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 /* Faster than schur64(), but much less accurate. */
35 /* uses SMLAWB(), requiring armv5E and higher. */
silk_schur(opus_int16 * rc_Q15,const opus_int32 * c,const opus_int32 order)36 opus_int32 silk_schur( /* O Returns residual energy */
37 opus_int16 *rc_Q15, /* O reflection coefficients [order] Q15 */
38 const opus_int32 *c, /* I correlations [order+1] */
39 const opus_int32 order /* I prediction order */
40 )
41 {
42 opus_int k, n, lz;
43 opus_int32 C[ SILK_MAX_ORDER_LPC + 1 ][ 2 ];
44 opus_int32 Ctmp1, Ctmp2, rc_tmp_Q15;
45
46 celt_assert( order >= 0 && order <= SILK_MAX_ORDER_LPC );
47
48 /* Get number of leading zeros */
49 lz = silk_CLZ32( c[ 0 ] );
50
51 /* Copy correlations and adjust level to Q30 */
52 k = 0;
53 if( lz < 2 ) {
54 /* lz must be 1, so shift one to the right */
55 do {
56 C[ k ][ 0 ] = C[ k ][ 1 ] = silk_RSHIFT( c[ k ], 1 );
57 } while( ++k <= order );
58 } else if( lz > 2 ) {
59 /* Shift to the left */
60 lz -= 2;
61 do {
62 C[ k ][ 0 ] = C[ k ][ 1 ] = silk_LSHIFT( c[ k ], lz );
63 } while( ++k <= order );
64 } else {
65 /* No need to shift */
66 do {
67 C[ k ][ 0 ] = C[ k ][ 1 ] = c[ k ];
68 } while( ++k <= order );
69 }
70
71 for( k = 0; k < order; k++ ) {
72 /* Check that we won't be getting an unstable rc, otherwise stop here. */
73 if (silk_abs_int32(C[ k + 1 ][ 0 ]) >= C[ 0 ][ 1 ]) {
74 if ( C[ k + 1 ][ 0 ] > 0 ) {
75 rc_Q15[ k ] = -SILK_FIX_CONST( .99f, 15 );
76 } else {
77 rc_Q15[ k ] = SILK_FIX_CONST( .99f, 15 );
78 }
79 k++;
80 break;
81 }
82
83 /* Get reflection coefficient */
84 rc_tmp_Q15 = -silk_DIV32_16( C[ k + 1 ][ 0 ], silk_max_32( silk_RSHIFT( C[ 0 ][ 1 ], 15 ), 1 ) );
85
86 /* Clip (shouldn't happen for properly conditioned inputs) */
87 rc_tmp_Q15 = silk_SAT16( rc_tmp_Q15 );
88
89 /* Store */
90 rc_Q15[ k ] = (opus_int16)rc_tmp_Q15;
91
92 /* Update correlations */
93 for( n = 0; n < order - k; n++ ) {
94 Ctmp1 = C[ n + k + 1 ][ 0 ];
95 Ctmp2 = C[ n ][ 1 ];
96 C[ n + k + 1 ][ 0 ] = silk_SMLAWB( Ctmp1, silk_LSHIFT( Ctmp2, 1 ), rc_tmp_Q15 );
97 C[ n ][ 1 ] = silk_SMLAWB( Ctmp2, silk_LSHIFT( Ctmp1, 1 ), rc_tmp_Q15 );
98 }
99 }
100
101 for(; k < order; k++ ) {
102 rc_Q15[ k ] = 0;
103 }
104
105 /* return residual energy */
106 return silk_max_32( 1, C[ 0 ][ 1 ] );
107 }
108