shithub: opus

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Constrain the pitch gain to prevent potential instabilities.

--- a/libcelt/bands.c

+++ b/libcelt/bands.c

@@ -211,7 +211,7 @@

    }

 }

-int compute_pitch_gain(const CELTMode *m, const celt_sig_t *X, const celt_sig_t *P, int norm_rate, int *gain_id, int _C)

+int compute_pitch_gain(const CELTMode *m, const celt_sig_t *X, const celt_sig_t *P, int norm_rate, int *gain_id, int _C, celt_word16_t *gain_prod)

 {

    int j, c;

    celt_word16_t g;

@@ -281,6 +281,16 @@

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

    }

 #endif

+   /* This prevents the pitch gain from being above 1.0 for too long by bounding the 

+      maximum error amplification factor to 2.0 */

+   g = ADD16(QCONST16(.5,14), MULT16_16_16(QCONST16(.05,14),*gain_id));

+   *gain_prod = MAX16(QCONST32(1., 13), MULT16_16_Q14(*gain_prod,g));

+   if (*gain_prod>QCONST32(2., 13))

+   {

+      *gain_id=9;

+      *gain_prod = QCONST32(2., 13);

+   }

+

    if (*gain_id < 0)

    {

       *gain_id = 0;

--- a/libcelt/bands.h

+++ b/libcelt/bands.h

@@ -71,7 +71,7 @@

  * @param gains Gain computed for each pitch band (returned)

  * @param bank Square root of the energy for each band

  */

-int compute_pitch_gain(const CELTMode *m, const celt_sig_t *X, const celt_sig_t *P, int norm_rate, int *gain_id, int _C);

+int compute_pitch_gain(const CELTMode *m, const celt_sig_t *X, const celt_sig_t *P, int norm_rate, int *gain_id, int _C, celt_word16_t *gain_prod);

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

--- a/libcelt/celt.c

+++ b/libcelt/celt.c

@@ -88,6 +88,7 @@

    int delayedIntra;

    celt_word16_t tonal_average;

    int fold_decision;

+   celt_word16_t gain_prod;

    int VBR_rate; /* Target number of 16th bits per frame */

    celt_word16_t * restrict preemph_memE; 

@@ -650,7 +651,7 @@

    {

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

-      has_pitch = compute_pitch_gain(st->mode, freq, pitch_freq, norm_rate, &gain_id, C);

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

    }

    if (has_pitch)