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1 /***********************************************************************
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2 Copyright (c) 2013, Koen Vos. All rights reserved.
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3 Redistribution and use in source and binary forms, with or without
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4 modification, are permitted provided that the following conditions
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5 are met:
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6 - Redistributions of source code must retain the above copyright notice,
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7 this list of conditions and the following disclaimer.
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8 - Redistributions in binary form must reproduce the above copyright
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9 notice, this list of conditions and the following disclaimer in the
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10 documentation and/or other materials provided with the distribution.
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11 - Neither the name of Internet Society, IETF or IETF Trust, nor the
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12 names of specific contributors, may be used to endorse or promote
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13 products derived from this software without specific prior written
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14 permission.
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15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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16 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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17 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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18 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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19 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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20 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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21 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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22 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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23 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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24 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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25 POSSIBILITY OF SUCH DAMAGE.
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26 ***********************************************************************/
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27
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28 #ifdef HAVE_CONFIG_H
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29 #include "config.h"
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30 #endif
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31
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32 #include "SigProc_FIX.h"
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33
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34 /* Convert int32 coefficients to int16 coefs and make sure there's no wrap-around */
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35 void silk_LPC_fit(
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36 opus_int16 *a_QOUT, /* O Output signal */
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37 opus_int32 *a_QIN, /* I/O Input signal */
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38 const opus_int QOUT, /* I Input Q domain */
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39 const opus_int QIN, /* I Input Q domain */
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40 const opus_int d /* I Filter order */
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41 )
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42 {
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43 opus_int i, k, idx = 0;
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44 opus_int32 maxabs, absval, chirp_Q16;
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45
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46 /* Limit the maximum absolute value of the prediction coefficients, so that they'll fit in int16 */
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47 for( i = 0; i < 10; i++ ) {
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48 /* Find maximum absolute value and its index */
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49 maxabs = 0;
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50 for( k = 0; k < d; k++ ) {
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51 absval = silk_abs( a_QIN[k] );
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52 if( absval > maxabs ) {
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53 maxabs = absval;
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54 idx = k;
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55 }
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56 }
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57 maxabs = silk_RSHIFT_ROUND( maxabs, QIN - QOUT );
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58
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59 if( maxabs > silk_int16_MAX ) {
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60 /* Reduce magnitude of prediction coefficients */
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61 maxabs = silk_min( maxabs, 163838 ); /* ( silk_int32_MAX >> 14 ) + silk_int16_MAX = 163838 */
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62 chirp_Q16 = SILK_FIX_CONST( 0.999, 16 ) - silk_DIV32( silk_LSHIFT( maxabs - silk_int16_MAX, 14 ),
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63 silk_RSHIFT32( silk_MUL( maxabs, idx + 1), 2 ) );
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64 silk_bwexpander_32( a_QIN, d, chirp_Q16 );
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65 } else {
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66 break;
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67 }
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68 }
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69
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70 if( i == 10 ) {
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71 /* Reached the last iteration, clip the coefficients */
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72 for( k = 0; k < d; k++ ) {
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73 a_QOUT[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT ) );
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74 a_QIN[ k ] = silk_LSHIFT( (opus_int32)a_QOUT[ k ], QIN - QOUT );
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75 }
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76 } else {
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77 for( k = 0; k < d; k++ ) {
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78 a_QOUT[ k ] = (opus_int16)silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT );
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79 }
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80 }
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81 }
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