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Removing most of the full-overlap assumptions from freq.[ch]

--- a/dnn/freq.c

+++ b/dnn/freq.c

@@ -51,7 +51,7 @@

 typedef struct {

   int init;

   kiss_fft_state *kfft;

-  float half_window[FRAME_SIZE];

+  float half_window[OVERLAP_SIZE];

   float dct_table[NB_BANDS*NB_BANDS];

 } CommonState;

@@ -127,9 +127,9 @@

 static void check_init() {

   int i;

   if (common.init) return;

-  common.kfft = opus_fft_alloc_twiddles(2*FRAME_SIZE, NULL, NULL, NULL, 0);

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

-    common.half_window[i] = sin(.5*M_PI*sin(.5*M_PI*(i+.5)/FRAME_SIZE) * sin(.5*M_PI*(i+.5)/FRAME_SIZE));

+  common.kfft = opus_fft_alloc_twiddles(WINDOW_SIZE, NULL, NULL, NULL, 0);

+  for (i=0;i<OVERLAP_SIZE;i++)

+    common.half_window[i] = sin(.5*M_PI*sin(.5*M_PI*(i+.5)/OVERLAP_SIZE) * sin(.5*M_PI*(i+.5)/OVERLAP_SIZE));

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

     int j;

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

@@ -209,10 +209,11 @@

    float rc[LPC_ORDER];

    float Xr[FREQ_SIZE];

    kiss_fft_cpx X_auto[FREQ_SIZE];

-   float x_auto[FRAME_SIZE];

+   float x_auto[WINDOW_SIZE];

    interp_band_gain(Xr, Ex);

+   Xr[FREQ_SIZE-1] = 0;

    RNN_CLEAR(X_auto, FREQ_SIZE);

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

+   for (i=0;i<FREQ_SIZE;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];

@@ -239,7 +240,7 @@

 void apply_window(float *x) {

   int i;

   check_init();

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

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

     x[i] *= common.half_window[i];

     x[WINDOW_SIZE - 1 - i] *= common.half_window[i];

   }

--- a/dnn/freq.h

+++ b/dnn/freq.h

@@ -30,8 +30,9 @@

 #define FRAME_SIZE_SHIFT 2

 #define FRAME_SIZE (40<<FRAME_SIZE_SHIFT)

-#define WINDOW_SIZE (2*FRAME_SIZE)

-#define FREQ_SIZE (FRAME_SIZE + 1)

+#define OVERLAP_SIZE (FRAME_SIZE)

+#define WINDOW_SIZE (FRAME_SIZE + OVERLAP_SIZE)

+#define FREQ_SIZE (WINDOW_SIZE/2 + 1)

 #define NB_BANDS 18

-- 

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