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comparison: media/libopus/silk/NLSF_stabilize.c

media/libopus/silk/NLSF_stabilize.c

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1 /***********************************************************************
2 Copyright (c) 2006-2011, Skype Limited. All rights reserved.
3 Redistribution and use in source and binary forms, with or without
4 modification, are permitted provided that the following conditions
5 are met:
6 - Redistributions of source code must retain the above copyright notice,
7 this list of conditions and the following disclaimer.
8 - Redistributions in binary form must reproduce the above copyright
9 notice, this list of conditions and the following disclaimer in the
10 documentation and/or other materials provided with the distribution.
11 - Neither the name of Internet Society, IETF or IETF Trust, nor the
12 names of specific contributors, may be used to endorse or promote
13 products derived from this software without specific prior written
14 permission.
15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
19 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
20 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
21 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
22 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
23 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
24 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
25 POSSIBILITY OF SUCH DAMAGE.
26 ***********************************************************************/
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 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 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 silk_assert( NDeltaMin_Q15[L] >= 1 );
59
60 for( loops = 0; loops < MAX_LOOPS; loops++ ) {
61 /**************************/
62 /* Find smallest distance */
63 /**************************/
64 /* First element */
65 min_diff_Q15 = NLSF_Q15[0] - NDeltaMin_Q15[0];
66 I = 0;
67 /* Middle elements */
68 for( i = 1; i <= L-1; i++ ) {
69 diff_Q15 = NLSF_Q15[i] - ( NLSF_Q15[i-1] + NDeltaMin_Q15[i] );
70 if( diff_Q15 < min_diff_Q15 ) {
71 min_diff_Q15 = diff_Q15;
72 I = i;
73 }
74 }
75 /* Last element */
76 diff_Q15 = ( 1 << 15 ) - ( NLSF_Q15[L-1] + NDeltaMin_Q15[L] );
77 if( diff_Q15 < min_diff_Q15 ) {
78 min_diff_Q15 = diff_Q15;
79 I = L;
80 }
81
82 /***************************************************/
83 /* Now check if the smallest distance non-negative */
84 /***************************************************/
85 if( min_diff_Q15 >= 0 ) {
86 return;
87 }
88
89 if( I == 0 ) {
90 /* Move away from lower limit */
91 NLSF_Q15[0] = NDeltaMin_Q15[0];
92
93 } else if( I == L) {
94 /* Move away from higher limit */
95 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 min_center_Q15 = 0;
100 for( k = 0; k < I; k++ ) {
101 min_center_Q15 += NDeltaMin_Q15[k];
102 }
103 min_center_Q15 += silk_RSHIFT( NDeltaMin_Q15[I], 1 );
104
105 /* Find the upper extreme for the location of the current center frequency */
106 max_center_Q15 = 1 << 15;
107 for( k = L; k > I; k-- ) {
108 max_center_Q15 -= NDeltaMin_Q15[k];
109 }
110 max_center_Q15 -= silk_RSHIFT( NDeltaMin_Q15[I], 1 );
111
112 /* Move apart, sorted by value, keeping the same center frequency */
113 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 NLSF_Q15[I-1] = center_freq_Q15 - silk_RSHIFT( NDeltaMin_Q15[I], 1 );
116 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 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 silk_insertion_sort_increasing_all_values_int16( &NLSF_Q15[0], L );
127
128 /* First NLSF should be no less than NDeltaMin[0] */
129 NLSF_Q15[0] = silk_max_int( NLSF_Q15[0], NDeltaMin_Q15[0] );
130
131 /* Keep delta_min distance between the NLSFs */
132 for( i = 1; i < L; i++ )
133 NLSF_Q15[i] = silk_max_int( NLSF_Q15[i], NLSF_Q15[i-1] + NDeltaMin_Q15[i] );
134
135 /* Last NLSF should be no higher than 1 - NDeltaMin[L] */
136 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 for( i = L-2; i >= 0; i-- )
140 NLSF_Q15[i] = silk_min_int( NLSF_Q15[i], NLSF_Q15[i+1] - NDeltaMin_Q15[i+1] );
141 }
142 }

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