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27
28 /* *
29 * silk_biquad_alt.c *
30 * *
31 * Second order ARMA filter *
32 * Can handle slowly varying filter coefficients *
33 * */
34
35 #ifdef HAVE_CONFIG_H
36 #include "config.h"
37 #endif
38
39 #include "SigProc_FIX.h"
40
41 /* Second order ARMA filter, alternative implementation */
silk_biquad_alt_stride1(const opus_int16 * in,const opus_int32 * B_Q28,const opus_int32 * A_Q28,opus_int32 * S,opus_int16 * out,const opus_int32 len)42 void silk_biquad_alt_stride1(
43 const opus_int16 *in, /* I input signal */
44 const opus_int32 *B_Q28, /* I MA coefficients [3] */
45 const opus_int32 *A_Q28, /* I AR coefficients [2] */
46 opus_int32 *S, /* I/O State vector [2] */
47 opus_int16 *out, /* O output signal */
48 const opus_int32 len /* I signal length (must be even) */
49 )
50 {
51 /* DIRECT FORM II TRANSPOSED (uses 2 element state vector) */
52 opus_int k;
53 opus_int32 inval, A0_U_Q28, A0_L_Q28, A1_U_Q28, A1_L_Q28, out32_Q14;
54
55 /* Negate A_Q28 values and split in two parts */
56 A0_L_Q28 = ( -A_Q28[ 0 ] ) & 0x00003FFF; /* lower part */
57 A0_U_Q28 = silk_RSHIFT( -A_Q28[ 0 ], 14 ); /* upper part */
58 A1_L_Q28 = ( -A_Q28[ 1 ] ) & 0x00003FFF; /* lower part */
59 A1_U_Q28 = silk_RSHIFT( -A_Q28[ 1 ], 14 ); /* upper part */
60
61 for( k = 0; k < len; k++ ) {
62 /* S[ 0 ], S[ 1 ]: Q12 */
63 inval = in[ k ];
64 out32_Q14 = silk_LSHIFT( silk_SMLAWB( S[ 0 ], B_Q28[ 0 ], inval ), 2 );
65
66 S[ 0 ] = S[1] + silk_RSHIFT_ROUND( silk_SMULWB( out32_Q14, A0_L_Q28 ), 14 );
67 S[ 0 ] = silk_SMLAWB( S[ 0 ], out32_Q14, A0_U_Q28 );
68 S[ 0 ] = silk_SMLAWB( S[ 0 ], B_Q28[ 1 ], inval);
69
70 S[ 1 ] = silk_RSHIFT_ROUND( silk_SMULWB( out32_Q14, A1_L_Q28 ), 14 );
71 S[ 1 ] = silk_SMLAWB( S[ 1 ], out32_Q14, A1_U_Q28 );
72 S[ 1 ] = silk_SMLAWB( S[ 1 ], B_Q28[ 2 ], inval );
73
74 /* Scale back to Q0 and saturate */
75 out[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT( out32_Q14 + (1<<14) - 1, 14 ) );
76 }
77 }
78
silk_biquad_alt_stride2_c(const opus_int16 * in,const opus_int32 * B_Q28,const opus_int32 * A_Q28,opus_int32 * S,opus_int16 * out,const opus_int32 len)79 void silk_biquad_alt_stride2_c(
80 const opus_int16 *in, /* I input signal */
81 const opus_int32 *B_Q28, /* I MA coefficients [3] */
82 const opus_int32 *A_Q28, /* I AR coefficients [2] */
83 opus_int32 *S, /* I/O State vector [4] */
84 opus_int16 *out, /* O output signal */
85 const opus_int32 len /* I signal length (must be even) */
86 )
87 {
88 /* DIRECT FORM II TRANSPOSED (uses 2 element state vector) */
89 opus_int k;
90 opus_int32 A0_U_Q28, A0_L_Q28, A1_U_Q28, A1_L_Q28, out32_Q14[ 2 ];
91
92 /* Negate A_Q28 values and split in two parts */
93 A0_L_Q28 = ( -A_Q28[ 0 ] ) & 0x00003FFF; /* lower part */
94 A0_U_Q28 = silk_RSHIFT( -A_Q28[ 0 ], 14 ); /* upper part */
95 A1_L_Q28 = ( -A_Q28[ 1 ] ) & 0x00003FFF; /* lower part */
96 A1_U_Q28 = silk_RSHIFT( -A_Q28[ 1 ], 14 ); /* upper part */
97
98 for( k = 0; k < len; k++ ) {
99 /* S[ 0 ], S[ 1 ], S[ 2 ], S[ 3 ]: Q12 */
100 out32_Q14[ 0 ] = silk_LSHIFT( silk_SMLAWB( S[ 0 ], B_Q28[ 0 ], in[ 2 * k + 0 ] ), 2 );
101 out32_Q14[ 1 ] = silk_LSHIFT( silk_SMLAWB( S[ 2 ], B_Q28[ 0 ], in[ 2 * k + 1 ] ), 2 );
102
103 S[ 0 ] = S[ 1 ] + silk_RSHIFT_ROUND( silk_SMULWB( out32_Q14[ 0 ], A0_L_Q28 ), 14 );
104 S[ 2 ] = S[ 3 ] + silk_RSHIFT_ROUND( silk_SMULWB( out32_Q14[ 1 ], A0_L_Q28 ), 14 );
105 S[ 0 ] = silk_SMLAWB( S[ 0 ], out32_Q14[ 0 ], A0_U_Q28 );
106 S[ 2 ] = silk_SMLAWB( S[ 2 ], out32_Q14[ 1 ], A0_U_Q28 );
107 S[ 0 ] = silk_SMLAWB( S[ 0 ], B_Q28[ 1 ], in[ 2 * k + 0 ] );
108 S[ 2 ] = silk_SMLAWB( S[ 2 ], B_Q28[ 1 ], in[ 2 * k + 1 ] );
109
110 S[ 1 ] = silk_RSHIFT_ROUND( silk_SMULWB( out32_Q14[ 0 ], A1_L_Q28 ), 14 );
111 S[ 3 ] = silk_RSHIFT_ROUND( silk_SMULWB( out32_Q14[ 1 ], A1_L_Q28 ), 14 );
112 S[ 1 ] = silk_SMLAWB( S[ 1 ], out32_Q14[ 0 ], A1_U_Q28 );
113 S[ 3 ] = silk_SMLAWB( S[ 3 ], out32_Q14[ 1 ], A1_U_Q28 );
114 S[ 1 ] = silk_SMLAWB( S[ 1 ], B_Q28[ 2 ], in[ 2 * k + 0 ] );
115 S[ 3 ] = silk_SMLAWB( S[ 3 ], B_Q28[ 2 ], in[ 2 * k + 1 ] );
116
117 /* Scale back to Q0 and saturate */
118 out[ 2 * k + 0 ] = (opus_int16)silk_SAT16( silk_RSHIFT( out32_Q14[ 0 ] + (1<<14) - 1, 14 ) );
119 out[ 2 * k + 1 ] = (opus_int16)silk_SAT16( silk_RSHIFT( out32_Q14[ 1 ] + (1<<14) - 1, 14 ) );
120 }
121 }
122