Line data    Source code

       1             : /* Copyright (c) 2007 CSIRO
       2             :    Copyright (c) 2007-2009 Xiph.Org Foundation
       3             :    Written by Jean-Marc Valin */
       4             : /*
       5             :    Redistribution and use in source and binary forms, with or without
       6             :    modification, are permitted provided that the following conditions
       7             :    are met:
       8             : 
       9             :    - Redistributions of source code must retain the above copyright
      10             :    notice, this list of conditions and the following disclaimer.
      11             : 
      12             :    - Redistributions in binary form must reproduce the above copyright
      13             :    notice, this list of conditions and the following disclaimer in the
      14             :    documentation and/or other materials provided with the distribution.
      15             : 
      16             :    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
      17             :    ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
      18             :    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
      19             :    A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
      20             :    OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
      21             :    EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
      22             :    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
      23             :    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
      24             :    LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
      25             :    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
      26             :    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
      27             : */
      28             : 
      29             : #ifdef HAVE_CONFIG_H
      30             : #include "config.h"
      31             : #endif
      32             : 
      33             : #include "laplace.h"
      34             : #include "mathops.h"
      35             : 
      36             : /* The minimum probability of an energy delta (out of 32768). */
      37             : #define LAPLACE_LOG_MINP (0)
      38             : #define LAPLACE_MINP (1<<LAPLACE_LOG_MINP)
      39             : /* The minimum number of guaranteed representable energy deltas (in one
      40             :     direction). */
      41             : #define LAPLACE_NMIN (16)
      42             : 
      43             : /* When called, decay is positive and at most 11456. */
      44           0 : static unsigned ec_laplace_get_freq1(unsigned fs0, int decay)
      45             : {
      46             :    unsigned ft;
      47           0 :    ft = 32768 - LAPLACE_MINP*(2*LAPLACE_NMIN) - fs0;
      48           0 :    return ft*(opus_int32)(16384-decay)>>15;
      49             : }
      50             : 
      51           0 : void ec_laplace_encode(ec_enc *enc, int *value, unsigned fs, int decay)
      52             : {
      53             :    unsigned fl;
      54           0 :    int val = *value;
      55           0 :    fl = 0;
      56           0 :    if (val)
      57             :    {
      58             :       int s;
      59             :       int i;
      60           0 :       s = -(val<0);
      61           0 :       val = (val+s)^s;
      62           0 :       fl = fs;
      63           0 :       fs = ec_laplace_get_freq1(fs, decay);
      64             :       /* Search the decaying part of the PDF.*/
      65           0 :       for (i=1; fs > 0 && i < val; i++)
      66             :       {
      67           0 :          fs *= 2;
      68           0 :          fl += fs+2*LAPLACE_MINP;
      69           0 :          fs = (fs*(opus_int32)decay)>>15;
      70             :       }
      71             :       /* Everything beyond that has probability LAPLACE_MINP. */
      72           0 :       if (!fs)
      73             :       {
      74             :          int di;
      75             :          int ndi_max;
      76           0 :          ndi_max = (32768-fl+LAPLACE_MINP-1)>>LAPLACE_LOG_MINP;
      77           0 :          ndi_max = (ndi_max-s)>>1;
      78           0 :          di = IMIN(val - i, ndi_max - 1);
      79           0 :          fl += (2*di+1+s)*LAPLACE_MINP;
      80           0 :          fs = IMIN(LAPLACE_MINP, 32768-fl);
      81           0 :          *value = (i+di+s)^s;
      82             :       }
      83             :       else
      84             :       {
      85           0 :          fs += LAPLACE_MINP;
      86           0 :          fl += fs&~s;
      87             :       }
      88           0 :       celt_assert(fl+fs<=32768);
      89           0 :       celt_assert(fs>0);
      90             :    }
      91           0 :    ec_encode_bin(enc, fl, fl+fs, 15);
      92           0 : }
      93             : 
      94           0 : int ec_laplace_decode(ec_dec *dec, unsigned fs, int decay)
      95             : {
      96           0 :    int val=0;
      97             :    unsigned fl;
      98             :    unsigned fm;
      99           0 :    fm = ec_decode_bin(dec, 15);
     100           0 :    fl = 0;
     101           0 :    if (fm >= fs)
     102             :    {
     103           0 :       val++;
     104           0 :       fl = fs;
     105           0 :       fs = ec_laplace_get_freq1(fs, decay)+LAPLACE_MINP;
     106             :       /* Search the decaying part of the PDF.*/
     107           0 :       while(fs > LAPLACE_MINP && fm >= fl+2*fs)
     108             :       {
     109           0 :          fs *= 2;
     110           0 :          fl += fs;
     111           0 :          fs = ((fs-2*LAPLACE_MINP)*(opus_int32)decay)>>15;
     112           0 :          fs += LAPLACE_MINP;
     113           0 :          val++;
     114             :       }
     115             :       /* Everything beyond that has probability LAPLACE_MINP. */
     116           0 :       if (fs <= LAPLACE_MINP)
     117             :       {
     118             :          int di;
     119           0 :          di = (fm-fl)>>(LAPLACE_LOG_MINP+1);
     120           0 :          val += di;
     121           0 :          fl += 2*di*LAPLACE_MINP;
     122             :       }
     123           0 :       if (fm < fl+fs)
     124           0 :          val = -val;
     125             :       else
     126           0 :          fl += fs;
     127             :    }
     128           0 :    celt_assert(fl<32768);
     129           0 :    celt_assert(fs>0);
     130           0 :    celt_assert(fl<=fm);
     131           0 :    celt_assert(fm<IMIN(fl+fs,32768));
     132           0 :    ec_dec_update(dec, fl, IMIN(fl+fs,32768), 32768);
     133           0 :    return val;
     134             : }