/* For input in Q24 domain */
opus_int32 silk_LPC_inverse_pred_gain_Q24( /* O Returns inverse prediction gain in energy domain, Q30 */
const opus_int32 *A_Q24, /* I Prediction coefficients [order] */
const opus_int order /* I Prediction order */
)
{
opus_int k;
opus_int32 Atmp_QA[ SILK_MAX_ORDER_LPC ];
/* Increase Q domain of the AR coefficients */
for( k = 0; k < order; k++ ) {
Atmp_QA[ k ] = silk_RSHIFT32( A_Q24[ k ], 24 - QA );
}
return LPC_inverse_pred_gain_QA( Atmp_QA, order );
}
/* For input in Q24 domain */
int32_t silk_LPC_inverse_pred_gain_Q24( /* O Returns inverse prediction gain in energy domain, Q30 */
const int32_t * A_Q24, /* I Prediction coefficients [order] */
const int order /* I Prediction order */
)
{
int k;
int32_t Atmp_QA[2][SILK_MAX_ORDER_LPC];
int32_t *Anew_QA;
memzero(Atmp_QA, (2 * SILK_MAX_ORDER_LPC) * sizeof(int32_t));
Anew_QA = Atmp_QA[order & 1];
/* Increase Q domain of the AR coefficients */
for (k = 0; k < order; k++) {
Anew_QA[k] = silk_RSHIFT32(A_Q24[k], 24 - QA);
}
return LPC_inverse_pred_gain_QA(Atmp_QA, order);
}
/* For input in Q12 domain */
opus_int32 silk_LPC_inverse_pred_gain( /* O Returns inverse prediction gain in energy domain, Q30 */
const opus_int16 *A_Q12, /* I Prediction coefficients, Q12 [order] */
const opus_int order /* I Prediction order */
)
{
opus_int k;
opus_int32 Atmp_QA[ SILK_MAX_ORDER_LPC ];
opus_int32 DC_resp = 0;
/* Increase Q domain of the AR coefficients */
for( k = 0; k < order; k++ ) {
DC_resp += (opus_int32)A_Q12[ k ];
Atmp_QA[ k ] = silk_LSHIFT32( (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 0;
}
return LPC_inverse_pred_gain_QA( Atmp_QA, order );
}
