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Prevent overflows in PLC celt_iir()

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This commit is contained in:
Jean-Marc Valin 2016-07-22 11:05:19 -04:00
parent a0bd7d3b84
commit 3c60bae2d7
1 changed files with 17 additions and 1 deletions
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18
celt/celt_decoder.c
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@ -632,7 +632,23 @@ static void celt_decode_lost(CELTDecoder * OPUS_RESTRICT st, int N, int LM)
SIG_SHIFT);
S1 += SHR32(MULT16_16(tmp, tmp), 9);
}
#ifdef FIXED_POINT
/* For fixed-point, apply bandwidth expansion until we can guarantee that
no overflow can happen in the IIR filter. This means:
attenuation*32768*sum(abs(filter)) < 2^31 */
while (1) {
opus_val16 tmp=Q15ONE;
opus_val32 sum=QCONST16(1., SIG_SHIFT);
for (i=0;i<LPC_ORDER;i++)
sum += ABS16(lpc[c*LPC_ORDER+i]);
if (MULT16_32_Q15(attenuation, sum) < 65535) break;
for (i=0;i<LPC_ORDER;i++)
{
tmp = MULT16_16_Q15(QCONST16(.99f,15), tmp);
lpc[c*LPC_ORDER+i] = MULT16_16_Q15(lpc[c*LPC_ORDER+i], tmp);
}
}
#endif
{
opus_val16 lpc_mem[LPC_ORDER];
/* Copy the last decoded samples (prior to the overlap region) to