/* 16th order AR filter */
void SKP_Silk_LPC_synthesis_order16(const int16_t * in, /* I: excitation signal */
const int16_t * A_Q12, /* I: AR coefficients [16], between -8_Q0 and 8_Q0 */
const int32_t Gain_Q26, /* I: gain */
int32_t * S, /* I/O: state vector [16] */
int16_t * out, /* O: output signal */
const int32_t len /* I: signal length, must be multiple of 16 */
)
{
int k;
int32_t SA, SB, Atmp, A_align_Q12[8], out32_Q10, out32;
/* combine two A_Q12 values and ensure 32-bit alignment */
for (k = 0; k < 8; k++) {
A_align_Q12[k] =
(((int32_t) A_Q12[2 * k]) & 0x0000ffff) |
SKP_LSHIFT((int32_t) A_Q12[2 * k + 1], 16);
}
/* S[] values are in Q14 */
/* NOTE: the code below loads two int16 values in an int32, and multiplies each using the */
/* SMLAWB and SMLAWT instructions. On a big-endian CPU the two int16 variables would be */
/* loaded in reverse order and the code will give the wrong result. In that case swapping */
/* the SMLAWB and SMLAWT instructions should solve the problem. */
for (k = 0; k < len; k++) {
/* unrolled loop: prolog */
/* multiply-add two prediction coefficients per iteration */
SA = S[15];
Atmp = A_align_Q12[0];
SB = S[14];
S[14] = SA;
out32_Q10 = SKP_SMULWB(SA, Atmp);
out32_Q10 = SKP_SMLAWT_ovflw(out32_Q10, SB, Atmp);
SA = S[13];
S[13] = SB;
/* unrolled loop: main loop */
Atmp = A_align_Q12[1];
SB = S[12];
S[12] = SA;
out32_Q10 = SKP_SMLAWB_ovflw(out32_Q10, SA, Atmp);
out32_Q10 = SKP_SMLAWT_ovflw(out32_Q10, SB, Atmp);
SA = S[11];
S[11] = SB;
Atmp = A_align_Q12[2];
SB = S[10];
S[10] = SA;
out32_Q10 = SKP_SMLAWB_ovflw(out32_Q10, SA, Atmp);
out32_Q10 = SKP_SMLAWT_ovflw(out32_Q10, SB, Atmp);
SA = S[9];
S[9] = SB;
Atmp = A_align_Q12[3];
SB = S[8];
S[8] = SA;
out32_Q10 = SKP_SMLAWB_ovflw(out32_Q10, SA, Atmp);
out32_Q10 = SKP_SMLAWT_ovflw(out32_Q10, SB, Atmp);
SA = S[7];
S[7] = SB;
Atmp = A_align_Q12[4];
SB = S[6];
S[6] = SA;
out32_Q10 = SKP_SMLAWB_ovflw(out32_Q10, SA, Atmp);
out32_Q10 = SKP_SMLAWT_ovflw(out32_Q10, SB, Atmp);
SA = S[5];
S[5] = SB;
Atmp = A_align_Q12[5];
SB = S[4];
S[4] = SA;
out32_Q10 = SKP_SMLAWB_ovflw(out32_Q10, SA, Atmp);
out32_Q10 = SKP_SMLAWT_ovflw(out32_Q10, SB, Atmp);
SA = S[3];
S[3] = SB;
Atmp = A_align_Q12[6];
SB = S[2];
S[2] = SA;
out32_Q10 = SKP_SMLAWB_ovflw(out32_Q10, SA, Atmp);
out32_Q10 = SKP_SMLAWT_ovflw(out32_Q10, SB, Atmp);
SA = S[1];
S[1] = SB;
/* unrolled loop: epilog */
Atmp = A_align_Q12[7];
SB = S[0];
S[0] = SA;
out32_Q10 = SKP_SMLAWB_ovflw(out32_Q10, SA, Atmp);
out32_Q10 = SKP_SMLAWT_ovflw(out32_Q10, SB, Atmp);
/* 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] = (int16_t) SKP_SAT16(out32);
/* move result into delay line */
S[15] = SKP_LSHIFT_SAT32(out32_Q10, 4);
}
}
/* 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 );
}
}
