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Add LPC analysis

--- a/dnn/celt_lpc.h

+++ b/dnn/celt_lpc.h

@@ -35,7 +35,7 @@

 #include "x86/celt_lpc_sse.h"

 #endif

-#define LPC_ORDER 24

+#define LPC_ORDER 16

 void _celt_lpc(opus_val16 *_lpc, const opus_val32 *ac, int p);

--- a/dnn/denoise.c

+++ b/dnn/denoise.c

@@ -37,7 +37,10 @@

 #include "rnnoise.h"

 #include "pitch.h"

 #include "arch.h"

+#include "celt_lpc.h"

+#define PREEMPHASIS (0.85f)

+

 #define FRAME_SIZE_SHIFT 2

 #define FRAME_SIZE (40<<FRAME_SIZE_SHIFT)

 #define WINDOW_SIZE (2*FRAME_SIZE)

@@ -305,10 +308,23 @@

 static void frame_analysis(DenoiseState *st, kiss_fft_cpx *X, float *Ex, const float *in) {

   int i;

   float x[WINDOW_SIZE];

+  float ac[LPC_ORDER+1];

+  float lpc[LPC_ORDER];

   RNN_COPY(x, st->analysis_mem, FRAME_SIZE);

   for (i=0;i<FRAME_SIZE;i++) x[FRAME_SIZE + i] = in[i];

   RNN_COPY(st->analysis_mem, in, FRAME_SIZE);

   apply_window(x);

+  {

+    _celt_autocorr(x, ac, NULL, 0, LPC_ORDER, WINDOW_SIZE);

+    /* -40 dB noise floor. */

+    ac[0] -= ac[0]*1e-4;

+    /* Lag windowing. */

+    for (i=1;i<LPC_ORDER+1;i++) ac[i] *= (1 - 6e-5*i*i);

+    _celt_lpc(lpc, ac, LPC_ORDER);

+    printf("1 ");

+    for(i=0;i<LPC_ORDER;i++) printf("%f ", lpc[i]);

+    printf("\n");

+  }

   forward_transform(X, x);

 #if TRAINING

   for (i=lowpass;i<FREQ_SIZE;i++)

@@ -429,6 +445,16 @@

   }

 }

+static void preemphasis(float *y, float *mem, const float *x, float coef, int N) {

+  int i;

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

+    float yi;

+    yi = x[i] + *mem;

+    *mem = -coef*x[i];

+    y[i] = yi;

+  }

+}

+

 void pitch_filter(kiss_fft_cpx *X, const kiss_fft_cpx *P, const float *Ex, const float *Ep,

                   const float *Exp, const float *g) {

   int i;

@@ -521,6 +547,7 @@

   static const float a_hp[2] = {-1.99599, 0.99600};

   static const float b_hp[2] = {-2, 1};

   float mem_hp_x[2]={0};

+  float mem_preemph=0;

   float x[FRAME_SIZE];

   FILE *f1;

   DenoiseState *st;

@@ -546,10 +573,11 @@

     for (i=0;i<FRAME_SIZE;i++) x[i] = tmp[i];

     for (i=0;i<FRAME_SIZE;i++) E += tmp[i]*(float)tmp[i];

     biquad(x, mem_hp_x, x, b_hp, a_hp, FRAME_SIZE);

+    preemphasis(x, &mem_preemph, x, PREEMPHASIS, FRAME_SIZE);

     compute_frame_features(st, X, P, Ex, Ep, Exp, features, x);

     pitch_filter(X, P, Ex, Ep, Exp, g);

-#if 1

+#if 0

     fwrite(features, sizeof(float), NB_FEATURES, stdout);

     fwrite(g, sizeof(float), NB_BANDS, stdout);

     fwrite(Ln, sizeof(float), NB_BANDS, stdout);

-- 

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