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1 /***********************************************************************
2 Copyright (c) 2006-2011, Skype Limited. All rights reserved.
3 Redistribution and use in source and binary forms, with or without
4 modification, are permitted provided that the following conditions
5 are met:
6 - Redistributions of source code must retain the above copyright notice,
7 this list of conditions and the following disclaimer.
8 - Redistributions in binary form must reproduce the above copyright
9 notice, this list of conditions and the following disclaimer in the
10 documentation and/or other materials provided with the distribution.
11 - Neither the name of Internet Society, IETF or IETF Trust, nor the
12 names of specific contributors, may be used to endorse or promote
13 products derived from this software without specific prior written
14 permission.
15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
19 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
20 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
21 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
22 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
23 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
24 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
25 POSSIBILITY OF SUCH DAMAGE.
26 ***********************************************************************/
27 
28 #ifdef HAVE_CONFIG_H
29 #include "config.h"
30 #endif
31 
32 #include "SigProc_FLP.h"
33 #include "tuning_parameters.h"
34 #include "define.h"
35 
36 #define MAX_FRAME_SIZE              384 /* subfr_length * nb_subfr = ( 0.005 * 16000 + 16 ) * 4 = 384*/
37 
38 /* Compute reflection coefficients from input signal */
silk_burg_modified_FLP(silk_float A[],const silk_float x[],const silk_float minInvGain,const opus_int subfr_length,const opus_int nb_subfr,const opus_int D)39 silk_float silk_burg_modified_FLP(          /* O    returns residual energy                                     */
40     silk_float          A[],                /* O    prediction coefficients (length order)                      */
41     const silk_float    x[],                /* I    input signal, length: nb_subfr*(D+L_sub)                    */
42     const silk_float    minInvGain,         /* I    minimum inverse prediction gain                             */
43     const opus_int      subfr_length,       /* I    input signal subframe length (incl. D preceding samples)    */
44     const opus_int      nb_subfr,           /* I    number of subframes stacked in x                            */
45     const opus_int      D                   /* I    order                                                       */
46 )
47 {
48     opus_int         k, n, s, reached_max_gain;
49     double           C0, invGain, num, nrg_f, nrg_b, rc, Atmp, tmp1, tmp2;
50     const silk_float *x_ptr;
51     double           C_first_row[ SILK_MAX_ORDER_LPC ], C_last_row[ SILK_MAX_ORDER_LPC ];
52     double           CAf[ SILK_MAX_ORDER_LPC + 1 ], CAb[ SILK_MAX_ORDER_LPC + 1 ];
53     double           Af[ SILK_MAX_ORDER_LPC ];
54 
55     silk_assert( subfr_length * nb_subfr <= MAX_FRAME_SIZE );
56 
57     /* Compute autocorrelations, added over subframes */
58     C0 = silk_energy_FLP( x, nb_subfr * subfr_length );
59     silk_memset( C_first_row, 0, SILK_MAX_ORDER_LPC * sizeof( double ) );
60     for( s = 0; s < nb_subfr; s++ ) {
61         x_ptr = x + s * subfr_length;
62         for( n = 1; n < D + 1; n++ ) {
63             C_first_row[ n - 1 ] += silk_inner_product_FLP( x_ptr, x_ptr + n, subfr_length - n );
64         }
65     }
66     silk_memcpy( C_last_row, C_first_row, SILK_MAX_ORDER_LPC * sizeof( double ) );
67 
68     /* Initialize */
69     CAb[ 0 ] = CAf[ 0 ] = C0 + FIND_LPC_COND_FAC * C0 + 1e-9f;
70     invGain = 1.0f;
71     reached_max_gain = 0;
72     for( n = 0; n < D; n++ ) {
73         /* Update first row of correlation matrix (without first element) */
74         /* Update last row of correlation matrix (without last element, stored in reversed order) */
75         /* Update C * Af */
76         /* Update C * flipud(Af) (stored in reversed order) */
77         for( s = 0; s < nb_subfr; s++ ) {
78             x_ptr = x + s * subfr_length;
79             tmp1 = x_ptr[ n ];
80             tmp2 = x_ptr[ subfr_length - n - 1 ];
81             for( k = 0; k < n; k++ ) {
82                 C_first_row[ k ] -= x_ptr[ n ] * x_ptr[ n - k - 1 ];
83                 C_last_row[ k ]  -= x_ptr[ subfr_length - n - 1 ] * x_ptr[ subfr_length - n + k ];
84                 Atmp = Af[ k ];
85                 tmp1 += x_ptr[ n - k - 1 ] * Atmp;
86                 tmp2 += x_ptr[ subfr_length - n + k ] * Atmp;
87             }
88             for( k = 0; k <= n; k++ ) {
89                 CAf[ k ] -= tmp1 * x_ptr[ n - k ];
90                 CAb[ k ] -= tmp2 * x_ptr[ subfr_length - n + k - 1 ];
91             }
92         }
93         tmp1 = C_first_row[ n ];
94         tmp2 = C_last_row[ n ];
95         for( k = 0; k < n; k++ ) {
96             Atmp = Af[ k ];
97             tmp1 += C_last_row[  n - k - 1 ] * Atmp;
98             tmp2 += C_first_row[ n - k - 1 ] * Atmp;
99         }
100         CAf[ n + 1 ] = tmp1;
101         CAb[ n + 1 ] = tmp2;
102 
103         /* Calculate nominator and denominator for the next order reflection (parcor) coefficient */
104         num = CAb[ n + 1 ];
105         nrg_b = CAb[ 0 ];
106         nrg_f = CAf[ 0 ];
107         for( k = 0; k < n; k++ ) {
108             Atmp = Af[ k ];
109             num   += CAb[ n - k ] * Atmp;
110             nrg_b += CAb[ k + 1 ] * Atmp;
111             nrg_f += CAf[ k + 1 ] * Atmp;
112         }
113         silk_assert( nrg_f > 0.0 );
114         silk_assert( nrg_b > 0.0 );
115 
116         /* Calculate the next order reflection (parcor) coefficient */
117         rc = -2.0 * num / ( nrg_f + nrg_b );
118         silk_assert( rc > -1.0 && rc < 1.0 );
119 
120         /* Update inverse prediction gain */
121         tmp1 = invGain * ( 1.0 - rc * rc );
122         if( tmp1 <= minInvGain ) {
123             /* Max prediction gain exceeded; set reflection coefficient such that max prediction gain is exactly hit */
124             rc = sqrt( 1.0 - minInvGain / invGain );
125             if( num > 0 ) {
126                 /* Ensure adjusted reflection coefficients has the original sign */
127                 rc = -rc;
128             }
129             invGain = minInvGain;
130             reached_max_gain = 1;
131         } else {
132             invGain = tmp1;
133         }
134 
135         /* Update the AR coefficients */
136         for( k = 0; k < (n + 1) >> 1; k++ ) {
137             tmp1 = Af[ k ];
138             tmp2 = Af[ n - k - 1 ];
139             Af[ k ]         = tmp1 + rc * tmp2;
140             Af[ n - k - 1 ] = tmp2 + rc * tmp1;
141         }
142         Af[ n ] = rc;
143 
144         if( reached_max_gain ) {
145             /* Reached max prediction gain; set remaining coefficients to zero and exit loop */
146             for( k = n + 1; k < D; k++ ) {
147                 Af[ k ] = 0.0;
148             }
149             break;
150         }
151 
152         /* Update C * Af and C * Ab */
153         for( k = 0; k <= n + 1; k++ ) {
154             tmp1 = CAf[ k ];
155             CAf[ k ]          += rc * CAb[ n - k + 1 ];
156             CAb[ n - k + 1  ] += rc * tmp1;
157         }
158     }
159 
160     if( reached_max_gain ) {
161         /* Convert to silk_float */
162         for( k = 0; k < D; k++ ) {
163             A[ k ] = (silk_float)( -Af[ k ] );
164         }
165         /* Subtract energy of preceding samples from C0 */
166         for( s = 0; s < nb_subfr; s++ ) {
167             C0 -= silk_energy_FLP( x + s * subfr_length, D );
168         }
169         /* Approximate residual energy */
170         nrg_f = C0 * invGain;
171     } else {
172         /* Compute residual energy and store coefficients as silk_float */
173         nrg_f = CAf[ 0 ];
174         tmp1 = 1.0;
175         for( k = 0; k < D; k++ ) {
176             Atmp = Af[ k ];
177             nrg_f += CAf[ k + 1 ] * Atmp;
178             tmp1  += Atmp * Atmp;
179             A[ k ] = (silk_float)(-Atmp);
180         }
181         nrg_f -= FIND_LPC_COND_FAC * C0 * tmp1;
182     }
183 
184     /* Return residual energy */
185     return (silk_float)nrg_f;
186 }
187