142 lines
6.2 KiB
C
142 lines
6.2 KiB
C
/***********************************************************************
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Copyright (c) 2006-2011, Skype Limited. All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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- Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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- Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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- Neither the name of Internet Society, IETF or IETF Trust, nor the
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names of specific contributors, may be used to endorse or promote
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products derived from this software without specific prior written
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permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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***********************************************************************/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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/* NLSF stabilizer: */
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/* */
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/* - Moves NLSFs further apart if they are too close */
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/* - Moves NLSFs away from borders if they are too close */
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/* - High effort to achieve a modification with minimum */
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/* Euclidean distance to input vector */
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/* - Output are sorted NLSF coefficients */
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/* */
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#include "SigProc_FIX.h"
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/* Constant Definitions */
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#define MAX_LOOPS 20
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/* NLSF stabilizer, for a single input data vector */
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void silk_NLSF_stabilize(
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opus_int16 *NLSF_Q15, /* I/O Unstable/stabilized normalized LSF vector in Q15 [L] */
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const opus_int16 *NDeltaMin_Q15, /* I Min distance vector, NDeltaMin_Q15[L] must be >= 1 [L+1] */
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const opus_int L /* I Number of NLSF parameters in the input vector */
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)
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{
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opus_int i, I=0, k, loops;
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opus_int16 center_freq_Q15;
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opus_int32 diff_Q15, min_diff_Q15, min_center_Q15, max_center_Q15;
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/* This is necessary to ensure an output within range of a opus_int16 */
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silk_assert( NDeltaMin_Q15[L] >= 1 );
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for( loops = 0; loops < MAX_LOOPS; loops++ ) {
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/**************************/
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/* Find smallest distance */
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/**************************/
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/* First element */
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min_diff_Q15 = NLSF_Q15[0] - NDeltaMin_Q15[0];
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I = 0;
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/* Middle elements */
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for( i = 1; i <= L-1; i++ ) {
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diff_Q15 = NLSF_Q15[i] - ( NLSF_Q15[i-1] + NDeltaMin_Q15[i] );
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if( diff_Q15 < min_diff_Q15 ) {
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min_diff_Q15 = diff_Q15;
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I = i;
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}
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}
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/* Last element */
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diff_Q15 = ( 1 << 15 ) - ( NLSF_Q15[L-1] + NDeltaMin_Q15[L] );
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if( diff_Q15 < min_diff_Q15 ) {
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min_diff_Q15 = diff_Q15;
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I = L;
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}
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/***************************************************/
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/* Now check if the smallest distance non-negative */
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/***************************************************/
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if( min_diff_Q15 >= 0 ) {
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return;
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}
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if( I == 0 ) {
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/* Move away from lower limit */
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NLSF_Q15[0] = NDeltaMin_Q15[0];
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} else if( I == L) {
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/* Move away from higher limit */
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NLSF_Q15[L-1] = ( 1 << 15 ) - NDeltaMin_Q15[L];
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} else {
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/* Find the lower extreme for the location of the current center frequency */
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min_center_Q15 = 0;
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for( k = 0; k < I; k++ ) {
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min_center_Q15 += NDeltaMin_Q15[k];
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}
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min_center_Q15 += silk_RSHIFT( NDeltaMin_Q15[I], 1 );
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/* Find the upper extreme for the location of the current center frequency */
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max_center_Q15 = 1 << 15;
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for( k = L; k > I; k-- ) {
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max_center_Q15 -= NDeltaMin_Q15[k];
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}
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max_center_Q15 -= silk_RSHIFT( NDeltaMin_Q15[I], 1 );
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/* Move apart, sorted by value, keeping the same center frequency */
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center_freq_Q15 = (opus_int16)silk_LIMIT_32( silk_RSHIFT_ROUND( (opus_int32)NLSF_Q15[I-1] + (opus_int32)NLSF_Q15[I], 1 ),
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min_center_Q15, max_center_Q15 );
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NLSF_Q15[I-1] = center_freq_Q15 - silk_RSHIFT( NDeltaMin_Q15[I], 1 );
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NLSF_Q15[I] = NLSF_Q15[I-1] + NDeltaMin_Q15[I];
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}
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}
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/* Safe and simple fall back method, which is less ideal than the above */
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if( loops == MAX_LOOPS )
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{
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/* Insertion sort (fast for already almost sorted arrays): */
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/* Best case: O(n) for an already sorted array */
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/* Worst case: O(n^2) for an inversely sorted array */
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silk_insertion_sort_increasing_all_values_int16( &NLSF_Q15[0], L );
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/* First NLSF should be no less than NDeltaMin[0] */
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NLSF_Q15[0] = silk_max_int( NLSF_Q15[0], NDeltaMin_Q15[0] );
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/* Keep delta_min distance between the NLSFs */
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for( i = 1; i < L; i++ )
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NLSF_Q15[i] = silk_max_int( NLSF_Q15[i], silk_ADD_SAT16( NLSF_Q15[i-1], NDeltaMin_Q15[i] ) );
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/* Last NLSF should be no higher than 1 - NDeltaMin[L] */
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NLSF_Q15[L-1] = silk_min_int( NLSF_Q15[L-1], (1<<15) - NDeltaMin_Q15[L] );
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/* Keep NDeltaMin distance between the NLSFs */
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for( i = L-2; i >= 0; i-- )
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NLSF_Q15[i] = silk_min_int( NLSF_Q15[i], NLSF_Q15[i+1] - NDeltaMin_Q15[i+1] );
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}
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}
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