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27
28 #ifdef HAVE_CONFIG_H
29 #include "config.h"
30 #endif
31
32 #include "SigProc_FIX.h"
33
34 /* Apply sine window to signal vector. */
35 /* Window types: */
36 /* 1 -> sine window from 0 to pi/2 */
37 /* 2 -> sine window from pi/2 to pi */
38 /* Every other sample is linearly interpolated, for speed. */
39 /* Window length must be between 16 and 120 (incl) and a multiple of 4. */
40
41 /* Matlab code for table:
42 for k=16:9*4:16+2*9*4, fprintf(' %7.d,', -round(65536*pi ./ (k:4:k+8*4))); fprintf('\n'); end
43 */
44 static const opus_int16 freq_table_Q16[ 27 ] = {
45 12111, 9804, 8235, 7100, 6239, 5565, 5022, 4575, 4202,
46 3885, 3612, 3375, 3167, 2984, 2820, 2674, 2542, 2422,
47 2313, 2214, 2123, 2038, 1961, 1889, 1822, 1760, 1702,
48 };
49
silk_apply_sine_window(opus_int16 px_win[],const opus_int16 px[],const opus_int win_type,const opus_int length)50 void silk_apply_sine_window(
51 opus_int16 px_win[], /* O Pointer to windowed signal */
52 const opus_int16 px[], /* I Pointer to input signal */
53 const opus_int win_type, /* I Selects a window type */
54 const opus_int length /* I Window length, multiple of 4 */
55 )
56 {
57 opus_int k, f_Q16, c_Q16;
58 opus_int32 S0_Q16, S1_Q16;
59
60 silk_assert( win_type == 1 || win_type == 2 );
61
62 /* Length must be in a range from 16 to 120 and a multiple of 4 */
63 silk_assert( length >= 16 && length <= 120 );
64 silk_assert( ( length & 3 ) == 0 );
65
66 /* Frequency */
67 k = ( length >> 2 ) - 4;
68 silk_assert( k >= 0 && k <= 26 );
69 f_Q16 = (opus_int)freq_table_Q16[ k ];
70
71 /* Factor used for cosine approximation */
72 c_Q16 = silk_SMULWB( (opus_int32)f_Q16, -f_Q16 );
73 silk_assert( c_Q16 >= -32768 );
74
75 /* initialize state */
76 if( win_type == 1 ) {
77 /* start from 0 */
78 S0_Q16 = 0;
79 /* approximation of sin(f) */
80 S1_Q16 = f_Q16 + silk_RSHIFT( length, 3 );
81 } else {
82 /* start from 1 */
83 S0_Q16 = ( (opus_int32)1 << 16 );
84 /* approximation of cos(f) */
85 S1_Q16 = ( (opus_int32)1 << 16 ) + silk_RSHIFT( c_Q16, 1 ) + silk_RSHIFT( length, 4 );
86 }
87
88 /* Uses the recursive equation: sin(n*f) = 2 * cos(f) * sin((n-1)*f) - sin((n-2)*f) */
89 /* 4 samples at a time */
90 for( k = 0; k < length; k += 4 ) {
91 px_win[ k ] = (opus_int16)silk_SMULWB( silk_RSHIFT( S0_Q16 + S1_Q16, 1 ), px[ k ] );
92 px_win[ k + 1 ] = (opus_int16)silk_SMULWB( S1_Q16, px[ k + 1] );
93 S0_Q16 = silk_SMULWB( S1_Q16, c_Q16 ) + silk_LSHIFT( S1_Q16, 1 ) - S0_Q16 + 1;
94 S0_Q16 = silk_min( S0_Q16, ( (opus_int32)1 << 16 ) );
95
96 px_win[ k + 2 ] = (opus_int16)silk_SMULWB( silk_RSHIFT( S0_Q16 + S1_Q16, 1 ), px[ k + 2] );
97 px_win[ k + 3 ] = (opus_int16)silk_SMULWB( S0_Q16, px[ k + 3 ] );
98 S1_Q16 = silk_SMULWB( S0_Q16, c_Q16 ) + silk_LSHIFT( S0_Q16, 1 ) - S1_Q16;
99 S1_Q16 = silk_min( S1_Q16, ( (opus_int32)1 << 16 ) );
100 }
101 }
102