Line data Source code
1 : /* Copyright (c) 2001-2011 Timothy B. Terriberry
2 : */
3 : /*
4 : Redistribution and use in source and binary forms, with or without
5 : modification, are permitted provided that the following conditions
6 : are met:
7 :
8 : - Redistributions of source code must retain the above copyright
9 : notice, this list of conditions and the following disclaimer.
10 :
11 : - Redistributions in binary form must reproduce the above copyright
12 : notice, this list of conditions and the following disclaimer in the
13 : documentation and/or other materials provided with the distribution.
14 :
15 : THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 : ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 : LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
18 : A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
19 : OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
20 : EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
21 : PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
22 : PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
23 : LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
24 : NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
25 : SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 : */
27 :
28 : #ifdef HAVE_CONFIG_H
29 : #include "config.h"
30 : #endif
31 :
32 : #include "entcode.h"
33 : #include "arch.h"
34 :
35 : #if !defined(EC_CLZ)
36 : /*This is a fallback for systems where we don't know how to access
37 : a BSR or CLZ instruction (see ecintrin.h).
38 : If you are optimizing Opus on a new platform and it has a native CLZ or
39 : BZR (e.g. cell, MIPS, x86, etc) then making it available to Opus will be
40 : an easy performance win.*/
41 : int ec_ilog(opus_uint32 _v){
42 : /*On a Pentium M, this branchless version tested as the fastest on
43 : 1,000,000,000 random 32-bit integers, edging out a similar version with
44 : branches, and a 256-entry LUT version.*/
45 : int ret;
46 : int m;
47 : ret=!!_v;
48 : m=!!(_v&0xFFFF0000)<<4;
49 : _v>>=m;
50 : ret|=m;
51 : m=!!(_v&0xFF00)<<3;
52 : _v>>=m;
53 : ret|=m;
54 : m=!!(_v&0xF0)<<2;
55 : _v>>=m;
56 : ret|=m;
57 : m=!!(_v&0xC)<<1;
58 : _v>>=m;
59 : ret|=m;
60 : ret+=!!(_v&0x2);
61 : return ret;
62 : }
63 : #endif
64 :
65 : #if 1
66 : /* This is a faster version of ec_tell_frac() that takes advantage
67 : of the low (1/8 bit) resolution to use just a linear function
68 : followed by a lookup to determine the exact transition thresholds. */
69 0 : opus_uint32 ec_tell_frac(ec_ctx *_this){
70 : static const unsigned correction[8] =
71 : {35733, 38967, 42495, 46340,
72 : 50535, 55109, 60097, 65535};
73 : opus_uint32 nbits;
74 : opus_uint32 r;
75 : int l;
76 : unsigned b;
77 0 : nbits=_this->nbits_total<<BITRES;
78 0 : l=EC_ILOG(_this->rng);
79 0 : r=_this->rng>>(l-16);
80 0 : b = (r>>12)-8;
81 0 : b += r>correction[b];
82 0 : l = (l<<3)+b;
83 0 : return nbits-l;
84 : }
85 : #else
86 : opus_uint32 ec_tell_frac(ec_ctx *_this){
87 : opus_uint32 nbits;
88 : opus_uint32 r;
89 : int l;
90 : int i;
91 : /*To handle the non-integral number of bits still left in the encoder/decoder
92 : state, we compute the worst-case number of bits of val that must be
93 : encoded to ensure that the value is inside the range for any possible
94 : subsequent bits.
95 : The computation here is independent of val itself (the decoder does not
96 : even track that value), even though the real number of bits used after
97 : ec_enc_done() may be 1 smaller if rng is a power of two and the
98 : corresponding trailing bits of val are all zeros.
99 : If we did try to track that special case, then coding a value with a
100 : probability of 1/(1<<n) might sometimes appear to use more than n bits.
101 : This may help explain the surprising result that a newly initialized
102 : encoder or decoder claims to have used 1 bit.*/
103 : nbits=_this->nbits_total<<BITRES;
104 : l=EC_ILOG(_this->rng);
105 : r=_this->rng>>(l-16);
106 : for(i=BITRES;i-->0;){
107 : int b;
108 : r=r*r>>15;
109 : b=(int)(r>>16);
110 : l=l<<1|b;
111 : r>>=b;
112 : }
113 : return nbits-l;
114 : }
115 : #endif
116 :
117 : #ifdef USE_SMALL_DIV_TABLE
118 : /* Result of 2^32/(2*i+1), except for i=0. */
119 : const opus_uint32 SMALL_DIV_TABLE[129] = {
120 : 0xFFFFFFFF, 0x55555555, 0x33333333, 0x24924924,
121 : 0x1C71C71C, 0x1745D174, 0x13B13B13, 0x11111111,
122 : 0x0F0F0F0F, 0x0D79435E, 0x0C30C30C, 0x0B21642C,
123 : 0x0A3D70A3, 0x097B425E, 0x08D3DCB0, 0x08421084,
124 : 0x07C1F07C, 0x07507507, 0x06EB3E45, 0x06906906,
125 : 0x063E7063, 0x05F417D0, 0x05B05B05, 0x0572620A,
126 : 0x05397829, 0x05050505, 0x04D4873E, 0x04A7904A,
127 : 0x047DC11F, 0x0456C797, 0x04325C53, 0x04104104,
128 : 0x03F03F03, 0x03D22635, 0x03B5CC0E, 0x039B0AD1,
129 : 0x0381C0E0, 0x0369D036, 0x03531DEC, 0x033D91D2,
130 : 0x0329161F, 0x03159721, 0x03030303, 0x02F14990,
131 : 0x02E05C0B, 0x02D02D02, 0x02C0B02C, 0x02B1DA46,
132 : 0x02A3A0FD, 0x0295FAD4, 0x0288DF0C, 0x027C4597,
133 : 0x02702702, 0x02647C69, 0x02593F69, 0x024E6A17,
134 : 0x0243F6F0, 0x0239E0D5, 0x02302302, 0x0226B902,
135 : 0x021D9EAD, 0x0214D021, 0x020C49BA, 0x02040810,
136 : 0x01FC07F0, 0x01F44659, 0x01ECC07B, 0x01E573AC,
137 : 0x01DE5D6E, 0x01D77B65, 0x01D0CB58, 0x01CA4B30,
138 : 0x01C3F8F0, 0x01BDD2B8, 0x01B7D6C3, 0x01B20364,
139 : 0x01AC5701, 0x01A6D01A, 0x01A16D3F, 0x019C2D14,
140 : 0x01970E4F, 0x01920FB4, 0x018D3018, 0x01886E5F,
141 : 0x0183C977, 0x017F405F, 0x017AD220, 0x01767DCE,
142 : 0x01724287, 0x016E1F76, 0x016A13CD, 0x01661EC6,
143 : 0x01623FA7, 0x015E75BB, 0x015AC056, 0x01571ED3,
144 : 0x01539094, 0x01501501, 0x014CAB88, 0x0149539E,
145 : 0x01460CBC, 0x0142D662, 0x013FB013, 0x013C995A,
146 : 0x013991C2, 0x013698DF, 0x0133AE45, 0x0130D190,
147 : 0x012E025C, 0x012B404A, 0x01288B01, 0x0125E227,
148 : 0x01234567, 0x0120B470, 0x011E2EF3, 0x011BB4A4,
149 : 0x01194538, 0x0116E068, 0x011485F0, 0x0112358E,
150 : 0x010FEF01, 0x010DB20A, 0x010B7E6E, 0x010953F3,
151 : 0x01073260, 0x0105197F, 0x0103091B, 0x01010101
152 : };
153 : #endif
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