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26***********************************************************************/
27
28#ifdef HAVE_CONFIG_H
29#include "config.h"
30#endif
31
32#include "SigProc_FIX.h"
33#include "celt_lpc.h"
34
35/*******************************************/
36/* LPC analysis filter                     */
37/* NB! State is kept internally and the    */
38/* filter always starts with zero state    */
39/* first d output samples are set to zero  */
40/*******************************************/
41
42void silk_LPC_analysis_filter(
43    opus_int16                  *out,               /* O    Output signal                                               */
44    const opus_int16            *in,                /* I    Input signal                                                */
45    const opus_int16            *B,                 /* I    MA prediction coefficients, Q12 [order]                     */
46    const opus_int32            len,                /* I    Signal length                                               */
47    const opus_int32            d                   /* I    Filter order                                                */
48)
49{
50    opus_int   j;
51#ifdef FIXED_POINT
52    opus_int16 mem[SILK_MAX_ORDER_LPC];
53    opus_int16 num[SILK_MAX_ORDER_LPC];
54#else
55    int ix;
56    opus_int32       out32_Q12, out32;
57    const opus_int16 *in_ptr;
58#endif
59
60    silk_assert( d >= 6 );
61    silk_assert( (d & 1) == 0 );
62    silk_assert( d <= len );
63
64#ifdef FIXED_POINT
65    silk_assert( d <= SILK_MAX_ORDER_LPC );
66    for ( j = 0; j < d; j++ ) {
67        num[ j ] = -B[ j ];
68    }
69    for (j=0;j<d;j++) {
70        mem[ j ] = in[ d - j - 1 ];
71    }
72    celt_fir( in + d, num, out + d, len - d, d, mem );
73    for ( j = 0; j < d; j++ ) {
74        out[ j ] = 0;
75    }
76#else
77    for( ix = d; ix < len; ix++ ) {
78        in_ptr = &in[ ix - 1 ];
79
80        out32_Q12 = silk_SMULBB( in_ptr[  0 ], B[ 0 ] );
81        /* Allowing wrap around so that two wraps can cancel each other. The rare
82           cases where the result wraps around can only be triggered by invalid streams*/
83        out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -1 ], B[ 1 ] );
84        out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -2 ], B[ 2 ] );
85        out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -3 ], B[ 3 ] );
86        out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -4 ], B[ 4 ] );
87        out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -5 ], B[ 5 ] );
88        for( j = 6; j < d; j += 2 ) {
89            out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -j     ], B[ j     ] );
90            out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -j - 1 ], B[ j + 1 ] );
91        }
92
93        /* Subtract prediction */
94        out32_Q12 = silk_SUB32_ovflw( silk_LSHIFT( (opus_int32)in_ptr[ 1 ], 12 ), out32_Q12 );
95
96        /* Scale to Q0 */
97        out32 = silk_RSHIFT_ROUND( out32_Q12, 12 );
98
99        /* Saturate output */
100        out[ ix ] = (opus_int16)silk_SAT16( out32 );
101    }
102
103    /* Set first d output samples to zero */
104    silk_memset( out, 0, d * sizeof( opus_int16 ) );
105#endif
106}
107