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Band-limiting the voicing parameter

--- a/dnn/lpcnet_enc.c

+++ b/dnn/lpcnet_enc.c

@@ -74,6 +74,19 @@

   lpcn_compute_band_energy(Ex, X);

 }

+static void biquad(float *y, float mem[2], const float *x, const float *b, const float *a, int N) {

+  int i;

+  for (i=0;i<N;i++) {

+    float xi, yi;

+    xi = x[i];

+    yi = x[i] + mem[0];

+    mem[0] = mem[1] + (b[0]*(double)xi - a[0]*(double)yi);

+    mem[1] = (b[1]*(double)xi - a[1]*(double)yi);

+    y[i] = yi;

+  }

+}

+

+

 void compute_frame_features(LPCNetEncState *st, const float *in) {

   float aligned_in[FRAME_SIZE];

   int i;

@@ -86,6 +99,9 @@

   float ener0;

   int sub;

   float ener;

+  /* [b,a]=ellip(2, 2, 20, 1200/8000); */

+  static const float lp_b[2] = {-0.84946f, 1.f};

+  static const float lp_a[2] = {-1.54220f, 0.70781f};

   OPUS_COPY(aligned_in, &st->analysis_mem[OVERLAP_SIZE-TRAINING_OFFSET], TRAINING_OFFSET);

   frame_analysis(st, X, Ex, in);

   logMax = -2;

@@ -102,6 +118,7 @@

   lpc_from_cepstrum(st->lpc, st->features);

   for (i=0;i<LPC_ORDER;i++) st->features[NB_BANDS+2+i] = st->lpc[i];

   OPUS_MOVE(st->exc_buf, &st->exc_buf[FRAME_SIZE], PITCH_MAX_PERIOD);

+  OPUS_MOVE(st->lp_buf, &st->lp_buf[FRAME_SIZE], PITCH_MAX_PERIOD);

   OPUS_COPY(&aligned_in[TRAINING_OFFSET], in, FRAME_SIZE-TRAINING_OFFSET);

   for (i=0;i<FRAME_SIZE;i++) {

     int j;

@@ -110,10 +127,12 @@

       sum += st->lpc[j]*st->pitch_mem[j];

     OPUS_MOVE(st->pitch_mem+1, st->pitch_mem, LPC_ORDER-1);

     st->pitch_mem[0] = aligned_in[i];

+    st->lp_buf[PITCH_MAX_PERIOD+i] = sum;

     st->exc_buf[PITCH_MAX_PERIOD+i] = sum + .7f*st->pitch_filt;

     st->pitch_filt = sum;

     /*printf("%f\n", st->exc_buf[PITCH_MAX_PERIOD+i]);*/

   }

+  biquad(&st->lp_buf[PITCH_MAX_PERIOD], st->lp_mem, &st->lp_buf[PITCH_MAX_PERIOD], lp_b, lp_a, FRAME_SIZE);

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

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

     int off = sub*FRAME_SIZE/2;

@@ -206,6 +225,17 @@

     best_i = pitch_prev[sub][best_i];

   }

   frame_corr /= 2;

+  if (0) {

+    float xy, xx, yy;

+    int pitch = (best[2]+best[3])/2;

+    xx = celt_inner_prod_c(&st->lp_buf[PITCH_MAX_PERIOD], &st->lp_buf[PITCH_MAX_PERIOD], FRAME_SIZE);

+    yy = celt_inner_prod_c(&st->lp_buf[PITCH_MAX_PERIOD-pitch], &st->lp_buf[PITCH_MAX_PERIOD-pitch], FRAME_SIZE);

+    xy = celt_inner_prod_c(&st->lp_buf[PITCH_MAX_PERIOD], &st->lp_buf[PITCH_MAX_PERIOD-pitch], FRAME_SIZE);

+    //printf("%f %f\n", frame_corr, xy/sqrt(1e-15+xx*yy));

+    frame_corr = xy/sqrt(1+xx*yy);

+    //frame_corr = MAX32(0, xy/sqrt(1+xx*yy));

+    frame_corr = log(1.f+exp(5.f*frame_corr))/log(1+exp(5.f));

+  }

   st->features[NB_BANDS] = .01f*(IMAX(66, IMIN(510, best[2]+best[3]))-200);

   st->features[NB_BANDS + 1] = frame_corr-.5f;

   if (ffeat) {

--- a/dnn/lpcnet_private.h

+++ b/dnn/lpcnet_private.h

@@ -49,6 +49,8 @@

   float xc[2][PITCH_MAX_PERIOD+1];

   float frame_weight[2];

   float exc_buf[PITCH_BUF_SIZE];

+  float lp_buf[PITCH_BUF_SIZE];

+  float lp_mem[4];

   float pitch_max_path[2][PITCH_MAX_PERIOD];

   float pitch_max_path_all;

   int best_i;

-- 

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