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Prevent overshoots from CELT PLC with prediction

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Constrains the energy prediction to something safe.
This commit is contained in:
Jean-Marc Valin 2023-12-22 20:14:10 -05:00
parent bd2e9a34fb
commit 6ad03ae03e
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GPG Key ID: 5E5DD9A36F9189C8
1 changed files with 30 additions and 0 deletions
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celt/celt_decoder.c
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@ -1183,6 +1183,36 @@ int celt_decode_with_ec_dred(CELTDecoder * OPUS_RESTRICT st, const unsigned char
/* 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);