ref: ef8676867777ee1024a8c4a024cdd230c51d1d6a
dir: /silk/LPC_analysis_filter.c/
/***********************************************************************
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***********************************************************************/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "SigProc_FIX.h"
#include "celt_lpc.h"
/*******************************************/
/* LPC analysis filter */
/* NB! State is kept internally and the */
/* filter always starts with zero state */
/* first d output samples are set to zero */
/*******************************************/
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 */
int arch /* I Run-time architecture */
)
{
opus_int j;
#ifdef FIXED_POINT
opus_int16 mem[SILK_MAX_ORDER_LPC];
opus_int16 num[SILK_MAX_ORDER_LPC];
#else
int ix;
opus_int32 out32_Q12, out32;
const opus_int16 *in_ptr;
#endif
silk_assert( d >= 6 );
silk_assert( (d & 1) == 0 );
silk_assert( d <= len );
#ifdef FIXED_POINT
silk_assert( d <= SILK_MAX_ORDER_LPC );
for ( j = 0; j < d; j++ ) {
num[ j ] = -B[ j ];
}
for (j=0;j<d;j++) {
mem[ j ] = in[ d - j - 1 ];
}
celt_fir( in + d, num, out + d, len - d, d, mem, arch );
for ( j = 0; j < d; j++ ) {
out[ j ] = 0;
}
#else
(void)arch;
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 ) );
#endif
}