Alexandre Lision | 744f742 | 2013-09-25 11:39:37 -0400 | [diff] [blame] | 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 | static unsigned ec_laplace_get_freq1(unsigned fs0, int decay) |
| 45 | { |
| 46 | unsigned ft; |
| 47 | ft = 32768 - LAPLACE_MINP*(2*LAPLACE_NMIN) - fs0; |
| 48 | return ft*(opus_int32)(16384-decay)>>15; |
| 49 | } |
| 50 | |
| 51 | void ec_laplace_encode(ec_enc *enc, int *value, unsigned fs, int decay) |
| 52 | { |
| 53 | unsigned fl; |
| 54 | int val = *value; |
| 55 | fl = 0; |
| 56 | if (val) |
| 57 | { |
| 58 | int s; |
| 59 | int i; |
| 60 | s = -(val<0); |
| 61 | val = (val+s)^s; |
| 62 | fl = fs; |
| 63 | fs = ec_laplace_get_freq1(fs, decay); |
| 64 | /* Search the decaying part of the PDF.*/ |
| 65 | for (i=1; fs > 0 && i < val; i++) |
| 66 | { |
| 67 | fs *= 2; |
| 68 | fl += fs+2*LAPLACE_MINP; |
| 69 | fs = (fs*(opus_int32)decay)>>15; |
| 70 | } |
| 71 | /* Everything beyond that has probability LAPLACE_MINP. */ |
| 72 | if (!fs) |
| 73 | { |
| 74 | int di; |
| 75 | int ndi_max; |
| 76 | ndi_max = (32768-fl+LAPLACE_MINP-1)>>LAPLACE_LOG_MINP; |
| 77 | ndi_max = (ndi_max-s)>>1; |
| 78 | di = IMIN(val - i, ndi_max - 1); |
| 79 | fl += (2*di+1+s)*LAPLACE_MINP; |
| 80 | fs = IMIN(LAPLACE_MINP, 32768-fl); |
| 81 | *value = (i+di+s)^s; |
| 82 | } |
| 83 | else |
| 84 | { |
| 85 | fs += LAPLACE_MINP; |
| 86 | fl += fs&~s; |
| 87 | } |
| 88 | celt_assert(fl+fs<=32768); |
| 89 | celt_assert(fs>0); |
| 90 | } |
| 91 | ec_encode_bin(enc, fl, fl+fs, 15); |
| 92 | } |
| 93 | |
| 94 | int ec_laplace_decode(ec_dec *dec, unsigned fs, int decay) |
| 95 | { |
| 96 | int val=0; |
| 97 | unsigned fl; |
| 98 | unsigned fm; |
| 99 | fm = ec_decode_bin(dec, 15); |
| 100 | fl = 0; |
| 101 | if (fm >= fs) |
| 102 | { |
| 103 | val++; |
| 104 | fl = fs; |
| 105 | fs = ec_laplace_get_freq1(fs, decay)+LAPLACE_MINP; |
| 106 | /* Search the decaying part of the PDF.*/ |
| 107 | while(fs > LAPLACE_MINP && fm >= fl+2*fs) |
| 108 | { |
| 109 | fs *= 2; |
| 110 | fl += fs; |
| 111 | fs = ((fs-2*LAPLACE_MINP)*(opus_int32)decay)>>15; |
| 112 | fs += LAPLACE_MINP; |
| 113 | val++; |
| 114 | } |
| 115 | /* Everything beyond that has probability LAPLACE_MINP. */ |
| 116 | if (fs <= LAPLACE_MINP) |
| 117 | { |
| 118 | int di; |
| 119 | di = (fm-fl)>>(LAPLACE_LOG_MINP+1); |
| 120 | val += di; |
| 121 | fl += 2*di*LAPLACE_MINP; |
| 122 | } |
| 123 | if (fm < fl+fs) |
| 124 | val = -val; |
| 125 | else |
| 126 | fl += fs; |
| 127 | } |
| 128 | celt_assert(fl<32768); |
| 129 | celt_assert(fs>0); |
| 130 | celt_assert(fl<=fm); |
| 131 | celt_assert(fm<IMIN(fl+fs,32768)); |
| 132 | ec_dec_update(dec, fl, IMIN(fl+fs,32768), 32768); |
| 133 | return val; |
| 134 | } |