ref: 310af750eb5726b4143a43208f2bc03677c6f5db
dir: /silk/SKP_Silk_LPC_synthesis_order16.c/
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/* *
* SKP_Silk_LPC_synthesis_order16.c *
* Coefficients are in Q12 *
* *
* 16th order AR filter *
* */
#include "SKP_Silk_SigProc_FIX.h"
/* 16th order AR filter */
void SKP_Silk_LPC_synthesis_order16(const SKP_int16 *in, /* I: excitation signal */
const SKP_int16 *A_Q12, /* I: AR coefficients [16], between -8_Q0 and 8_Q0 */
const SKP_int32 Gain_Q26, /* I: gain */
SKP_int32 *S, /* I/O: state vector [16] */
SKP_int16 *out, /* O: output signal */
const SKP_int32 len /* I: signal length, must be multiple of 16 */
)
{
SKP_int k;
SKP_int32 SA, SB, out32_Q10, out32;
for( k = 0; k < len; k++ ) {
/* unrolled loop: prolog */
/* multiply-add two prediction coefficients per iteration */
SA = S[ 15 ];
SB = S[ 14 ];
S[ 14 ] = SA;
out32_Q10 = SKP_SMULWB( SA, A_Q12[ 0 ] );
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SB, A_Q12[ 1 ] );
SA = S[ 13 ];
S[ 13 ] = SB;
/* unrolled loop: main loop */
SB = S[ 12 ];
S[ 12 ] = SA;
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SA, A_Q12[ 2 ] );
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SB, A_Q12[ 3 ] );
SA = S[ 11 ];
S[ 11 ] = SB;
SB = S[ 10 ];
S[ 10 ] = SA;
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SA, A_Q12[ 4 ] );
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SB, A_Q12[ 5 ] );
SA = S[ 9 ];
S[ 9 ] = SB;
SB = S[ 8 ];
S[ 8 ] = SA;
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SA, A_Q12[ 6 ] );
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SB, A_Q12[ 7 ] );
SA = S[ 7 ];
S[ 7 ] = SB;
SB = S[ 6 ];
S[ 6 ] = SA;
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SA, A_Q12[ 8 ] );
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SB, A_Q12[ 9 ] );
SA = S[ 5 ];
S[ 5 ] = SB;
SB = S[ 4 ];
S[ 4 ] = SA;
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SA, A_Q12[ 10 ] );
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SB, A_Q12[ 11 ] );
SA = S[ 3 ];
S[ 3 ] = SB;
SB = S[ 2 ];
S[ 2 ] = SA;
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SA, A_Q12[ 12 ] );
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SB, A_Q12[ 13 ] );
SA = S[ 1 ];
S[ 1 ] = SB;
/* unrolled loop: epilog */
SB = S[ 0 ];
S[ 0 ] = SA;
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SA, A_Q12[ 14 ] );
out32_Q10 = SKP_SMLAWB_ovflw( out32_Q10, SB, A_Q12[ 15 ] );
/* unrolled loop: end */
/* apply gain to excitation signal and add to prediction */
out32_Q10 = SKP_ADD_SAT32( out32_Q10, SKP_SMULWB( Gain_Q26, in[ k ] ) );
/* scale to Q0 */
out32 = SKP_RSHIFT_ROUND( out32_Q10, 10 );
/* saturate output */
out[ k ] = ( SKP_int16 )SKP_SAT16( out32 );
/* move result into delay line */
S[ 15 ] = SKP_LSHIFT_SAT32( out32_Q10, 4 );
}
}