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Cheap early detection of unstable filters

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We check the DC gain before doing the full RC calculations
This commit is contained in:
Jean-Marc Valin 2011-10-10 01:57:22 -04:00
parent 3346d88390
commit 53ea87fb96
1 changed files with 6 additions and 1 deletions
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7
silk/LPC_inv_pred_gain.c
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@ -117,14 +117,19 @@ opus_int silk_LPC_inverse_pred_gain( /* O: Returns 1 if unstable,
opus_int k;
opus_int32 Atmp_QA[ 2 ][ SILK_MAX_ORDER_LPC ];
opus_int32 *Anew_QA;
opus_int32 DC_resp=0;
Anew_QA = Atmp_QA[ order & 1 ];
/* Increase Q domain of the AR coefficients */
for( k = 0; k < order; k++ ) {
DC_resp += (opus_int32)A_Q12[ k ];
Anew_QA[ k ] = silk_LSHIFT( (opus_int32)A_Q12[ k ], QA - 12 );
}
/* If the DC is unstable, we don't even need to do the full calculations */
if ( DC_resp >= 4096 ) {
return 1;
}
return LPC_inverse_pred_gain_QA( invGain_Q30, Atmp_QA, order );
}