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https://github.com/xiph/opus.git
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93 lines
2.9 KiB
C
93 lines
2.9 KiB
C
/* Copyright (c) 2009-2010 Xiph.Org Foundation
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Written by Jean-Marc Valin */
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/*
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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
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notice, 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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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
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OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE 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 "celt_lpc.h"
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#include "arch.h"
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#include "common.h"
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#include "pitch.h"
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float _celt_lpc(
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opus_val16 *_lpc, /* out: [0...p-1] LPC coefficients */
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opus_val16 *rc,
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const opus_val32 *ac, /* in: [0...p] autocorrelation values */
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int p
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)
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{
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int i, j;
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opus_val32 r;
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opus_val32 error = ac[0];
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#ifdef FIXED_POINT
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opus_val32 lpc[LPC_ORDER];
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#else
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float *lpc = _lpc;
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#endif
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RNN_CLEAR(lpc, p);
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RNN_CLEAR(rc, p);
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if (ac[0] != 0)
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{
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for (i = 0; i < p; i++) {
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/* Sum up this iteration's reflection coefficient */
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opus_val32 rr = 0;
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for (j = 0; j < i; j++)
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rr += MULT32_32_Q31(lpc[j],ac[i - j]);
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rr += SHR32(ac[i + 1],3);
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r = -SHL32(rr,3)/error;
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rc[i] = r;
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/* Update LPC coefficients and total error */
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lpc[i] = SHR32(r,3);
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for (j = 0; j < (i+1)>>1; j++)
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{
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opus_val32 tmp1, tmp2;
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tmp1 = lpc[j];
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tmp2 = lpc[i-1-j];
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lpc[j] = tmp1 + MULT32_32_Q31(r,tmp2);
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lpc[i-1-j] = tmp2 + MULT32_32_Q31(r,tmp1);
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}
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error = error - MULT32_32_Q31(MULT32_32_Q31(r,r),error);
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/* Bail out once we get 30 dB gain */
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#ifdef FIXED_POINT
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if (error<SHR32(ac[0],10))
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break;
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#else
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if (error<.001f*ac[0])
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break;
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#endif
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}
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}
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#ifdef FIXED_POINT
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for (i=0;i<p;i++)
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_lpc[i] = ROUND16(lpc[i],16);
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#endif
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return error;
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}
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