cannam@154: /***********************************************************************
cannam@154: Copyright (c) 2006-2011, Skype Limited. All rights reserved.
cannam@154: Redistribution and use in source and binary forms, with or without
cannam@154: modification, are permitted provided that the following conditions
cannam@154: are met:
cannam@154: - Redistributions of source code must retain the above copyright notice,
cannam@154: this list of conditions and the following disclaimer.
cannam@154: - Redistributions in binary form must reproduce the above copyright
cannam@154: notice, this list of conditions and the following disclaimer in the
cannam@154: documentation and/or other materials provided with the distribution.
cannam@154: - Neither the name of Internet Society, IETF or IETF Trust, nor the
cannam@154: names of specific contributors, may be used to endorse or promote
cannam@154: products derived from this software without specific prior written
cannam@154: permission.
cannam@154: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
cannam@154: AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
cannam@154: IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
cannam@154: ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
cannam@154: LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
cannam@154: CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
cannam@154: SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
cannam@154: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
cannam@154: CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
cannam@154: ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
cannam@154: POSSIBILITY OF SUCH DAMAGE.
cannam@154: ***********************************************************************/
cannam@154: 
cannam@154: #ifdef HAVE_CONFIG_H
cannam@154: #include "config.h"
cannam@154: #endif
cannam@154: 
cannam@154: #include "SigProc_FLP.h"
cannam@154: 
cannam@154: silk_float silk_schur_FLP(                  /* O    returns residual energy                                     */
cannam@154:     silk_float          refl_coef[],        /* O    reflection coefficients (length order)                      */
cannam@154:     const silk_float    auto_corr[],        /* I    autocorrelation sequence (length order+1)                   */
cannam@154:     opus_int            order               /* I    order                                                       */
cannam@154: )
cannam@154: {
cannam@154:     opus_int   k, n;
cannam@154:     double C[ SILK_MAX_ORDER_LPC + 1 ][ 2 ];
cannam@154:     double Ctmp1, Ctmp2, rc_tmp;
cannam@154: 
cannam@154:     celt_assert( order >= 0 && order <= SILK_MAX_ORDER_LPC );
cannam@154: 
cannam@154:     /* Copy correlations */
cannam@154:     k = 0;
cannam@154:     do {
cannam@154:         C[ k ][ 0 ] = C[ k ][ 1 ] = auto_corr[ k ];
cannam@154:     } while( ++k <= order );
cannam@154: 
cannam@154:     for( k = 0; k < order; k++ ) {
cannam@154:         /* Get reflection coefficient */
cannam@154:         rc_tmp = -C[ k + 1 ][ 0 ] / silk_max_float( C[ 0 ][ 1 ], 1e-9f );
cannam@154: 
cannam@154:         /* Save the output */
cannam@154:         refl_coef[ k ] = (silk_float)rc_tmp;
cannam@154: 
cannam@154:         /* Update correlations */
cannam@154:         for( n = 0; n < order - k; n++ ) {
cannam@154:             Ctmp1 = C[ n + k + 1 ][ 0 ];
cannam@154:             Ctmp2 = C[ n ][ 1 ];
cannam@154:             C[ n + k + 1 ][ 0 ] = Ctmp1 + Ctmp2 * rc_tmp;
cannam@154:             C[ n ][ 1 ]         = Ctmp2 + Ctmp1 * rc_tmp;
cannam@154:         }
cannam@154:     }
cannam@154: 
cannam@154:     /* Return residual energy */
cannam@154:     return (silk_float)C[ 0 ][ 1 ];
cannam@154: }