shithub: opus

Info  •  Files  •  Log  •  Branches

Prevent overshoots from CELT PLC with prediction

Constrains the energy prediction to something safe.

--- a/celt/celt_decoder.c

+++ b/celt/celt_decoder.c

@@ -1183,6 +1183,36 @@

    /* Decode the global flags (first symbols in the stream) */

    intra_ener = tell+3<=total_bits ? ec_dec_bit_logp(dec, 3) : 0;

+   /* If recovering from packet loss, make sure we make the energy prediction safe to reduce the

+      risk of getting loud artifacts. */

+   if (!intra_ener && st->loss_duration != 0) {

+      c=0; do

+      {

+         opus_val16 safety = 0;

+         int missing = IMIN(10, st->loss_duration>>LM);

+         if (LM==0) safety = QCONST16(1.5f,DB_SHIFT);

+         else if (LM==1) safety = QCONST16(.5f,DB_SHIFT);

+         for (i=start;i<end;i++)

+         {

+            if (oldBandE[c*nbEBands+i] < MAX16(oldLogE[c*nbEBands+i], oldLogE2[c*nbEBands+i])) {

+               /* If energy is going down already, continue the trend. */

+               opus_val32 slope;

+               opus_val32 E0, E1, E2;

+               E0 = oldBandE[c*nbEBands+i];

+               E1 = oldLogE[c*nbEBands+i];

+               E2 = oldLogE2[c*nbEBands+i];

+               slope = MAX32(E1 - E0, HALF32(E2 - E0));

+               E0 -= MAX32(0, (1+missing)*slope);

+               oldBandE[c*nbEBands+i] = MAX32(-QCONST16(20.f,DB_SHIFT), E0);

+            } else {

+               /* Otherwise take the min of the last frames. */

+               oldBandE[c*nbEBands+i] = MIN16(MIN16(oldBandE[c*nbEBands+i], oldLogE[c*nbEBands+i]), oldLogE2[c*nbEBands+i]);

+            }

+            /* Shorter frames have more natural fluctuations -- play it safe. */

+            oldBandE[c*nbEBands+i] -= safety;

+         }

+      } while (++c<2);

+   }

    /* Get band energies */

    unquant_coarse_energy(mode, start, end, oldBandE,

          intra_ener, dec, C, LM);

-- 

⑨