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comparison: media/libopus/silk/LPC_inv_pred_gain.c

media/libopus/silk/LPC_inv_pred_gain.c

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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) */
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 */
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 */
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

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