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Compute LPC from features

--- a/dnn/common.h

+++ b/dnn/common.h

@@ -9,6 +9,8 @@

 #define RNN_INLINE inline

 #define OPUS_INLINE inline

+float lpc_from_cepstrum(float *lpc, const float *cepstrum);

+

 /** RNNoise wrapper for malloc(). To do your own dynamic allocation, all you need t

 o do is replace this function and rnnoise_free */

--- a/dnn/denoise.c

+++ b/dnn/denoise.c

@@ -222,6 +222,19 @@

   }

 }

+static void idct(float *out, const float *in) {

+  int i;

+  check_init();

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

+    int j;

+    float sum = 0;

+    for (j=0;j<NB_BANDS;j++) {

+      sum += in[j] * common.dct_table[i*NB_BANDS + j];

+    }

+    out[i] = sum*sqrt(2.*22)*(1.f/NB_BANDS);

+  }

+}

+

 #if 0

 static void idct(float *out, const float *in) {

   int i;

@@ -311,6 +324,41 @@

   int i;

   i = (int)floor(.5+x);

   return IMAX(-32767, IMIN(32767, i));

+}

+

+static float lpc_from_bands(float *lpc, const float *Ex)

+{

+   int i;

+   float e;

+   float ac[LPC_ORDER+1];

+   float rc[LPC_ORDER];

+   float Xr[FREQ_SIZE];

+   kiss_fft_cpx X_auto[FREQ_SIZE];

+   float x_auto[FRAME_SIZE];

+   interp_band_gain(Xr, Ex);

+   RNN_CLEAR(X_auto, FREQ_SIZE);

+   for (i=0;i<160;i++) X_auto[i].r = Xr[i];

+   inverse_transform(x_auto, X_auto);

+   for (i=0;i<LPC_ORDER+1;i++) ac[i] = x_auto[i];

+

+   /* -40 dB noise floor. */

+   ac[0] += ac[0]*1e-4 + 320/12/38.;

+   /* Lag windowing. */

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

+   e = _celt_lpc(lpc, rc, ac, LPC_ORDER);

+   return e;

+}

+

+float lpc_from_cepstrum(float *lpc, const float *cepstrum)

+{

+   int i;

+   float Ex[NB_BANDS];

+   float tmp[NB_BANDS];

+   RNN_COPY(tmp, cepstrum, NB_BANDS);

+   tmp[0] += 4;

+   idct(Ex, tmp);

+   for (i=0;i<NB_BANDS;i++) Ex[i] = pow(10.f, Ex[i]);

+   return lpc_from_bands(lpc, Ex);

 }

 static float frame_analysis(DenoiseState *st, signed char *iexc, short *pred, short *pcm, float *lpc, kiss_fft_cpx *X, float *Ex, const float *in) {

--- a/dnn/lpcnet.c

+++ b/dnn/lpcnet.c

@@ -142,7 +142,7 @@

     free(lpcnet);

 }

-void lpcnet_synthesize(LPCNetState *lpcnet, short *output, const float *features, const float *new_lpc, int N)

+void lpcnet_synthesize(LPCNetState *lpcnet, short *output, const float *features, int N)

 {

     int i;

     float condition[FEATURE_DENSE2_OUT_SIZE];

@@ -160,7 +160,7 @@

     run_frame_network(lpcnet, condition, gru_a_condition, features, pitch);

     memcpy(lpc, lpcnet->old_lpc[FEATURES_DELAY-1], LPC_ORDER*sizeof(lpc[0]));

     memmove(lpcnet->old_lpc[1], lpcnet->old_lpc[0], (FEATURES_DELAY-1)*LPC_ORDER*sizeof(lpc[0]));

-    memcpy(lpcnet->old_lpc[0], new_lpc, LPC_ORDER*sizeof(lpc[0]));

+    lpc_from_cepstrum(lpcnet->old_lpc[0], features);

     if (lpcnet->frame_count <= FEATURES_DELAY)

     {

         RNN_CLEAR(output, N);

@@ -208,14 +208,12 @@

     while (1) {

         float in_features[NB_TOTAL_FEATURES];

         float features[NB_FEATURES];

-        float lpc[LPC_ORDER];

         short pcm[FRAME_SIZE];

         fread(in_features, sizeof(features[0]), NB_TOTAL_FEATURES, fin);

         RNN_COPY(features, in_features, NB_FEATURES);

         RNN_CLEAR(&features[18], 18);

-        RNN_COPY(lpc, &in_features[NB_TOTAL_FEATURES-LPC_ORDER], LPC_ORDER);

         if (feof(fin)) break;

-        lpcnet_synthesize(net, pcm, features, lpc, FRAME_SIZE);

+        lpcnet_synthesize(net, pcm, features, FRAME_SIZE);

         fwrite(pcm, sizeof(pcm[0]), FRAME_SIZE, fout);

     }

     fclose(fin);

--- a/dnn/lpcnet.h

+++ b/dnn/lpcnet.h

@@ -33,6 +33,6 @@

 void lpcnet_destroy(LPCNetState *lpcnet);

-void lpcnet_synthesize(LPCNetState *lpcnet, short *output, const float *features, const float *new_lpc, int N);

+void lpcnet_synthesize(LPCNetState *lpcnet, short *output, const float *features, int N);

 #endif

-- 

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