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27 :
28 : #ifdef HAVE_CONFIG_H
29 : #include "config.h"
30 : #endif
31 :
32 : /* NLSF stabilizer: */
33 : /* */
34 : /* - Moves NLSFs further apart if they are too close */
35 : /* - Moves NLSFs away from borders if they are too close */
36 : /* - High effort to achieve a modification with minimum */
37 : /* Euclidean distance to input vector */
38 : /* - Output are sorted NLSF coefficients */
39 : /* */
40 :
41 : #include "SigProc_FIX.h"
42 :
43 : /* Constant Definitions */
44 : #define MAX_LOOPS 20
45 :
46 : /* NLSF stabilizer, for a single input data vector */
47 0 : void silk_NLSF_stabilize(
48 : opus_int16 *NLSF_Q15, /* I/O Unstable/stabilized normalized LSF vector in Q15 [L] */
49 : const opus_int16 *NDeltaMin_Q15, /* I Min distance vector, NDeltaMin_Q15[L] must be >= 1 [L+1] */
50 : const opus_int L /* I Number of NLSF parameters in the input vector */
51 : )
52 : {
53 0 : opus_int i, I=0, k, loops;
54 : opus_int16 center_freq_Q15;
55 : opus_int32 diff_Q15, min_diff_Q15, min_center_Q15, max_center_Q15;
56 :
57 : /* This is necessary to ensure an output within range of a opus_int16 */
58 0 : silk_assert( NDeltaMin_Q15[L] >= 1 );
59 :
60 0 : for( loops = 0; loops < MAX_LOOPS; loops++ ) {
61 : /**************************/
62 : /* Find smallest distance */
63 : /**************************/
64 : /* First element */
65 0 : min_diff_Q15 = NLSF_Q15[0] - NDeltaMin_Q15[0];
66 0 : I = 0;
67 : /* Middle elements */
68 0 : for( i = 1; i <= L-1; i++ ) {
69 0 : diff_Q15 = NLSF_Q15[i] - ( NLSF_Q15[i-1] + NDeltaMin_Q15[i] );
70 0 : if( diff_Q15 < min_diff_Q15 ) {
71 0 : min_diff_Q15 = diff_Q15;
72 0 : I = i;
73 : }
74 : }
75 : /* Last element */
76 0 : diff_Q15 = ( 1 << 15 ) - ( NLSF_Q15[L-1] + NDeltaMin_Q15[L] );
77 0 : if( diff_Q15 < min_diff_Q15 ) {
78 0 : min_diff_Q15 = diff_Q15;
79 0 : I = L;
80 : }
81 :
82 : /***************************************************/
83 : /* Now check if the smallest distance non-negative */
84 : /***************************************************/
85 0 : if( min_diff_Q15 >= 0 ) {
86 0 : return;
87 : }
88 :
89 0 : if( I == 0 ) {
90 : /* Move away from lower limit */
91 0 : NLSF_Q15[0] = NDeltaMin_Q15[0];
92 :
93 0 : } else if( I == L) {
94 : /* Move away from higher limit */
95 0 : NLSF_Q15[L-1] = ( 1 << 15 ) - NDeltaMin_Q15[L];
96 :
97 : } else {
98 : /* Find the lower extreme for the location of the current center frequency */
99 0 : min_center_Q15 = 0;
100 0 : for( k = 0; k < I; k++ ) {
101 0 : min_center_Q15 += NDeltaMin_Q15[k];
102 : }
103 0 : min_center_Q15 += silk_RSHIFT( NDeltaMin_Q15[I], 1 );
104 :
105 : /* Find the upper extreme for the location of the current center frequency */
106 0 : max_center_Q15 = 1 << 15;
107 0 : for( k = L; k > I; k-- ) {
108 0 : max_center_Q15 -= NDeltaMin_Q15[k];
109 : }
110 0 : max_center_Q15 -= silk_RSHIFT( NDeltaMin_Q15[I], 1 );
111 :
112 : /* Move apart, sorted by value, keeping the same center frequency */
113 0 : center_freq_Q15 = (opus_int16)silk_LIMIT_32( silk_RSHIFT_ROUND( (opus_int32)NLSF_Q15[I-1] + (opus_int32)NLSF_Q15[I], 1 ),
114 : min_center_Q15, max_center_Q15 );
115 0 : NLSF_Q15[I-1] = center_freq_Q15 - silk_RSHIFT( NDeltaMin_Q15[I], 1 );
116 0 : NLSF_Q15[I] = NLSF_Q15[I-1] + NDeltaMin_Q15[I];
117 : }
118 : }
119 :
120 : /* Safe and simple fall back method, which is less ideal than the above */
121 0 : if( loops == MAX_LOOPS )
122 : {
123 : /* Insertion sort (fast for already almost sorted arrays): */
124 : /* Best case: O(n) for an already sorted array */
125 : /* Worst case: O(n^2) for an inversely sorted array */
126 0 : silk_insertion_sort_increasing_all_values_int16( &NLSF_Q15[0], L );
127 :
128 : /* First NLSF should be no less than NDeltaMin[0] */
129 0 : NLSF_Q15[0] = silk_max_int( NLSF_Q15[0], NDeltaMin_Q15[0] );
130 :
131 : /* Keep delta_min distance between the NLSFs */
132 0 : for( i = 1; i < L; i++ )
133 0 : NLSF_Q15[i] = silk_max_int( NLSF_Q15[i], silk_ADD_SAT16( NLSF_Q15[i-1], NDeltaMin_Q15[i] ) );
134 :
135 : /* Last NLSF should be no higher than 1 - NDeltaMin[L] */
136 0 : NLSF_Q15[L-1] = silk_min_int( NLSF_Q15[L-1], (1<<15) - NDeltaMin_Q15[L] );
137 :
138 : /* Keep NDeltaMin distance between the NLSFs */
139 0 : for( i = L-2; i >= 0; i-- )
140 0 : NLSF_Q15[i] = silk_min_int( NLSF_Q15[i], NLSF_Q15[i+1] - NDeltaMin_Q15[i+1] );
141 : }
142 : }
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