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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_FIX.h"
33 
34 #define QA                          24
35 #define A_LIMIT                     SILK_FIX_CONST( 0.99975, QA )
36 
37 #define MUL32_FRAC_Q(a32, b32, Q)   ((opus_int32)(silk_RSHIFT_ROUND64(silk_SMULL(a32, b32), Q)))
38 
39 /* Compute inverse of LPC prediction gain, and                          */
40 /* test if LPC coefficients are stable (all poles within unit circle)   */
LPC_inverse_pred_gain_QA(opus_int32 A_QA[2][SILK_MAX_ORDER_LPC],const opus_int order)41 static opus_int32 LPC_inverse_pred_gain_QA(                 /* O   Returns inverse prediction gain in energy domain, Q30    */
42     opus_int32           A_QA[ 2 ][ SILK_MAX_ORDER_LPC ],   /* I   Prediction coefficients                                  */
43     const opus_int       order                              /* I   Prediction order                                         */
44 )
45 {
46     opus_int   k, n, mult2Q;
47     opus_int32 invGain_Q30, rc_Q31, rc_mult1_Q30, rc_mult2, tmp_QA;
48     opus_int32 *Aold_QA, *Anew_QA;
49 
50     Anew_QA = A_QA[ order & 1 ];
51 
52     invGain_Q30 = (opus_int32)1 << 30;
53     for( k = order - 1; k > 0; k-- ) {
54         /* Check for stability */
55         if( ( Anew_QA[ k ] > A_LIMIT ) || ( Anew_QA[ k ] < -A_LIMIT ) ) {
56             return 0;
57         }
58 
59         /* Set RC equal to negated AR coef */
60         rc_Q31 = -silk_LSHIFT( Anew_QA[ k ], 31 - QA );
61 
62         /* rc_mult1_Q30 range: [ 1 : 2^30 ] */
63         rc_mult1_Q30 = ( (opus_int32)1 << 30 ) - silk_SMMUL( rc_Q31, rc_Q31 );
64         silk_assert( rc_mult1_Q30 > ( 1 << 15 ) );                   /* reduce A_LIMIT if fails */
65         silk_assert( rc_mult1_Q30 <= ( 1 << 30 ) );
66 
67         /* rc_mult2 range: [ 2^30 : silk_int32_MAX ] */
68         mult2Q = 32 - silk_CLZ32( silk_abs( rc_mult1_Q30 ) );
69         rc_mult2 = silk_INVERSE32_varQ( rc_mult1_Q30, mult2Q + 30 );
70 
71         /* Update inverse gain */
72         /* invGain_Q30 range: [ 0 : 2^30 ] */
73         invGain_Q30 = silk_LSHIFT( silk_SMMUL( invGain_Q30, rc_mult1_Q30 ), 2 );
74         silk_assert( invGain_Q30 >= 0           );
75         silk_assert( invGain_Q30 <= ( 1 << 30 ) );
76 
77         /* Swap pointers */
78         Aold_QA = Anew_QA;
79         Anew_QA = A_QA[ k & 1 ];
80 
81         /* Update AR coefficient */
82         for( n = 0; n < k; n++ ) {
83             tmp_QA = Aold_QA[ n ] - MUL32_FRAC_Q( Aold_QA[ k - n - 1 ], rc_Q31, 31 );
84             Anew_QA[ n ] = MUL32_FRAC_Q( tmp_QA, rc_mult2 , mult2Q );
85         }
86     }
87 
88     /* Check for stability */
89     if( ( Anew_QA[ 0 ] > A_LIMIT ) || ( Anew_QA[ 0 ] < -A_LIMIT ) ) {
90         return 0;
91     }
92 
93     /* Set RC equal to negated AR coef */
94     rc_Q31 = -silk_LSHIFT( Anew_QA[ 0 ], 31 - QA );
95 
96     /* Range: [ 1 : 2^30 ] */
97     rc_mult1_Q30 = ( (opus_int32)1 << 30 ) - silk_SMMUL( rc_Q31, rc_Q31 );
98 
99     /* Update inverse gain */
100     /* Range: [ 0 : 2^30 ] */
101     invGain_Q30 = silk_LSHIFT( silk_SMMUL( invGain_Q30, rc_mult1_Q30 ), 2 );
102     silk_assert( invGain_Q30 >= 0     );
103     silk_assert( invGain_Q30 <= 1<<30 );
104 
105     return invGain_Q30;
106 }
107 
108 /* For input in Q12 domain */
silk_LPC_inverse_pred_gain(const opus_int16 * A_Q12,const opus_int order)109 opus_int32 silk_LPC_inverse_pred_gain(              /* O   Returns inverse prediction gain in energy domain, Q30        */
110     const opus_int16            *A_Q12,             /* I   Prediction coefficients, Q12 [order]                         */
111     const opus_int              order               /* I   Prediction order                                             */
112 )
113 {
114     opus_int   k;
115     opus_int32 Atmp_QA[ 2 ][ SILK_MAX_ORDER_LPC ];
116     opus_int32 *Anew_QA;
117     opus_int32 DC_resp = 0;
118 
119     Anew_QA = Atmp_QA[ order & 1 ];
120 
121     /* Increase Q domain of the AR coefficients */
122     for( k = 0; k < order; k++ ) {
123         DC_resp += (opus_int32)A_Q12[ k ];
124         Anew_QA[ k ] = silk_LSHIFT32( (opus_int32)A_Q12[ k ], QA - 12 );
125     }
126     /* If the DC is unstable, we don't even need to do the full calculations */
127     if( DC_resp >= 4096 ) {
128         return 0;
129     }
130     return LPC_inverse_pred_gain_QA( Atmp_QA, order );
131 }
132 
133 #ifdef FIXED_POINT
134 
135 /* For input in Q24 domain */
silk_LPC_inverse_pred_gain_Q24(const opus_int32 * A_Q24,const opus_int order)136 opus_int32 silk_LPC_inverse_pred_gain_Q24(          /* O    Returns inverse prediction gain in energy domain, Q30       */
137     const opus_int32            *A_Q24,             /* I    Prediction coefficients [order]                             */
138     const opus_int              order               /* I    Prediction order                                            */
139 )
140 {
141     opus_int   k;
142     opus_int32 Atmp_QA[ 2 ][ SILK_MAX_ORDER_LPC ];
143     opus_int32 *Anew_QA;
144 
145     Anew_QA = Atmp_QA[ order & 1 ];
146 
147     /* Increase Q domain of the AR coefficients */
148     for( k = 0; k < order; k++ ) {
149         Anew_QA[ k ] = silk_RSHIFT32( A_Q24[ k ], 24 - QA );
150     }
151 
152     return LPC_inverse_pred_gain_QA( Atmp_QA, order );
153 }
154 #endif
155