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. */
ec_laplace_get_freq1(unsigned fs0,int decay)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
ec_laplace_encode(ec_enc * enc,int * value,unsigned fs,int decay)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
ec_laplace_decode(ec_dec * dec,unsigned fs,int decay)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 }
135