| /*********************************************************************** |
| 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 ); |
| } |
| } |
| } |
