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 "main_FLP.h"
michael@0: 
michael@0: /* Autocorrelations for a warped frequency axis */
michael@0: void silk_warped_autocorrelation_FLP(
michael@0:     silk_float                      *corr,                              /* O    Result [order + 1]                          */
michael@0:     const silk_float                *input,                             /* I    Input data to correlate                     */
michael@0:     const silk_float                warping,                            /* I    Warping coefficient                         */
michael@0:     const opus_int                  length,                             /* I    Length of input                             */
michael@0:     const opus_int                  order                               /* I    Correlation order (even)                    */
michael@0: )
michael@0: {
michael@0:     opus_int    n, i;
michael@0:     double      tmp1, tmp2;
michael@0:     double      state[ MAX_SHAPE_LPC_ORDER + 1 ] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 };
michael@0:     double      C[     MAX_SHAPE_LPC_ORDER + 1 ] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 };
michael@0: 
michael@0:     /* Order must be even */
michael@0:     silk_assert( ( order & 1 ) == 0 );
michael@0: 
michael@0:     /* Loop over samples */
michael@0:     for( n = 0; n < length; n++ ) {
michael@0:         tmp1 = input[ n ];
michael@0:         /* Loop over allpass sections */
michael@0:         for( i = 0; i < order; i += 2 ) {
michael@0:             /* Output of allpass section */
michael@0:             tmp2 = state[ i ] + warping * ( state[ i + 1 ] - tmp1 );
michael@0:             state[ i ] = tmp1;
michael@0:             C[ i ] += state[ 0 ] * tmp1;
michael@0:             /* Output of allpass section */
michael@0:             tmp1 = state[ i + 1 ] + warping * ( state[ i + 2 ] - tmp2 );
michael@0:             state[ i + 1 ] = tmp2;
michael@0:             C[ i + 1 ] += state[ 0 ] * tmp2;
michael@0:         }
michael@0:         state[ order ] = tmp1;
michael@0:         C[ order ] += state[ 0 ] * tmp1;
michael@0:     }
michael@0: 
michael@0:     /* Copy correlations in silk_float output format */
michael@0:     for( i = 0; i < order + 1; i++ ) {
michael@0:         corr[ i ] = ( silk_float )C[ i ];
michael@0:     }
michael@0: }