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_FIX.h"
cannam@154: 
cannam@154: /* Slower than schur(), but more accurate.                              */
cannam@154: /* Uses SMULL(), available on armv4                                     */
cannam@154: opus_int32 silk_schur64(                            /* O    returns residual energy                                     */
cannam@154:     opus_int32                  rc_Q16[],           /* O    Reflection coefficients [order] Q16                         */
cannam@154:     const opus_int32            c[],                /* I    Correlations [order+1]                                      */
cannam@154:     opus_int32                  order               /* I    Prediction order                                            */
cannam@154: )
cannam@154: {
cannam@154:     opus_int   k, n;
cannam@154:     opus_int32 C[ SILK_MAX_ORDER_LPC + 1 ][ 2 ];
cannam@154:     opus_int32 Ctmp1_Q30, Ctmp2_Q30, rc_tmp_Q31;
cannam@154: 
cannam@154:     celt_assert( order >= 0 && order <= SILK_MAX_ORDER_LPC );
cannam@154: 
cannam@154:     /* Check for invalid input */
cannam@154:     if( c[ 0 ] <= 0 ) {
cannam@154:         silk_memset( rc_Q16, 0, order * sizeof( opus_int32 ) );
cannam@154:         return 0;
cannam@154:     }
cannam@154: 
cannam@154:     k = 0;
cannam@154:     do {
cannam@154:         C[ k ][ 0 ] = C[ k ][ 1 ] = c[ k ];
cannam@154:     } while( ++k <= order );
cannam@154: 
cannam@154:     for( k = 0; k < order; k++ ) {
cannam@154:         /* Check that we won't be getting an unstable rc, otherwise stop here. */
cannam@154:         if (silk_abs_int32(C[ k + 1 ][ 0 ]) >= C[ 0 ][ 1 ]) {
cannam@154:            if ( C[ k + 1 ][ 0 ] > 0 ) {
cannam@154:               rc_Q16[ k ] = -SILK_FIX_CONST( .99f, 16 );
cannam@154:            } else {
cannam@154:               rc_Q16[ k ] = SILK_FIX_CONST( .99f, 16 );
cannam@154:            }
cannam@154:            k++;
cannam@154:            break;
cannam@154:         }
cannam@154: 
cannam@154:         /* Get reflection coefficient: divide two Q30 values and get result in Q31 */
cannam@154:         rc_tmp_Q31 = silk_DIV32_varQ( -C[ k + 1 ][ 0 ], C[ 0 ][ 1 ], 31 );
cannam@154: 
cannam@154:         /* Save the output */
cannam@154:         rc_Q16[ k ] = silk_RSHIFT_ROUND( rc_tmp_Q31, 15 );
cannam@154: 
cannam@154:         /* Update correlations */
cannam@154:         for( n = 0; n < order - k; n++ ) {
cannam@154:             Ctmp1_Q30 = C[ n + k + 1 ][ 0 ];
cannam@154:             Ctmp2_Q30 = C[ n ][ 1 ];
cannam@154: 
cannam@154:             /* Multiply and add the highest int32 */
cannam@154:             C[ n + k + 1 ][ 0 ] = Ctmp1_Q30 + silk_SMMUL( silk_LSHIFT( Ctmp2_Q30, 1 ), rc_tmp_Q31 );
cannam@154:             C[ n ][ 1 ]         = Ctmp2_Q30 + silk_SMMUL( silk_LSHIFT( Ctmp1_Q30, 1 ), rc_tmp_Q31 );
cannam@154:         }
cannam@154:     }
cannam@154: 
cannam@154:     for(; k < order; k++ ) {
cannam@154:        rc_Q16[ k ] = 0;
cannam@154:     }
cannam@154: 
cannam@154:     return silk_max_32( 1, C[ 0 ][ 1 ] );
cannam@154: }