Chris@69: /***********************************************************************
Chris@69: Copyright (c) 2006-2011, Skype Limited. 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_FLP.h"
Chris@69: 
Chris@69: silk_float silk_schur_FLP(                  /* O    returns residual energy                                     */
Chris@69:     silk_float          refl_coef[],        /* O    reflection coefficients (length order)                      */
Chris@69:     const silk_float    auto_corr[],        /* I    autocorrelation sequence (length order+1)                   */
Chris@69:     opus_int            order               /* I    order                                                       */
Chris@69: )
Chris@69: {
Chris@69:     opus_int   k, n;
Chris@69:     double C[ SILK_MAX_ORDER_LPC + 1 ][ 2 ];
Chris@69:     double Ctmp1, Ctmp2, rc_tmp;
Chris@69: 
Chris@69:     celt_assert( order >= 0 && order <= SILK_MAX_ORDER_LPC );
Chris@69: 
Chris@69:     /* Copy correlations */
Chris@69:     k = 0;
Chris@69:     do {
Chris@69:         C[ k ][ 0 ] = C[ k ][ 1 ] = auto_corr[ k ];
Chris@69:     } while( ++k <= order );
Chris@69: 
Chris@69:     for( k = 0; k < order; k++ ) {
Chris@69:         /* Get reflection coefficient */
Chris@69:         rc_tmp = -C[ k + 1 ][ 0 ] / silk_max_float( C[ 0 ][ 1 ], 1e-9f );
Chris@69: 
Chris@69:         /* Save the output */
Chris@69:         refl_coef[ k ] = (silk_float)rc_tmp;
Chris@69: 
Chris@69:         /* Update correlations */
Chris@69:         for( n = 0; n < order - k; n++ ) {
Chris@69:             Ctmp1 = C[ n + k + 1 ][ 0 ];
Chris@69:             Ctmp2 = C[ n ][ 1 ];
Chris@69:             C[ n + k + 1 ][ 0 ] = Ctmp1 + Ctmp2 * rc_tmp;
Chris@69:             C[ n ][ 1 ]         = Ctmp2 + Ctmp1 * rc_tmp;
Chris@69:         }
Chris@69:     }
Chris@69: 
Chris@69:     /* Return residual energy */
Chris@69:     return (silk_float)C[ 0 ][ 1 ];
Chris@69: }