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--- a/dnn/dump_data.c

+++ b/dnn/dump_data.c

@@ -155,6 +155,7 @@

     static float xc[10][PITCH_MAX_PERIOD];

     static float ener[10][PITCH_MAX_PERIOD];

     static float frame_max_corr[PITCH_MAX_PERIOD];

+    /* Cross-correlation on half-frames. */

     for (sub=0;sub<2;sub++) {

       int off = sub*FRAME_SIZE/2;

       celt_pitch_xcorr(&st->exc_buf[PITCH_MAX_PERIOD+off], st->exc_buf+off, xcorr, FRAME_SIZE/2, PITCH_MAX_PERIOD);

@@ -170,6 +171,7 @@

 #endif

     }

     pcount++;

+    /* Running on groups of 4 frames. */

     if (pcount == 4) {

       int period;

       float best_a=0;

@@ -181,6 +183,8 @@

       int voiced;

       best_corr = -100;

       best_period = PITCH_MIN_PERIOD;

+      /* Search approximate pitch by considering the max correlation over all sub-frames

+         within a window corresponding to 25% of the pitch (4 semitones). */

       for (i=PITCH_MAX_PERIOD-PITCH_MIN_PERIOD*5/4;i>=0;i--) {

         int j;

         float corr;

@@ -235,6 +239,7 @@

       }

       frame_corr = sc/sw;

       voiced = frame_corr > .45;

+      /* Linear regression to figure out the pitch contour. */

       best_a = (sw*sxy - sx*sy)/(sw*sxx - sx*sx);

       if (voiced) {

         float mean_pitch = sy/sw;

@@ -246,6 +251,7 @@

       }

       //best_b = (sxx*sy - sx*sxy)/(sw*sxx - sx*sx);

       best_b = (sy - best_a*sx)/sw;

+      /* Quantizing the pitch as "main" pitch + slope. */

       float center_pitch = best_b+5.5*best_a;

       int main_pitch = (int)floor(.5 + 21.*log2(center_pitch/PITCH_MIN_PERIOD));

       main_pitch = IMAX(0, IMIN(63, main_pitch));

-- 

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