81 lines
3.9 KiB
C
81 lines
3.9 KiB
C
/***********************************************************************
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Copyright (c) 2013, Koen Vos. All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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- Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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- Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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- Neither the name of Internet Society, IETF or IETF Trust, nor the
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names of specific contributors, may be used to endorse or promote
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products derived from this software without specific prior written
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permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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***********************************************************************/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include "SigProc_FIX.h"
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/* Convert int32 coefficients to int16 coefs and make sure there's no wrap-around */
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void silk_LPC_fit(
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opus_int16 *a_QOUT, /* O Output signal */
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opus_int32 *a_QIN, /* I/O Input signal */
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const opus_int QOUT, /* I Input Q domain */
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const opus_int QIN, /* I Input Q domain */
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const opus_int d /* I Filter order */
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)
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{
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opus_int i, k, idx = 0;
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opus_int32 maxabs, absval, chirp_Q16;
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/* Limit the maximum absolute value of the prediction coefficients, so that they'll fit in int16 */
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for( i = 0; i < 10; i++ ) {
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/* Find maximum absolute value and its index */
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maxabs = 0;
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for( k = 0; k < d; k++ ) {
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absval = silk_abs( a_QIN[k] );
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if( absval > maxabs ) {
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maxabs = absval;
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idx = k;
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}
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}
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maxabs = silk_RSHIFT_ROUND( maxabs, QIN - QOUT );
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if( maxabs > silk_int16_MAX ) {
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/* Reduce magnitude of prediction coefficients */
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maxabs = silk_min( maxabs, 163838 ); /* ( silk_int32_MAX >> 14 ) + silk_int16_MAX = 163838 */
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chirp_Q16 = SILK_FIX_CONST( 0.999, 16 ) - silk_DIV32( silk_LSHIFT( maxabs - silk_int16_MAX, 14 ),
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silk_RSHIFT32( silk_MUL( maxabs, idx + 1), 2 ) );
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silk_bwexpander_32( a_QIN, d, chirp_Q16 );
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} else {
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break;
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}
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}
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if( i == 10 ) {
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/* Reached the last iteration, clip the coefficients */
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for( k = 0; k < d; k++ ) {
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a_QOUT[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT ) );
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a_QIN[ k ] = silk_LSHIFT( (opus_int32)a_QOUT[ k ], QIN - QOUT );
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}
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} else {
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for( k = 0; k < d; k++ ) {
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a_QOUT[ k ] = (opus_int16)silk_RSHIFT_ROUND( a_QIN[ k ], QIN - QOUT );
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}
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}
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}
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