Coverage Report

Created: 2024-09-06 07:53

/src/opus/silk/LPC_fit.c
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/***********************************************************************
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Copyright (c) 2013, Koen Vos. 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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#include "SigProc_FIX.h"
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/* Convert int32 coefficients to int16 coefs and make sure there's no wrap-around.
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   This logic is reused in _celt_lpc(). Any bug fixes should also be applied there. */
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void silk_LPC_fit(
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    opus_int16                  *a_QOUT,            /* O    Output signal                                               */
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    opus_int32                    *a_QIN,             /* I/O  Input signal                                                */
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    const opus_int              QOUT,               /* I    Input Q domain                                              */
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    const opus_int              QIN,                /* I    Input Q domain                                              */
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    const opus_int              d                   /* I    Filter order                                                */
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)
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{
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    opus_int    i, k, idx = 0;
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    opus_int32    maxabs, absval, chirp_Q16;
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    /* Limit the maximum absolute value of the prediction coefficients, so that they'll fit in int16 */
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    for( i = 0; i < 10; i++ ) {
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        /* Find maximum absolute value and its index */
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        maxabs = 0;
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        for( k = 0; k < d; k++ ) {
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            absval = silk_abs( a_QIN[k] );
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            if( absval > maxabs ) {
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                maxabs = absval;
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                idx    = k;
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            }
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        }
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        maxabs = silk_RSHIFT_ROUND( maxabs, QIN - QOUT );
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        if( maxabs > silk_int16_MAX ) {
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            /* Reduce magnitude of prediction coefficients */
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            maxabs = silk_min( maxabs, 163838 );  /* ( silk_int32_MAX >> 14 ) + silk_int16_MAX = 163838 */
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            chirp_Q16 = SILK_FIX_CONST( 0.999, 16 ) - silk_DIV32( silk_LSHIFT( maxabs - silk_int16_MAX, 14 ),
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                                        silk_RSHIFT32( silk_MUL( maxabs, idx + 1), 2 ) );
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            silk_bwexpander_32( a_QIN, d, chirp_Q16 );
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        } else {
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            break;
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        }
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    }
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    if( i == 10 ) {
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        /* Reached the last iteration, clip the coefficients */
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        for( k = 0; k < d; k++ ) {
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            a_QOUT[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT ) );
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            a_QIN[ k ] = silk_LSHIFT( (opus_int32)a_QOUT[ k ], QIN - QOUT );
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        }
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    } else {
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        for( k = 0; k < d; k++ ) {
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            a_QOUT[ k ] = (opus_int16)silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT );
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        }
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    }
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}