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: #include "tuning_parameters.h"
michael@0: #include "define.h"
michael@0: 
michael@0: #define MAX_FRAME_SIZE              384 /* subfr_length * nb_subfr = ( 0.005 * 16000 + 16 ) * 4 = 384*/
michael@0: 
michael@0: /* Compute reflection coefficients from input signal */
michael@0: silk_float silk_burg_modified_FLP(          /* O    returns residual energy                                     */
michael@0:     silk_float          A[],                /* O    prediction coefficients (length order)                      */
michael@0:     const silk_float    x[],                /* I    input signal, length: nb_subfr*(D+L_sub)                    */
michael@0:     const silk_float    minInvGain,         /* I    minimum inverse prediction gain                             */
michael@0:     const opus_int      subfr_length,       /* I    input signal subframe length (incl. D preceding samples)    */
michael@0:     const opus_int      nb_subfr,           /* I    number of subframes stacked in x                            */
michael@0:     const opus_int      D                   /* I    order                                                       */
michael@0: )
michael@0: {
michael@0:     opus_int         k, n, s, reached_max_gain;
michael@0:     double           C0, invGain, num, nrg_f, nrg_b, rc, Atmp, tmp1, tmp2;
michael@0:     const silk_float *x_ptr;
michael@0:     double           C_first_row[ SILK_MAX_ORDER_LPC ], C_last_row[ SILK_MAX_ORDER_LPC ];
michael@0:     double           CAf[ SILK_MAX_ORDER_LPC + 1 ], CAb[ SILK_MAX_ORDER_LPC + 1 ];
michael@0:     double           Af[ SILK_MAX_ORDER_LPC ];
michael@0: 
michael@0:     silk_assert( subfr_length * nb_subfr <= MAX_FRAME_SIZE );
michael@0: 
michael@0:     /* Compute autocorrelations, added over subframes */
michael@0:     C0 = silk_energy_FLP( x, nb_subfr * subfr_length );
michael@0:     silk_memset( C_first_row, 0, SILK_MAX_ORDER_LPC * sizeof( double ) );
michael@0:     for( s = 0; s < nb_subfr; s++ ) {
michael@0:         x_ptr = x + s * subfr_length;
michael@0:         for( n = 1; n < D + 1; n++ ) {
michael@0:             C_first_row[ n - 1 ] += silk_inner_product_FLP( x_ptr, x_ptr + n, subfr_length - n );
michael@0:         }
michael@0:     }
michael@0:     silk_memcpy( C_last_row, C_first_row, SILK_MAX_ORDER_LPC * sizeof( double ) );
michael@0: 
michael@0:     /* Initialize */
michael@0:     CAb[ 0 ] = CAf[ 0 ] = C0 + FIND_LPC_COND_FAC * C0 + 1e-9f;
michael@0:     invGain = 1.0f;
michael@0:     reached_max_gain = 0;
michael@0:     for( n = 0; n < D; n++ ) {
michael@0:         /* Update first row of correlation matrix (without first element) */
michael@0:         /* Update last row of correlation matrix (without last element, stored in reversed order) */
michael@0:         /* Update C * Af */
michael@0:         /* Update C * flipud(Af) (stored in reversed order) */
michael@0:         for( s = 0; s < nb_subfr; s++ ) {
michael@0:             x_ptr = x + s * subfr_length;
michael@0:             tmp1 = x_ptr[ n ];
michael@0:             tmp2 = x_ptr[ subfr_length - n - 1 ];
michael@0:             for( k = 0; k < n; k++ ) {
michael@0:                 C_first_row[ k ] -= x_ptr[ n ] * x_ptr[ n - k - 1 ];
michael@0:                 C_last_row[ k ]  -= x_ptr[ subfr_length - n - 1 ] * x_ptr[ subfr_length - n + k ];
michael@0:                 Atmp = Af[ k ];
michael@0:                 tmp1 += x_ptr[ n - k - 1 ] * Atmp;
michael@0:                 tmp2 += x_ptr[ subfr_length - n + k ] * Atmp;
michael@0:             }
michael@0:             for( k = 0; k <= n; k++ ) {
michael@0:                 CAf[ k ] -= tmp1 * x_ptr[ n - k ];
michael@0:                 CAb[ k ] -= tmp2 * x_ptr[ subfr_length - n + k - 1 ];
michael@0:             }
michael@0:         }
michael@0:         tmp1 = C_first_row[ n ];
michael@0:         tmp2 = C_last_row[ n ];
michael@0:         for( k = 0; k < n; k++ ) {
michael@0:             Atmp = Af[ k ];
michael@0:             tmp1 += C_last_row[  n - k - 1 ] * Atmp;
michael@0:             tmp2 += C_first_row[ n - k - 1 ] * Atmp;
michael@0:         }
michael@0:         CAf[ n + 1 ] = tmp1;
michael@0:         CAb[ n + 1 ] = tmp2;
michael@0: 
michael@0:         /* Calculate nominator and denominator for the next order reflection (parcor) coefficient */
michael@0:         num = CAb[ n + 1 ];
michael@0:         nrg_b = CAb[ 0 ];
michael@0:         nrg_f = CAf[ 0 ];
michael@0:         for( k = 0; k < n; k++ ) {
michael@0:             Atmp = Af[ k ];
michael@0:             num   += CAb[ n - k ] * Atmp;
michael@0:             nrg_b += CAb[ k + 1 ] * Atmp;
michael@0:             nrg_f += CAf[ k + 1 ] * Atmp;
michael@0:         }
michael@0:         silk_assert( nrg_f > 0.0 );
michael@0:         silk_assert( nrg_b > 0.0 );
michael@0: 
michael@0:         /* Calculate the next order reflection (parcor) coefficient */
michael@0:         rc = -2.0 * num / ( nrg_f + nrg_b );
michael@0:         silk_assert( rc > -1.0 && rc < 1.0 );
michael@0: 
michael@0:         /* Update inverse prediction gain */
michael@0:         tmp1 = invGain * ( 1.0 - rc * rc );
michael@0:         if( tmp1 <= minInvGain ) {
michael@0:             /* Max prediction gain exceeded; set reflection coefficient such that max prediction gain is exactly hit */
michael@0:             rc = sqrt( 1.0 - minInvGain / invGain );
michael@0:             if( num > 0 ) {
michael@0:                 /* Ensure adjusted reflection coefficients has the original sign */
michael@0:                 rc = -rc;
michael@0:             }
michael@0:             invGain = minInvGain;
michael@0:             reached_max_gain = 1;
michael@0:         } else {
michael@0:             invGain = tmp1;
michael@0:         }
michael@0: 
michael@0:         /* Update the AR coefficients */
michael@0:         for( k = 0; k < (n + 1) >> 1; k++ ) {
michael@0:             tmp1 = Af[ k ];
michael@0:             tmp2 = Af[ n - k - 1 ];
michael@0:             Af[ k ]         = tmp1 + rc * tmp2;
michael@0:             Af[ n - k - 1 ] = tmp2 + rc * tmp1;
michael@0:         }
michael@0:         Af[ n ] = rc;
michael@0: 
michael@0:         if( reached_max_gain ) {
michael@0:             /* Reached max prediction gain; set remaining coefficients to zero and exit loop */
michael@0:             for( k = n + 1; k < D; k++ ) {
michael@0:                 Af[ k ] = 0.0;
michael@0:             }
michael@0:             break;
michael@0:         }
michael@0: 
michael@0:         /* Update C * Af and C * Ab */
michael@0:         for( k = 0; k <= n + 1; k++ ) {
michael@0:             tmp1 = CAf[ k ];
michael@0:             CAf[ k ]          += rc * CAb[ n - k + 1 ];
michael@0:             CAb[ n - k + 1  ] += rc * tmp1;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     if( reached_max_gain ) {
michael@0:         /* Convert to silk_float */
michael@0:         for( k = 0; k < D; k++ ) {
michael@0:             A[ k ] = (silk_float)( -Af[ k ] );
michael@0:         }
michael@0:         /* Subtract energy of preceding samples from C0 */
michael@0:         for( s = 0; s < nb_subfr; s++ ) {
michael@0:             C0 -= silk_energy_FLP( x + s * subfr_length, D );
michael@0:         }
michael@0:         /* Approximate residual energy */
michael@0:         nrg_f = C0 * invGain;
michael@0:     } else {
michael@0:         /* Compute residual energy and store coefficients as silk_float */
michael@0:         nrg_f = CAf[ 0 ];
michael@0:         tmp1 = 1.0;
michael@0:         for( k = 0; k < D; k++ ) {
michael@0:             Atmp = Af[ k ];
michael@0:             nrg_f += CAf[ k + 1 ] * Atmp;
michael@0:             tmp1  += Atmp * Atmp;
michael@0:             A[ k ] = (silk_float)(-Atmp);
michael@0:         }
michael@0:         nrg_f -= FIND_LPC_COND_FAC * C0 * tmp1;
michael@0:     }
michael@0: 
michael@0:     /* Return residual energy */
michael@0:     return (silk_float)nrg_f;
michael@0: }