_q15(
 
     }
 
-
+    if (m != 0)
+    {
+      arm_scale_q31(pTmp,m<<16,0,pTmp,S->nbMelFilters);
+    }
+   
     // q34.29 - fftShift - satShift
     /* Compute the log */
     arm_vlog_q31(pTmp,pTmp,S->nbMelFilters);

Source/TransformFunctions/arm_mfcc_q31.c

@@ -73,7 +73,6 @@
 
  */
 
-
 arm_status arm_mfcc_q31(
   const arm_mfcc_instance_q31 * S,
   q31_t *pSrc,
@@ -155,6 +154,7 @@ arm_status arm_mfcc_q31(
         S->filterLengths[i],
         &result);
 
+
       coefsPos += S->filterLengths[i];
 
       // q16.48 - fftShift
@@ -165,7 +165,11 @@ arm_status arm_mfcc_q31(
 
     }
 
-
+    if (m != 0)
+    {
+      arm_scale_q31(pTmp,m,0,pTmp,S->nbMelFilters);
+    }
+   
     // q16.29 - fftShift - satShift
     /* Compute the log */
     arm_vlog_q31(pTmp,pTmp,S->nbMelFilters);