1*a58d3d2aSXin Li /***********************************************************************
2*a58d3d2aSXin Li Copyright (c) 2013, Koen Vos. All rights reserved.
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4*a58d3d2aSXin Li modification, are permitted provided that the following conditions
5*a58d3d2aSXin Li are met:
6*a58d3d2aSXin Li - Redistributions of source code must retain the above copyright notice,
7*a58d3d2aSXin Li this list of conditions and the following disclaimer.
8*a58d3d2aSXin Li - Redistributions in binary form must reproduce the above copyright
9*a58d3d2aSXin Li notice, this list of conditions and the following disclaimer in the
10*a58d3d2aSXin Li documentation and/or other materials provided with the distribution.
11*a58d3d2aSXin Li - Neither the name of Internet Society, IETF or IETF Trust, nor the
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13*a58d3d2aSXin Li products derived from this software without specific prior written
14*a58d3d2aSXin Li permission.
15*a58d3d2aSXin Li THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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26*a58d3d2aSXin Li ***********************************************************************/
27*a58d3d2aSXin Li
28*a58d3d2aSXin Li #ifdef HAVE_CONFIG_H
29*a58d3d2aSXin Li #include "config.h"
30*a58d3d2aSXin Li #endif
31*a58d3d2aSXin Li
32*a58d3d2aSXin Li #include "SigProc_FIX.h"
33*a58d3d2aSXin Li
34*a58d3d2aSXin Li /* Convert int32 coefficients to int16 coefs and make sure there's no wrap-around.
35*a58d3d2aSXin Li 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*a58d3d2aSXin Li void silk_LPC_fit(
37*a58d3d2aSXin Li opus_int16 *a_QOUT, /* O Output signal */
38*a58d3d2aSXin Li opus_int32 *a_QIN, /* I/O Input signal */
39*a58d3d2aSXin Li const opus_int QOUT, /* I Input Q domain */
40*a58d3d2aSXin Li const opus_int QIN, /* I Input Q domain */
41*a58d3d2aSXin Li const opus_int d /* I Filter order */
42*a58d3d2aSXin Li )
43*a58d3d2aSXin Li {
44*a58d3d2aSXin Li opus_int i, k, idx = 0;
45*a58d3d2aSXin Li opus_int32 maxabs, absval, chirp_Q16;
46*a58d3d2aSXin Li
47*a58d3d2aSXin Li /* Limit the maximum absolute value of the prediction coefficients, so that they'll fit in int16 */
48*a58d3d2aSXin Li for( i = 0; i < 10; i++ ) {
49*a58d3d2aSXin Li /* Find maximum absolute value and its index */
50*a58d3d2aSXin Li maxabs = 0;
51*a58d3d2aSXin Li for( k = 0; k < d; k++ ) {
52*a58d3d2aSXin Li absval = silk_abs( a_QIN[k] );
53*a58d3d2aSXin Li if( absval > maxabs ) {
54*a58d3d2aSXin Li maxabs = absval;
55*a58d3d2aSXin Li idx = k;
56*a58d3d2aSXin Li }
57*a58d3d2aSXin Li }
58*a58d3d2aSXin Li maxabs = silk_RSHIFT_ROUND( maxabs, QIN - QOUT );
59*a58d3d2aSXin Li
60*a58d3d2aSXin Li if( maxabs > silk_int16_MAX ) {
61*a58d3d2aSXin Li /* Reduce magnitude of prediction coefficients */
62*a58d3d2aSXin Li maxabs = silk_min( maxabs, 163838 ); /* ( silk_int32_MAX >> 14 ) + silk_int16_MAX = 163838 */
63*a58d3d2aSXin Li chirp_Q16 = SILK_FIX_CONST( 0.999, 16 ) - silk_DIV32( silk_LSHIFT( maxabs - silk_int16_MAX, 14 ),
64*a58d3d2aSXin Li silk_RSHIFT32( silk_MUL( maxabs, idx + 1), 2 ) );
65*a58d3d2aSXin Li silk_bwexpander_32( a_QIN, d, chirp_Q16 );
66*a58d3d2aSXin Li } else {
67*a58d3d2aSXin Li break;
68*a58d3d2aSXin Li }
69*a58d3d2aSXin Li }
70*a58d3d2aSXin Li
71*a58d3d2aSXin Li if( i == 10 ) {
72*a58d3d2aSXin Li /* Reached the last iteration, clip the coefficients */
73*a58d3d2aSXin Li for( k = 0; k < d; k++ ) {
74*a58d3d2aSXin Li a_QOUT[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT ) );
75*a58d3d2aSXin Li a_QIN[ k ] = silk_LSHIFT( (opus_int32)a_QOUT[ k ], QIN - QOUT );
76*a58d3d2aSXin Li }
77*a58d3d2aSXin Li } else {
78*a58d3d2aSXin Li for( k = 0; k < d; k++ ) {
79*a58d3d2aSXin Li a_QOUT[ k ] = (opus_int16)silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT );
80*a58d3d2aSXin Li }
81*a58d3d2aSXin Li }
82*a58d3d2aSXin Li }
83