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+/***********************************************************************
+Copyright (c) 2006-2011, Skype Limited. All rights reserved.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+- Redistributions of source code must retain the above copyright notice,
+this list of conditions and the following disclaimer.
+- Redistributions in binary form must reproduce the above copyright
+notice, this list of conditions and the following disclaimer in the
+documentation and/or other materials provided with the distribution.
+- Neither the name of Internet Society, IETF or IETF Trust, nor the
+names of specific contributors, may be used to endorse or promote
+products derived from this software without specific prior written
+permission.
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+***********************************************************************/
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "SigProc_FLP.h"
+#include "tuning_parameters.h"
+#include "define.h"
+
+#define MAX_FRAME_SIZE 384 /* subfr_length * nb_subfr = ( 0.005 * 16000 + 16 ) * 4 = 384*/
+
+/* Compute reflection coefficients from input signal */
+silk_float silk_burg_modified_FLP( /* O returns residual energy */
+ silk_float A[], /* O prediction coefficients (length order) */
+ const silk_float x[], /* I input signal, length: nb_subfr*(D+L_sub) */
+ const silk_float minInvGain, /* I minimum inverse prediction gain */
+ const opus_int subfr_length, /* I input signal subframe length (incl. D preceding samples) */
+ const opus_int nb_subfr, /* I number of subframes stacked in x */
+ const opus_int D /* I order */
+)
+{
+ opus_int k, n, s, reached_max_gain;
+ double C0, invGain, num, nrg_f, nrg_b, rc, Atmp, tmp1, tmp2;
+ const silk_float *x_ptr;
+ double C_first_row[ SILK_MAX_ORDER_LPC ], C_last_row[ SILK_MAX_ORDER_LPC ];
+ double CAf[ SILK_MAX_ORDER_LPC + 1 ], CAb[ SILK_MAX_ORDER_LPC + 1 ];
+ double Af[ SILK_MAX_ORDER_LPC ];
+
+ celt_assert( subfr_length * nb_subfr <= MAX_FRAME_SIZE );
+
+ /* Compute autocorrelations, added over subframes */
+ C0 = silk_energy_FLP( x, nb_subfr * subfr_length );
+ silk_memset( C_first_row, 0, SILK_MAX_ORDER_LPC * sizeof( double ) );
+ for( s = 0; s < nb_subfr; s++ ) {
+ x_ptr = x + s * subfr_length;
+ for( n = 1; n < D + 1; n++ ) {
+ C_first_row[ n - 1 ] += silk_inner_product_FLP( x_ptr, x_ptr + n, subfr_length - n );
+ }
+ }
+ silk_memcpy( C_last_row, C_first_row, SILK_MAX_ORDER_LPC * sizeof( double ) );
+
+ /* Initialize */
+ CAb[ 0 ] = CAf[ 0 ] = C0 + FIND_LPC_COND_FAC * C0 + 1e-9f;
+ invGain = 1.0f;
+ reached_max_gain = 0;
+ for( n = 0; n < D; n++ ) {
+ /* Update first row of correlation matrix (without first element) */
+ /* Update last row of correlation matrix (without last element, stored in reversed order) */
+ /* Update C * Af */
+ /* Update C * flipud(Af) (stored in reversed order) */
+ for( s = 0; s < nb_subfr; s++ ) {
+ x_ptr = x + s * subfr_length;
+ tmp1 = x_ptr[ n ];
+ tmp2 = x_ptr[ subfr_length - n - 1 ];
+ for( k = 0; k < n; k++ ) {
+ C_first_row[ k ] -= x_ptr[ n ] * x_ptr[ n - k - 1 ];
+ C_last_row[ k ] -= x_ptr[ subfr_length - n - 1 ] * x_ptr[ subfr_length - n + k ];
+ Atmp = Af[ k ];
+ tmp1 += x_ptr[ n - k - 1 ] * Atmp;
+ tmp2 += x_ptr[ subfr_length - n + k ] * Atmp;
+ }
+ for( k = 0; k <= n; k++ ) {
+ CAf[ k ] -= tmp1 * x_ptr[ n - k ];
+ CAb[ k ] -= tmp2 * x_ptr[ subfr_length - n + k - 1 ];
+ }
+ }
+ tmp1 = C_first_row[ n ];
+ tmp2 = C_last_row[ n ];
+ for( k = 0; k < n; k++ ) {
+ Atmp = Af[ k ];
+ tmp1 += C_last_row[ n - k - 1 ] * Atmp;
+ tmp2 += C_first_row[ n - k - 1 ] * Atmp;
+ }
+ CAf[ n + 1 ] = tmp1;
+ CAb[ n + 1 ] = tmp2;
+
+ /* Calculate nominator and denominator for the next order reflection (parcor) coefficient */
+ num = CAb[ n + 1 ];
+ nrg_b = CAb[ 0 ];
+ nrg_f = CAf[ 0 ];
+ for( k = 0; k < n; k++ ) {
+ Atmp = Af[ k ];
+ num += CAb[ n - k ] * Atmp;
+ nrg_b += CAb[ k + 1 ] * Atmp;
+ nrg_f += CAf[ k + 1 ] * Atmp;
+ }
+ silk_assert( nrg_f > 0.0 );
+ silk_assert( nrg_b > 0.0 );
+
+ /* Calculate the next order reflection (parcor) coefficient */
+ rc = -2.0 * num / ( nrg_f + nrg_b );
+ silk_assert( rc > -1.0 && rc < 1.0 );
+
+ /* Update inverse prediction gain */
+ tmp1 = invGain * ( 1.0 - rc * rc );
+ if( tmp1 <= minInvGain ) {
+ /* Max prediction gain exceeded; set reflection coefficient such that max prediction gain is exactly hit */
+ rc = sqrt( 1.0 - minInvGain / invGain );
+ if( num > 0 ) {
+ /* Ensure adjusted reflection coefficients has the original sign */
+ rc = -rc;
+ }
+ invGain = minInvGain;
+ reached_max_gain = 1;
+ } else {
+ invGain = tmp1;
+ }
+
+ /* Update the AR coefficients */
+ for( k = 0; k < (n + 1) >> 1; k++ ) {
+ tmp1 = Af[ k ];
+ tmp2 = Af[ n - k - 1 ];
+ Af[ k ] = tmp1 + rc * tmp2;
+ Af[ n - k - 1 ] = tmp2 + rc * tmp1;
+ }
+ Af[ n ] = rc;
+
+ if( reached_max_gain ) {
+ /* Reached max prediction gain; set remaining coefficients to zero and exit loop */
+ for( k = n + 1; k < D; k++ ) {
+ Af[ k ] = 0.0;
+ }
+ break;
+ }
+
+ /* Update C * Af and C * Ab */
+ for( k = 0; k <= n + 1; k++ ) {
+ tmp1 = CAf[ k ];
+ CAf[ k ] += rc * CAb[ n - k + 1 ];
+ CAb[ n - k + 1 ] += rc * tmp1;
+ }
+ }
+
+ if( reached_max_gain ) {
+ /* Convert to silk_float */
+ for( k = 0; k < D; k++ ) {
+ A[ k ] = (silk_float)( -Af[ k ] );
+ }
+ /* Subtract energy of preceding samples from C0 */
+ for( s = 0; s < nb_subfr; s++ ) {
+ C0 -= silk_energy_FLP( x + s * subfr_length, D );
+ }
+ /* Approximate residual energy */
+ nrg_f = C0 * invGain;
+ } else {
+ /* Compute residual energy and store coefficients as silk_float */
+ nrg_f = CAf[ 0 ];
+ tmp1 = 1.0;
+ for( k = 0; k < D; k++ ) {
+ Atmp = Af[ k ];
+ nrg_f += CAf[ k + 1 ] * Atmp;
+ tmp1 += Atmp * Atmp;
+ A[ k ] = (silk_float)(-Atmp);
+ }
+ nrg_f -= FIND_LPC_COND_FAC * C0 * tmp1;
+ }
+
+ /* Return residual energy */
+ return (silk_float)nrg_f;
+}