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_FIX.h"
michael@0: 
michael@0: /* Faster than schur64(), but much less accurate.                       */
michael@0: /* uses SMLAWB(), requiring armv5E and higher.                          */
michael@0: opus_int32 silk_schur(                              /* O    Returns residual energy                                     */
michael@0:     opus_int16                  *rc_Q15,            /* O    reflection coefficients [order] Q15                         */
michael@0:     const opus_int32            *c,                 /* I    correlations [order+1]                                      */
michael@0:     const opus_int32            order               /* I    prediction order                                            */
michael@0: )
michael@0: {
michael@0:     opus_int        k, n, lz;
michael@0:     opus_int32    C[ SILK_MAX_ORDER_LPC + 1 ][ 2 ];
michael@0:     opus_int32    Ctmp1, Ctmp2, rc_tmp_Q15;
michael@0: 
michael@0:     silk_assert( order==6||order==8||order==10||order==12||order==14||order==16 );
michael@0: 
michael@0:     /* Get number of leading zeros */
michael@0:     lz = silk_CLZ32( c[ 0 ] );
michael@0: 
michael@0:     /* Copy correlations and adjust level to Q30 */
michael@0:     if( lz < 2 ) {
michael@0:         /* lz must be 1, so shift one to the right */
michael@0:         for( k = 0; k < order + 1; k++ ) {
michael@0:             C[ k ][ 0 ] = C[ k ][ 1 ] = silk_RSHIFT( c[ k ], 1 );
michael@0:         }
michael@0:     } else if( lz > 2 ) {
michael@0:         /* Shift to the left */
michael@0:         lz -= 2;
michael@0:         for( k = 0; k < order + 1; k++ ) {
michael@0:             C[ k ][ 0 ] = C[ k ][ 1 ] = silk_LSHIFT( c[ k ], lz );
michael@0:         }
michael@0:     } else {
michael@0:         /* No need to shift */
michael@0:         for( k = 0; k < order + 1; k++ ) {
michael@0:             C[ k ][ 0 ] = C[ k ][ 1 ] = c[ k ];
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     for( k = 0; k < order; k++ ) {
michael@0:         /* Check that we won't be getting an unstable rc, otherwise stop here. */
michael@0:         if (silk_abs_int32(C[ k + 1 ][ 0 ]) >= C[ 0 ][ 1 ]) {
michael@0:            if ( C[ k + 1 ][ 0 ] > 0 ) {
michael@0:               rc_Q15[ k ] = -SILK_FIX_CONST( .99f, 15 );
michael@0:            } else {
michael@0:               rc_Q15[ k ] = SILK_FIX_CONST( .99f, 15 );
michael@0:            }
michael@0:            k++;
michael@0:            break;
michael@0:         }
michael@0: 
michael@0:         /* Get reflection coefficient */
michael@0:         rc_tmp_Q15 = -silk_DIV32_16( C[ k + 1 ][ 0 ], silk_max_32( silk_RSHIFT( C[ 0 ][ 1 ], 15 ), 1 ) );
michael@0: 
michael@0:         /* Clip (shouldn't happen for properly conditioned inputs) */
michael@0:         rc_tmp_Q15 = silk_SAT16( rc_tmp_Q15 );
michael@0: 
michael@0:         /* Store */
michael@0:         rc_Q15[ k ] = (opus_int16)rc_tmp_Q15;
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 ] = silk_SMLAWB( Ctmp1, silk_LSHIFT( Ctmp2, 1 ), rc_tmp_Q15 );
michael@0:             C[ n ][ 1 ]         = silk_SMLAWB( Ctmp2, silk_LSHIFT( Ctmp1, 1 ), rc_tmp_Q15 );
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     for(; k < order; k++ ) {
michael@0:        rc_Q15[ k ] = 0;
michael@0:     }
michael@0: 
michael@0:     /* return residual energy */
michael@0:     return silk_max_32( 1, C[ 0 ][ 1 ] );
michael@0: }