media/libopus/silk/NLSF_stabilize.c

   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], silk_ADD_SAT16( 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 }