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enabling denorm pitch only at low bit-rate

--- a/libcelt/bands.c

+++ b/libcelt/bands.c

@@ -216,7 +216,7 @@

    }

 }

-int compute_new_pitch(const CELTMode *m, const celt_sig_t *X, const celt_sig_t *P, int *gain_id)

+int compute_new_pitch(const CELTMode *m, const celt_sig_t *X, const celt_sig_t *P, int norm_rate, int *gain_id)

 {

    int j ;

    celt_word16_t g;

@@ -248,6 +248,10 @@

 #ifdef FIXED_POINT

    {

       celt_word32_t num, den;

+      celt_word16_t fact;

+      fact = MULT16_16(QCONST16(.04, 14), norm_rate);

+      if (fact < QCONST16(1., 14))

+         fact = QCONST16(1., 14);

       num = Sxy;

       den = EPSILON+Sxx+MULT16_32_Q15(QCONST16(.03,15),Syy);

       shift = celt_ilog2(Sxy)-16;

@@ -254,16 +258,21 @@

       if (shift < 0)

          shift = 0;

       g = DIV32(SHL32(SHR32(num,shift),14),SHR32(den,shift));

-      if (Sxy < SHR32(MULT16_16(celt_sqrt(EPSILON+Sxx),celt_sqrt(EPSILON+Syy)),1))

+      if (Sxy < MULT16_32_Q15(fact, MULT16_16(celt_sqrt(EPSILON+Sxx),celt_sqrt(EPSILON+Syy))))

          g = 0;

       /* This MUST round down */

       *gain_id = EXTRACT16(SHR32(MULT16_16(20,(g-QCONST16(.5,14))),14));

    }

 #else

-   g = Sxy/(.1+Sxx+.03*Syy);

-   if (Sxy < .5*celt_sqrt(.1+Sxx*Syy))

-      g = 0;

-   *gain_id = floor(20*(g-.5));

+   {

+      float fact = .04*norm_rate;

+      if (fact < 1)

+         fact = 1;

+      g = Sxy/(.1+Sxx+.03*Syy);

+      if (Sxy < .5*fact*celt_sqrt(1+Sxx*Syy))

+         g = 0;

+      *gain_id = floor(20*(g-.5));

+   }

 #endif

    if (*gain_id < 0)

    {

--- a/libcelt/bands.h

+++ b/libcelt/bands.h

@@ -64,7 +64,7 @@

  */

 void denormalise_bands(const CELTMode *m, const celt_norm_t * restrict X, celt_sig_t * restrict freq, const celt_ener_t *bands);

-int compute_new_pitch(const CELTMode *m, const celt_sig_t *X, const celt_sig_t *P, int *gain_id);

+int compute_new_pitch(const CELTMode *m, const celt_sig_t *X, const celt_sig_t *P, int norm_rate, int *gain_id);

 void apply_new_pitch(const CELTMode *m, celt_sig_t *X, const celt_sig_t *P, int gain_id, int pred);

--- a/libcelt/celt.c

+++ b/libcelt/celt.c

@@ -523,6 +523,7 @@

    int mdct_weight_shift = 0;

    int mdct_weight_pos=0;

    int gain_id=0;

+   int norm_rate;

    SAVE_STACK;

    if (check_encoder(st) != CELT_OK)

@@ -659,15 +660,13 @@

 #endif

    }

-   compute_band_energies(st->mode, freq, bandE);

-   for (i=0;i<st->mode->nbEBands*C;i++)

-      bandLogE[i] = amp2Log(bandE[i]);

-

+   norm_rate = (nbCompressedBytes-5)*8*(celt_uint32_t)st->mode->Fs/(C*N)>>10;

    /* Pitch analysis: we do it early to save on the peak stack space */

    /* Don't use pitch if there isn't enough data available yet, 

       or if we're using shortBlocks */

    has_pitch = st->pitch_enabled && st->pitch_permitted && (N <= 512) 

-            && (st->pitch_available >= MAX_PERIOD) && (!shortBlocks);

+            && (st->pitch_available >= MAX_PERIOD) && (!shortBlocks)

+            && norm_rate < 50;

    if (has_pitch)

    {

       find_spectral_pitch(st->mode, st->mode->fft, &st->mode->psy, in, st->out_mem, st->mode->window, NULL, 2*N-2*N4, MAX_PERIOD-(2*N-2*N4), &pitch_index);

@@ -682,8 +681,9 @@

    ALLOC(pitch_freq, C*N, celt_sig_t); /**< Interleaved signal MDCTs */

    if (has_pitch)

    {

+      

       compute_mdcts(st->mode, 0, st->out_mem+pitch_index*C, pitch_freq);

-      has_pitch = compute_new_pitch(st->mode, freq, pitch_freq, &gain_id);

+      has_pitch = compute_new_pitch(st->mode, freq, pitch_freq, norm_rate, &gain_id);

    }

    if (has_pitch)