shithub: opus

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Fixes a numerical accuracy issue in the pitch search

The energy "sliding window" was using double accumulation with
float multiplications. This forces the multiplications to be
double as well.

--- a/silk/float/energy_FLP.c

+++ b/silk/float/energy_FLP.c

@@ -41,18 +41,18 @@

     double   result;

     /* 4x unrolled loop */

-    result = 0.0f;

+    result = 0.0;

     dataSize4 = dataSize & 0xFFFC;

     for( i = 0; i < dataSize4; i += 4 ) {

-        result += data[ i + 0 ] * data[ i + 0 ] +

-                  data[ i + 1 ] * data[ i + 1 ] +

-                  data[ i + 2 ] * data[ i + 2 ] +

-                  data[ i + 3 ] * data[ i + 3 ];

+        result += data[ i + 0 ] * (double)data[ i + 0 ] +

+                  data[ i + 1 ] * (double)data[ i + 1 ] +

+                  data[ i + 2 ] * (double)data[ i + 2 ] +

+                  data[ i + 3 ] * (double)data[ i + 3 ];

     }

     /* add any remaining products */

     for( ; i < dataSize; i++ ) {

-        result += data[ i ] * data[ i ];

+        result += data[ i ] * (double)data[ i ];

     }

     silk_assert( result >= 0.0 );

--- a/silk/float/pitch_analysis_core_FLP.c

+++ b/silk/float/pitch_analysis_core_FLP.c

@@ -610,11 +610,11 @@

         lag_diff = ( matrix_ptr( Lag_range_ptr, k, 1, 2 ) -  matrix_ptr( Lag_range_ptr, k, 0, 2 ) + 1 );

         for( i = 1; i < lag_diff; i++ ) {

             /* remove part outside new window */

-            energy -= basis_ptr[sf_length - i] * basis_ptr[sf_length - i];

+            energy -= basis_ptr[sf_length - i] * (double)basis_ptr[sf_length - i];

             silk_assert( energy >= 0.0 );

             /* add part that comes into window */

-            energy += basis_ptr[ -i ] * basis_ptr[ -i ];

+            energy += basis_ptr[ -i ] * (double)basis_ptr[ -i ];

             silk_assert( energy >= 0.0 );

             silk_assert( lag_counter < SCRATCH_SIZE );

             scratch_mem[lag_counter] = (silk_float)energy;