/* of int16s to make it fit in an int32 */
void silk_sum_sqr_shift(int32_t * energy, /* O Energy of x, after shifting to the right */
int * shift, /* O Number of bits right shift applied to energy */
const int16_t * x, /* I Input vector */
int len /* I Length of input vector */
)
{
int i, shft;
int32_t nrg_tmp, nrg;
nrg = 0;
shft = 0;
len--;
for (i = 0; i < len; i += 2) {
nrg = silk_SMLABB_ovflw(nrg, x[i], x[i]);
nrg = silk_SMLABB_ovflw(nrg, x[i + 1], x[i + 1]);
if (nrg < 0) {
/* Scale down */
nrg =
(int32_t) silk_RSHIFT_uint((uint32_t) nrg, 2);
shft = 2;
break;
}
}
for (; i < len; i += 2) {
nrg_tmp = silk_SMULBB(x[i], x[i]);
nrg_tmp = silk_SMLABB_ovflw(nrg_tmp, x[i + 1], x[i + 1]);
nrg =
(int32_t) silk_ADD_RSHIFT_uint(nrg,
(uint32_t) nrg_tmp,
shft);
if (nrg < 0) {
/* Scale down */
nrg =
(int32_t) silk_RSHIFT_uint((uint32_t) nrg, 2);
shft += 2;
}
}
if (i == len) {
/* One sample left to process */
nrg_tmp = silk_SMULBB(x[i], x[i]);
nrg = (int32_t) silk_ADD_RSHIFT_uint(nrg, nrg_tmp, shft);
}
/* Make sure to have at least one extra leading zero (two leading zeros in total) */
if (nrg & 0xC0000000) {
nrg = silk_RSHIFT_uint((uint32_t) nrg, 2);
shft += 2;
}
/* Output arguments */
*shift = shft;
*energy = nrg;
}
void silk_LPC_analysis_filter(
opus_int16 *out, /* O Output signal */
const opus_int16 *in, /* I Input signal */
const opus_int16 *B, /* I MA prediction coefficients, Q12 [order] */
const opus_int32 len, /* I Signal length */
const opus_int32 d /* I Filter order */
)
{
opus_int ix, j;
opus_int32 out32_Q12, out32;
const opus_int16 *in_ptr;
silk_assert( d >= 6 );
silk_assert( (d & 1) == 0 );
silk_assert( d <= len );
for( ix = d; ix < len; ix++ ) {
in_ptr = &in[ ix - 1 ];
out32_Q12 = silk_SMULBB( in_ptr[ 0 ], B[ 0 ] );
/* Allowing wrap around so that two wraps can cancel each other. The rare
cases where the result wraps around can only be triggered by invalid streams*/
out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -1 ], B[ 1 ] );
out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -2 ], B[ 2 ] );
out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -3 ], B[ 3 ] );
out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -4 ], B[ 4 ] );
out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -5 ], B[ 5 ] );
for( j = 6; j < d; j += 2 ) {
out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -j ], B[ j ] );
out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -j - 1 ], B[ j + 1 ] );
}
/* Subtract prediction */
out32_Q12 = silk_SUB32_ovflw( silk_LSHIFT( (opus_int32)in_ptr[ 1 ], 12 ), out32_Q12 );
/* Scale to Q0 */
out32 = silk_RSHIFT_ROUND( out32_Q12, 12 );
/* Saturate output */
out[ ix ] = (opus_int16)silk_SAT16( out32 );
}
/* Set first d output samples to zero */
silk_memset( out, 0, d * sizeof( opus_int16 ) );
}