1 /***********************************************************************
2 Copyright (c) 2013, Koen Vos. 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
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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 /* Convert int32 coefficients to int16 coefs and make sure there's no wrap-around.
35 This logic is reused in _celt_lpc(). Any bug fixes should also be applied there. */
silk_LPC_fit(opus_int16 * a_QOUT,opus_int32 * a_QIN,const opus_int QOUT,const opus_int QIN,const opus_int d)36 void silk_LPC_fit(
37 opus_int16 *a_QOUT, /* O Output signal */
38 opus_int32 *a_QIN, /* I/O Input signal */
39 const opus_int QOUT, /* I Input Q domain */
40 const opus_int QIN, /* I Input Q domain */
41 const opus_int d /* I Filter order */
42 )
43 {
44 opus_int i, k, idx = 0;
45 opus_int32 maxabs, absval, chirp_Q16;
46
47 /* Limit the maximum absolute value of the prediction coefficients, so that they'll fit in int16 */
48 for( i = 0; i < 10; i++ ) {
49 /* Find maximum absolute value and its index */
50 maxabs = 0;
51 for( k = 0; k < d; k++ ) {
52 absval = silk_abs( a_QIN[k] );
53 if( absval > maxabs ) {
54 maxabs = absval;
55 idx = k;
56 }
57 }
58 maxabs = silk_RSHIFT_ROUND( maxabs, QIN - QOUT );
59
60 if( maxabs > silk_int16_MAX ) {
61 /* Reduce magnitude of prediction coefficients */
62 maxabs = silk_min( maxabs, 163838 ); /* ( silk_int32_MAX >> 14 ) + silk_int16_MAX = 163838 */
63 chirp_Q16 = SILK_FIX_CONST( 0.999, 16 ) - silk_DIV32( silk_LSHIFT( maxabs - silk_int16_MAX, 14 ),
64 silk_RSHIFT32( silk_MUL( maxabs, idx + 1), 2 ) );
65 silk_bwexpander_32( a_QIN, d, chirp_Q16 );
66 } else {
67 break;
68 }
69 }
70
71 if( i == 10 ) {
72 /* Reached the last iteration, clip the coefficients */
73 for( k = 0; k < d; k++ ) {
74 a_QOUT[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT ) );
75 a_QIN[ k ] = silk_LSHIFT( (opus_int32)a_QOUT[ k ], QIN - QOUT );
76 }
77 } else {
78 for( k = 0; k < d; k++ ) {
79 a_QOUT[ k ] = (opus_int16)silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT );
80 }
81 }
82 }
83