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27
28 #ifdef HAVE_CONFIG_H
29 #include "config.h"
30 #endif
31
32 /*
33 Elliptic/Cauer filters designed with 0.1 dB passband ripple,
34 80 dB minimum stopband attenuation, and
35 [0.95 : 0.15 : 0.35] normalized cut off frequencies.
36 */
37
38 #include "main.h"
39
40 /* Helper function, interpolates the filter taps */
silk_LP_interpolate_filter_taps(opus_int32 B_Q28[TRANSITION_NB],opus_int32 A_Q28[TRANSITION_NA],const opus_int ind,const opus_int32 fac_Q16)41 static OPUS_INLINE void silk_LP_interpolate_filter_taps(
42 opus_int32 B_Q28[ TRANSITION_NB ],
43 opus_int32 A_Q28[ TRANSITION_NA ],
44 const opus_int ind,
45 const opus_int32 fac_Q16
46 )
47 {
48 opus_int nb, na;
49
50 if( ind < TRANSITION_INT_NUM - 1 ) {
51 if( fac_Q16 > 0 ) {
52 if( fac_Q16 < 32768 ) { /* fac_Q16 is in range of a 16-bit int */
53 /* Piece-wise linear interpolation of B and A */
54 for( nb = 0; nb < TRANSITION_NB; nb++ ) {
55 B_Q28[ nb ] = silk_SMLAWB(
56 silk_Transition_LP_B_Q28[ ind ][ nb ],
57 silk_Transition_LP_B_Q28[ ind + 1 ][ nb ] -
58 silk_Transition_LP_B_Q28[ ind ][ nb ],
59 fac_Q16 );
60 }
61 for( na = 0; na < TRANSITION_NA; na++ ) {
62 A_Q28[ na ] = silk_SMLAWB(
63 silk_Transition_LP_A_Q28[ ind ][ na ],
64 silk_Transition_LP_A_Q28[ ind + 1 ][ na ] -
65 silk_Transition_LP_A_Q28[ ind ][ na ],
66 fac_Q16 );
67 }
68 } else { /* ( fac_Q16 - ( 1 << 16 ) ) is in range of a 16-bit int */
69 silk_assert( fac_Q16 - ( 1 << 16 ) == silk_SAT16( fac_Q16 - ( 1 << 16 ) ) );
70 /* Piece-wise linear interpolation of B and A */
71 for( nb = 0; nb < TRANSITION_NB; nb++ ) {
72 B_Q28[ nb ] = silk_SMLAWB(
73 silk_Transition_LP_B_Q28[ ind + 1 ][ nb ],
74 silk_Transition_LP_B_Q28[ ind + 1 ][ nb ] -
75 silk_Transition_LP_B_Q28[ ind ][ nb ],
76 fac_Q16 - ( (opus_int32)1 << 16 ) );
77 }
78 for( na = 0; na < TRANSITION_NA; na++ ) {
79 A_Q28[ na ] = silk_SMLAWB(
80 silk_Transition_LP_A_Q28[ ind + 1 ][ na ],
81 silk_Transition_LP_A_Q28[ ind + 1 ][ na ] -
82 silk_Transition_LP_A_Q28[ ind ][ na ],
83 fac_Q16 - ( (opus_int32)1 << 16 ) );
84 }
85 }
86 } else {
87 silk_memcpy( B_Q28, silk_Transition_LP_B_Q28[ ind ], TRANSITION_NB * sizeof( opus_int32 ) );
88 silk_memcpy( A_Q28, silk_Transition_LP_A_Q28[ ind ], TRANSITION_NA * sizeof( opus_int32 ) );
89 }
90 } else {
91 silk_memcpy( B_Q28, silk_Transition_LP_B_Q28[ TRANSITION_INT_NUM - 1 ], TRANSITION_NB * sizeof( opus_int32 ) );
92 silk_memcpy( A_Q28, silk_Transition_LP_A_Q28[ TRANSITION_INT_NUM - 1 ], TRANSITION_NA * sizeof( opus_int32 ) );
93 }
94 }
95
96 /* Low-pass filter with variable cutoff frequency based on */
97 /* piece-wise linear interpolation between elliptic filters */
98 /* Start by setting psEncC->mode <> 0; */
99 /* Deactivate by setting psEncC->mode = 0; */
silk_LP_variable_cutoff(silk_LP_state * psLP,opus_int16 * frame,const opus_int frame_length)100 void silk_LP_variable_cutoff(
101 silk_LP_state *psLP, /* I/O LP filter state */
102 opus_int16 *frame, /* I/O Low-pass filtered output signal */
103 const opus_int frame_length /* I Frame length */
104 )
105 {
106 opus_int32 B_Q28[ TRANSITION_NB ], A_Q28[ TRANSITION_NA ], fac_Q16 = 0;
107 opus_int ind = 0;
108
109 silk_assert( psLP->transition_frame_no >= 0 && psLP->transition_frame_no <= TRANSITION_FRAMES );
110
111 /* Run filter if needed */
112 if( psLP->mode != 0 ) {
113 /* Calculate index and interpolation factor for interpolation */
114 #if( TRANSITION_INT_STEPS == 64 )
115 fac_Q16 = silk_LSHIFT( TRANSITION_FRAMES - psLP->transition_frame_no, 16 - 6 );
116 #else
117 fac_Q16 = silk_DIV32_16( silk_LSHIFT( TRANSITION_FRAMES - psLP->transition_frame_no, 16 ), TRANSITION_FRAMES );
118 #endif
119 ind = silk_RSHIFT( fac_Q16, 16 );
120 fac_Q16 -= silk_LSHIFT( ind, 16 );
121
122 silk_assert( ind >= 0 );
123 silk_assert( ind < TRANSITION_INT_NUM );
124
125 /* Interpolate filter coefficients */
126 silk_LP_interpolate_filter_taps( B_Q28, A_Q28, ind, fac_Q16 );
127
128 /* Update transition frame number for next frame */
129 psLP->transition_frame_no = silk_LIMIT( psLP->transition_frame_no + psLP->mode, 0, TRANSITION_FRAMES );
130
131 /* ARMA low-pass filtering */
132 silk_assert( TRANSITION_NB == 3 && TRANSITION_NA == 2 );
133 silk_biquad_alt_stride1( frame, B_Q28, A_Q28, psLP->In_LP_State, frame, frame_length);
134 }
135 }
136