139 lines
3.6 KiB
C
Executable File
139 lines
3.6 KiB
C
Executable File
/* (C) 2007 Jean-Marc Valin, CSIRO
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*/
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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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- Neither the name of the Xiph.org Foundation nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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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 FOUNDATION OR
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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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int ec_laplace_get_start_freq(int decay)
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{
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int fs = (((ec_uint32)32768)*(16384-decay))/(16384+decay);
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/* Making fs even so we're sure that all the range is used for +/- values */
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fs -= (fs&1);
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return fs;
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}
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void ec_laplace_encode_start(ec_enc *enc, int *value, int decay, int fs)
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{
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int i;
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int fl;
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unsigned int ft;
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int s = 0;
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int val = *value;
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if (val < 0)
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{
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s = 1;
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val = -val;
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}
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ft = 32768;
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fl = -fs;
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for (i=0;i<val;i++)
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{
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int tmp_l, tmp_s;
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tmp_l = fl;
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tmp_s = fs;
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fl += fs*2;
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fs = (fs*(ec_int32)decay)>>14;
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if (fs == 0)
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{
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if (fl+2 <= ft)
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{
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fs = 1;
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} else {
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fs = tmp_s;
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fl = tmp_l;
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if (s)
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*value = -i;
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else
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*value = i;
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break;
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}
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}
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}
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if (fl < 0)
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fl = 0;
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if (s)
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fl += fs;
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ec_encode(enc, fl, fl+fs, ft);
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}
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void ec_laplace_encode(ec_enc *enc, int *value, int decay)
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{
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int fs = ec_laplace_get_start_freq(decay);
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ec_laplace_encode_start(enc, value, decay, fs);
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}
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int ec_laplace_decode_start(ec_dec *dec, int decay, int fs)
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{
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int val=0;
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int fl, fh, fm;
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unsigned int ft;
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fl = 0;
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ft = 32768;
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fh = fs;
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fm = ec_decode(dec, ft);
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while (fm >= fh && fs != 0)
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{
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fl = fh;
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fs = (fs*(ec_int32)decay)>>14;
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if (fs == 0 && fh+2 <= ft)
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{
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fs = 1;
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}
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fh += fs*2;
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val++;
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}
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if (fl>0)
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{
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if (fm >= fl+fs)
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{
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val = -val;
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fl += fs;
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} else {
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fh -= fs;
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}
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}
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/* Preventing an infinite loop in case something screws up in the decoding */
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if (fl==fh)
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fl--;
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ec_dec_update(dec, fl, fh, ft);
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return val;
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}
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int ec_laplace_decode(ec_dec *dec, int decay)
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{
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int fs = ec_laplace_get_start_freq(decay);
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return ec_laplace_decode_start(dec, decay, fs);
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}
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