michael@0: /***********************************************************************
michael@0: Copyright (c) 2006-2011, Skype Limited. All rights reserved.
michael@0: Redistribution and use in source and binary forms, with or without
michael@0: modification, are permitted provided that the following conditions
michael@0: are met:
michael@0: - Redistributions of source code must retain the above copyright notice,
michael@0: this list of conditions and the following disclaimer.
michael@0: - Redistributions in binary form must reproduce the above copyright
michael@0: notice, this list of conditions and the following disclaimer in the
michael@0: documentation and/or other materials provided with the distribution.
michael@0: - Neither the name of Internet Society, IETF or IETF Trust, nor the
michael@0: names of specific contributors, may be used to endorse or promote
michael@0: products derived from this software without specific prior written
michael@0: permission.
michael@0: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
michael@0: AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
michael@0: IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
michael@0: ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
michael@0: LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
michael@0: CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
michael@0: SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
michael@0: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
michael@0: CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
michael@0: ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
michael@0: POSSIBILITY OF SUCH DAMAGE.
michael@0: ***********************************************************************/
michael@0: 
michael@0: #ifdef HAVE_CONFIG_H
michael@0: #include "config.h"
michael@0: #endif
michael@0: 
michael@0: #include "SigProc_FLP.h"
michael@0: 
michael@0: silk_float silk_schur_FLP(                  /* O    returns residual energy                                     */
michael@0:     silk_float          refl_coef[],        /* O    reflection coefficients (length order)                      */
michael@0:     const silk_float    auto_corr[],        /* I    autocorrelation sequence (length order+1)                   */
michael@0:     opus_int            order               /* I    order                                                       */
michael@0: )
michael@0: {
michael@0:     opus_int   k, n;
michael@0:     silk_float C[ SILK_MAX_ORDER_LPC + 1 ][ 2 ];
michael@0:     silk_float Ctmp1, Ctmp2, rc_tmp;
michael@0: 
michael@0:     silk_assert( order==6||order==8||order==10||order==12||order==14||order==16 );
michael@0: 
michael@0:     /* Copy correlations */
michael@0:     for( k = 0; k < order+1; k++ ) {
michael@0:         C[ k ][ 0 ] = C[ k ][ 1 ] = auto_corr[ k ];
michael@0:     }
michael@0: 
michael@0:     for( k = 0; k < order; k++ ) {
michael@0:         /* Get reflection coefficient */
michael@0:         rc_tmp = -C[ k + 1 ][ 0 ] / silk_max_float( C[ 0 ][ 1 ], 1e-9f );
michael@0: 
michael@0:         /* Save the output */
michael@0:         refl_coef[ k ] = rc_tmp;
michael@0: 
michael@0:         /* Update correlations */
michael@0:         for( n = 0; n < order - k; n++ ) {
michael@0:             Ctmp1 = C[ n + k + 1 ][ 0 ];
michael@0:             Ctmp2 = C[ n ][ 1 ];
michael@0:             C[ n + k + 1 ][ 0 ] = Ctmp1 + Ctmp2 * rc_tmp;
michael@0:             C[ n ][ 1 ]         = Ctmp2 + Ctmp1 * rc_tmp;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     /* Return residual energy */
michael@0:     return C[ 0 ][ 1 ];
michael@0: }
michael@0: