135 lines
3.9 KiB
C
135 lines
3.9 KiB
C
/* Copyright (c) 2007 CSIRO
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Copyright (c) 2007-2009 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 "laplace.h"
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#include "mathops.h"
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/* The minimum probability of an energy delta (out of 32768). */
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#define LAPLACE_LOG_MINP (0)
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#define LAPLACE_MINP (1<<LAPLACE_LOG_MINP)
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/* The minimum number of guaranteed representable energy deltas (in one
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direction). */
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#define LAPLACE_NMIN (16)
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/* When called, decay is positive and at most 11456. */
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static unsigned ec_laplace_get_freq1(unsigned fs0, int decay)
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{
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unsigned ft;
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ft = 32768 - LAPLACE_MINP*(2*LAPLACE_NMIN) - fs0;
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return ft*(opus_int32)(16384-decay)>>15;
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}
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void ec_laplace_encode(ec_enc *enc, int *value, unsigned fs, int decay)
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{
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unsigned fl;
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int val = *value;
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fl = 0;
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if (val)
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{
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int s;
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int i;
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s = -(val<0);
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val = (val+s)^s;
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fl = fs;
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fs = ec_laplace_get_freq1(fs, decay);
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/* Search the decaying part of the PDF.*/
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for (i=1; fs > 0 && i < val; i++)
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{
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fs *= 2;
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fl += fs+2*LAPLACE_MINP;
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fs = (fs*(opus_int32)decay)>>15;
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}
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/* Everything beyond that has probability LAPLACE_MINP. */
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if (!fs)
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{
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int di;
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int ndi_max;
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ndi_max = (32768-fl+LAPLACE_MINP-1)>>LAPLACE_LOG_MINP;
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ndi_max = (ndi_max-s)>>1;
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di = IMIN(val - i, ndi_max - 1);
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fl += (2*di+1+s)*LAPLACE_MINP;
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fs = IMIN(LAPLACE_MINP, 32768-fl);
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*value = (i+di+s)^s;
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}
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else
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{
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fs += LAPLACE_MINP;
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fl += fs&~s;
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}
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celt_assert(fl+fs<=32768);
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celt_assert(fs>0);
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}
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ec_encode_bin(enc, fl, fl+fs, 15);
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}
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int ec_laplace_decode(ec_dec *dec, unsigned fs, int decay)
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{
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int val=0;
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unsigned fl;
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unsigned fm;
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fm = ec_decode_bin(dec, 15);
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fl = 0;
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if (fm >= fs)
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{
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val++;
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fl = fs;
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fs = ec_laplace_get_freq1(fs, decay)+LAPLACE_MINP;
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/* Search the decaying part of the PDF.*/
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while(fs > LAPLACE_MINP && fm >= fl+2*fs)
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{
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fs *= 2;
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fl += fs;
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fs = ((fs-2*LAPLACE_MINP)*(opus_int32)decay)>>15;
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fs += LAPLACE_MINP;
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val++;
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}
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/* Everything beyond that has probability LAPLACE_MINP. */
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if (fs <= LAPLACE_MINP)
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{
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int di;
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di = (fm-fl)>>(LAPLACE_LOG_MINP+1);
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val += di;
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fl += 2*di*LAPLACE_MINP;
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}
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if (fm < fl+fs)
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val = -val;
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else
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fl += fs;
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}
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celt_assert(fl<32768);
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celt_assert(fs>0);
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celt_assert(fl<=fm);
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celt_assert(fm<IMIN(fl+fs,32768));
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ec_dec_update(dec, fl, IMIN(fl+fs,32768), 32768);
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return val;
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}
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