/src/libvpx/vp9/decoder/vp9_dsubexp.c
Line | Count | Source |
1 | | /* |
2 | | Copyright (c) 2010 The WebM project authors. All Rights Reserved. |
3 | | * |
4 | | * Use of this source code is governed by a BSD-style license |
5 | | * that can be found in the LICENSE file in the root of the source |
6 | | * tree. An additional intellectual property rights grant can be found |
7 | | * in the file PATENTS. All contributing project authors may |
8 | | * be found in the AUTHORS file in the root of the source tree. |
9 | | */ |
10 | | |
11 | | #include <assert.h> |
12 | | |
13 | | #include "vp9/common/vp9_entropy.h" |
14 | | |
15 | | #include "vp9/decoder/vp9_dsubexp.h" |
16 | | |
17 | 274k | static int inv_recenter_nonneg(int v, int m) { |
18 | 274k | if (v > 2 * m) return v; |
19 | | |
20 | 126k | return (v & 1) ? m - ((v + 1) >> 1) : m + (v >> 1); |
21 | 274k | } |
22 | | |
23 | 76.2k | static int decode_uniform(vpx_reader *r) { |
24 | 76.2k | const int l = 8; |
25 | 76.2k | const int m = (1 << l) - 191; |
26 | 76.2k | const int v = vpx_read_literal(r, l - 1); |
27 | 76.2k | return v < m ? v : (v << 1) - m + vpx_read_bit(r); |
28 | 76.2k | } |
29 | | |
30 | 274k | static int inv_remap_prob(int v, int m) { |
31 | 274k | static uint8_t inv_map_table[MAX_PROB] = { |
32 | 274k | 7, 20, 33, 46, 59, 72, 85, 98, 111, 124, 137, 150, 163, 176, 189, |
33 | 274k | 202, 215, 228, 241, 254, 1, 2, 3, 4, 5, 6, 8, 9, 10, 11, |
34 | 274k | 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, |
35 | 274k | 28, 29, 30, 31, 32, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, |
36 | 274k | 44, 45, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 60, |
37 | 274k | 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, |
38 | 274k | 77, 78, 79, 80, 81, 82, 83, 84, 86, 87, 88, 89, 90, 91, 92, |
39 | 274k | 93, 94, 95, 96, 97, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, |
40 | 274k | 109, 110, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 125, |
41 | 274k | 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 138, 139, 140, 141, |
42 | 274k | 142, 143, 144, 145, 146, 147, 148, 149, 151, 152, 153, 154, 155, 156, 157, |
43 | 274k | 158, 159, 160, 161, 162, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, |
44 | 274k | 174, 175, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 190, |
45 | 274k | 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 203, 204, 205, 206, |
46 | 274k | 207, 208, 209, 210, 211, 212, 213, 214, 216, 217, 218, 219, 220, 221, 222, |
47 | 274k | 223, 224, 225, 226, 227, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, |
48 | 274k | 239, 240, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 253 |
49 | 274k | }; |
50 | 274k | assert(v < (int)(sizeof(inv_map_table) / sizeof(inv_map_table[0]))); |
51 | 274k | v = inv_map_table[v]; |
52 | 274k | m--; |
53 | 274k | if ((m << 1) <= MAX_PROB) { |
54 | 187k | return 1 + inv_recenter_nonneg(v, m); |
55 | 187k | } else { |
56 | 86.8k | return MAX_PROB - inv_recenter_nonneg(v, MAX_PROB - 1 - m); |
57 | 86.8k | } |
58 | 274k | } |
59 | | |
60 | 274k | static int decode_term_subexp(vpx_reader *r) { |
61 | 274k | if (!vpx_read_bit(r)) return vpx_read_literal(r, 4); |
62 | 163k | if (!vpx_read_bit(r)) return vpx_read_literal(r, 4) + 16; |
63 | 98.6k | if (!vpx_read_bit(r)) return vpx_read_literal(r, 5) + 32; |
64 | 76.2k | return decode_uniform(r) + 64; |
65 | 98.6k | } |
66 | | |
67 | 19.6M | void vp9_diff_update_prob(vpx_reader *r, vpx_prob *p) { |
68 | 19.6M | if (vpx_read(r, DIFF_UPDATE_PROB)) { |
69 | 274k | const int delp = decode_term_subexp(r); |
70 | 274k | *p = (vpx_prob)inv_remap_prob(delp, *p); |
71 | 274k | } |
72 | 19.6M | } |