Chris@69: /***********************************************************************
Chris@69: Copyright (c) 2013, Koen Vos. All rights reserved.
Chris@69: Redistribution and use in source and binary forms, with or without
Chris@69: modification, are permitted provided that the following conditions
Chris@69: are met:
Chris@69: - Redistributions of source code must retain the above copyright notice,
Chris@69: this list of conditions and the following disclaimer.
Chris@69: - Redistributions in binary form must reproduce the above copyright
Chris@69: notice, this list of conditions and the following disclaimer in the
Chris@69: documentation and/or other materials provided with the distribution.
Chris@69: - Neither the name of Internet Society, IETF or IETF Trust, nor the
Chris@69: names of specific contributors, may be used to endorse or promote
Chris@69: products derived from this software without specific prior written
Chris@69: permission.
Chris@69: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
Chris@69: AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
Chris@69: IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
Chris@69: ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
Chris@69: LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
Chris@69: CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
Chris@69: SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
Chris@69: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
Chris@69: CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
Chris@69: ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
Chris@69: POSSIBILITY OF SUCH DAMAGE.
Chris@69: ***********************************************************************/
Chris@69: 
Chris@69: #ifdef HAVE_CONFIG_H
Chris@69: #include "config.h"
Chris@69: #endif
Chris@69: 
Chris@69: #include "SigProc_FIX.h"
Chris@69: 
Chris@69: /* Convert int32 coefficients to int16 coefs and make sure there's no wrap-around */
Chris@69: void silk_LPC_fit(
Chris@69:     opus_int16                  *a_QOUT,            /* O    Output signal                                               */
Chris@69:     opus_int32                    *a_QIN,             /* I/O  Input signal                                                */
Chris@69:     const opus_int              QOUT,               /* I    Input Q domain                                              */
Chris@69:     const opus_int              QIN,                /* I    Input Q domain                                              */
Chris@69:     const opus_int              d                   /* I    Filter order                                                */
Chris@69: )
Chris@69: {
Chris@69:     opus_int    i, k, idx = 0;
Chris@69:     opus_int32    maxabs, absval, chirp_Q16;
Chris@69: 
Chris@69:     /* Limit the maximum absolute value of the prediction coefficients, so that they'll fit in int16 */
Chris@69:     for( i = 0; i < 10; i++ ) {
Chris@69:         /* Find maximum absolute value and its index */
Chris@69:         maxabs = 0;
Chris@69:         for( k = 0; k < d; k++ ) {
Chris@69:             absval = silk_abs( a_QIN[k] );
Chris@69:             if( absval > maxabs ) {
Chris@69:                 maxabs = absval;
Chris@69:                 idx    = k;
Chris@69:             }
Chris@69:         }
Chris@69:         maxabs = silk_RSHIFT_ROUND( maxabs, QIN - QOUT );
Chris@69: 
Chris@69:         if( maxabs > silk_int16_MAX ) {
Chris@69:             /* Reduce magnitude of prediction coefficients */
Chris@69:             maxabs = silk_min( maxabs, 163838 );  /* ( silk_int32_MAX >> 14 ) + silk_int16_MAX = 163838 */
Chris@69:             chirp_Q16 = SILK_FIX_CONST( 0.999, 16 ) - silk_DIV32( silk_LSHIFT( maxabs - silk_int16_MAX, 14 ),
Chris@69:                                         silk_RSHIFT32( silk_MUL( maxabs, idx + 1), 2 ) );
Chris@69:             silk_bwexpander_32( a_QIN, d, chirp_Q16 );
Chris@69:         } else {
Chris@69:             break;
Chris@69:         }
Chris@69:     }
Chris@69: 
Chris@69:     if( i == 10 ) {
Chris@69:         /* Reached the last iteration, clip the coefficients */
Chris@69:         for( k = 0; k < d; k++ ) {
Chris@69:             a_QOUT[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT ) );
Chris@69:             a_QIN[ k ] = silk_LSHIFT( (opus_int32)a_QOUT[ k ], QIN - QOUT );
Chris@69:         }
Chris@69:     } else {
Chris@69:         for( k = 0; k < d; k++ ) {
Chris@69:             a_QOUT[ k ] = (opus_int16)silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT );
Chris@69:         }
Chris@69:     }
Chris@69: }