ref: 54a3495a5299518368aeeffb675dccd86dc22578
dir: /silk/NLSF_stabilize.c/
/*********************************************************************** Copyright (c) 2006-2011, Skype Limited. All rights reserved. Redistribution and use in source and binary forms, with or without modification, (subject to the limitations in the disclaimer below) are permitted provided that the following conditions are met: - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. - Neither the name of Skype Limited, nor the names of specific contributors, may be used to endorse or promote products derived from this software without specific prior written permission. NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED BY THIS LICENSE. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. ***********************************************************************/ #ifdef HAVE_CONFIG_H #include "config.h" #endif /* NLSF stabilizer: */ /* */ /* - Moves NLSFs futher apart if they are too close */ /* - Moves NLSFs away from borders if they are too close */ /* - High effort to achieve a modification with minimum */ /* Euclidean distance to input vector */ /* - Output are sorted NLSF coefficients */ /* */ #include "SigProc_FIX.h" /* Constant Definitions */ #define MAX_LOOPS 20 /* NLSF stabilizer, for a single input data vector */ void silk_NLSF_stabilize( opus_int16 *NLSF_Q15, /* I/O Unstable/stabilized normalized LSF vector in Q15 [L] */ const opus_int16 *NDeltaMin_Q15, /* I Min distance vector, NDeltaMin_Q15[L] must be >= 1 [L+1] */ const opus_int L /* I Number of NLSF parameters in the input vector */ ) { opus_int i, I=0, k, loops; opus_int16 center_freq_Q15; opus_int32 diff_Q15, min_diff_Q15, min_center_Q15, max_center_Q15; /* This is necessary to ensure an output within range of a opus_int16 */ silk_assert( NDeltaMin_Q15[L] >= 1 ); for( loops = 0; loops < MAX_LOOPS; loops++ ) { /**************************/ /* Find smallest distance */ /**************************/ /* First element */ min_diff_Q15 = NLSF_Q15[0] - NDeltaMin_Q15[0]; I = 0; /* Middle elements */ for( i = 1; i <= L-1; i++ ) { diff_Q15 = NLSF_Q15[i] - ( NLSF_Q15[i-1] + NDeltaMin_Q15[i] ); if( diff_Q15 < min_diff_Q15 ) { min_diff_Q15 = diff_Q15; I = i; } } /* Last element */ diff_Q15 = ( 1 << 15 ) - ( NLSF_Q15[L-1] + NDeltaMin_Q15[L] ); if( diff_Q15 < min_diff_Q15 ) { min_diff_Q15 = diff_Q15; I = L; } /***************************************************/ /* Now check if the smallest distance non-negative */ /***************************************************/ if( min_diff_Q15 >= 0 ) { return; } if( I == 0 ) { /* Move away from lower limit */ NLSF_Q15[0] = NDeltaMin_Q15[0]; } else if( I == L) { /* Move away from higher limit */ NLSF_Q15[L-1] = ( 1 << 15 ) - NDeltaMin_Q15[L]; } else { /* Find the lower extreme for the location of the current center frequency */ min_center_Q15 = 0; for( k = 0; k < I; k++ ) { min_center_Q15 += NDeltaMin_Q15[k]; } min_center_Q15 += silk_RSHIFT( NDeltaMin_Q15[I], 1 ); /* Find the upper extreme for the location of the current center frequency */ max_center_Q15 = 1 << 15; for( k = L; k > I; k-- ) { max_center_Q15 -= NDeltaMin_Q15[k]; } max_center_Q15 -= silk_RSHIFT( NDeltaMin_Q15[I], 1 ); /* Move apart, sorted by value, keeping the same center frequency */ center_freq_Q15 = (opus_int16)silk_LIMIT_32( silk_RSHIFT_ROUND( (opus_int32)NLSF_Q15[I-1] + (opus_int32)NLSF_Q15[I], 1 ), min_center_Q15, max_center_Q15 ); NLSF_Q15[I-1] = center_freq_Q15 - silk_RSHIFT( NDeltaMin_Q15[I], 1 ); NLSF_Q15[I] = NLSF_Q15[I-1] + NDeltaMin_Q15[I]; } } /* Safe and simple fall back method, which is less ideal than the above */ if( loops == MAX_LOOPS ) { /* Insertion sort (fast for already almost sorted arrays): */ /* Best case: O(n) for an already sorted array */ /* Worst case: O(n^2) for an inversely sorted array */ silk_insertion_sort_increasing_all_values_int16( &NLSF_Q15[0], L ); /* First NLSF should be no less than NDeltaMin[0] */ NLSF_Q15[0] = silk_max_int( NLSF_Q15[0], NDeltaMin_Q15[0] ); /* Keep delta_min distance between the NLSFs */ for( i = 1; i < L; i++ ) NLSF_Q15[i] = silk_max_int( NLSF_Q15[i], NLSF_Q15[i-1] + NDeltaMin_Q15[i] ); /* Last NLSF should be no higher than 1 - NDeltaMin[L] */ NLSF_Q15[L-1] = silk_min_int( NLSF_Q15[L-1], (1<<15) - NDeltaMin_Q15[L] ); /* Keep NDeltaMin distance between the NLSFs */ for( i = L-2; i >= 0; i-- ) NLSF_Q15[i] = silk_min_int( NLSF_Q15[i], NLSF_Q15[i+1] - NDeltaMin_Q15[i+1] ); } }