ref: 6e124863320ae29a9fb342922fcc937ef2066493
dir: /silk/LPC_fit.c/
/*********************************************************************** Copyright (c) 2013, Koen Vos. All rights reserved. Redistribution and use in source and binary forms, with or without modification, 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 Internet Society, IETF or IETF Trust, nor the names of specific contributors, may be used to endorse or promote products derived from this software without specific prior written permission. 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 #include "SigProc_FIX.h" /* Convert int32 coefficients to int16 coefs and make sure there's no wrap-around */ void silk_LPC_fit( opus_int16 *a_QOUT, /* O Output signal */ opus_int32 *a_QIN, /* I/O Input signal */ const opus_int QOUT, /* I Input Q domain */ const opus_int QIN, /* I Input Q domain */ const opus_int d /* I Filter order */ ) { opus_int i, k, idx = 0; opus_int32 maxabs, absval, chirp_Q16; /* Limit the maximum absolute value of the prediction coefficients, so that they'll fit in int16 */ for( i = 0; i < 10; i++ ) { /* Find maximum absolute value and its index */ maxabs = 0; for( k = 0; k < d; k++ ) { absval = silk_abs( a_QIN[k] ); if( absval > maxabs ) { maxabs = absval; idx = k; } } maxabs = silk_RSHIFT_ROUND( maxabs, QIN - QOUT ); if( maxabs > silk_int16_MAX ) { /* Reduce magnitude of prediction coefficients */ maxabs = silk_min( maxabs, 163838 ); /* ( silk_int32_MAX >> 14 ) + silk_int16_MAX = 163838 */ chirp_Q16 = SILK_FIX_CONST( 0.999, 16 ) - silk_DIV32( silk_LSHIFT( maxabs - silk_int16_MAX, 14 ), silk_RSHIFT32( silk_MUL( maxabs, idx + 1), 2 ) ); silk_bwexpander_32( a_QIN, d, chirp_Q16 ); } else { break; } } if( i == 10 ) { /* Reached the last iteration, clip the coefficients */ for( k = 0; k < d; k++ ) { a_QOUT[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT ) ); a_QIN[ k ] = silk_LSHIFT( (opus_int32)a_QOUT[ k ], QIN - QOUT ); } } else { for( k = 0; k < d; k++ ) { a_QOUT[ k ] = (opus_int16)silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT ); } } }