1/***********************************************************************
2Copyright (c) 2006-2011, Skype Limited. All rights reserved.
3Redistribution and use in source and binary forms, with or without
4modification, are permitted provided that the following conditions
5are met:
6- Redistributions of source code must retain the above copyright notice,
7this list of conditions and the following disclaimer.
8- Redistributions in binary form must reproduce the above copyright
9notice, this list of conditions and the following disclaimer in the
10documentation and/or other materials provided with the distribution.
11- Neither the name of Internet Society, IETF or IETF Trust, nor the
12names of specific contributors, may be used to endorse or promote
13products derived from this software without specific prior written
14permission.
15THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
19LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
20CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
21SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
22INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
23CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
24ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
25POSSIBILITY 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)   */
41static 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 */
109opus_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 */
136opus_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