media/libvpx/vp9/decoder/vp9_dsubexp.c@b8a032363ba2 (annotated)
media/libvpx/vp9/decoder/vp9_dsubexp.c
Thu, 22 Jan 2015 13:21:57 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Thu, 22 Jan 2015 13:21:57 +0100
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
- permissions
- -rw-r--r--
Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6
| michael@0 | 1 | /* |
| michael@0 | 2 | Copyright (c) 2010 The WebM project authors. All Rights Reserved. |
| michael@0 | 3 | * |
| michael@0 | 4 | * Use of this source code is governed by a BSD-style license |
| michael@0 | 5 | * that can be found in the LICENSE file in the root of the source |
| michael@0 | 6 | * tree. An additional intellectual property rights grant can be found |
| michael@0 | 7 | * in the file PATENTS. All contributing project authors may |
| michael@0 | 8 | * be found in the AUTHORS file in the root of the source tree. |
| michael@0 | 9 | */ |
| michael@0 | 10 | |
| michael@0 | 11 | #include "vp9/common/vp9_entropy.h" |
| michael@0 | 12 | |
| michael@0 | 13 | #include "vp9/decoder/vp9_dsubexp.h" |
| michael@0 | 14 | |
| michael@0 | 15 | static int inv_recenter_nonneg(int v, int m) { |
| michael@0 | 16 | if (v > 2 * m) |
| michael@0 | 17 | return v; |
| michael@0 | 18 | |
| michael@0 | 19 | return v % 2 ? m - (v + 1) / 2 : m + v / 2; |
| michael@0 | 20 | } |
| michael@0 | 21 | |
| michael@0 | 22 | static int decode_uniform(vp9_reader *r, int n) { |
| michael@0 | 23 | int v; |
| michael@0 | 24 | const int l = get_unsigned_bits(n); |
| michael@0 | 25 | const int m = (1 << l) - n; |
| michael@0 | 26 | if (!l) |
| michael@0 | 27 | return 0; |
| michael@0 | 28 | |
| michael@0 | 29 | v = vp9_read_literal(r, l - 1); |
| michael@0 | 30 | return v < m ? v : (v << 1) - m + vp9_read_bit(r); |
| michael@0 | 31 | } |
| michael@0 | 32 | |
| michael@0 | 33 | |
| michael@0 | 34 | static int merge_index(int v, int n, int modulus) { |
| michael@0 | 35 | int max1 = (n - 1 - modulus / 2) / modulus + 1; |
| michael@0 | 36 | if (v < max1) { |
| michael@0 | 37 | v = v * modulus + modulus / 2; |
| michael@0 | 38 | } else { |
| michael@0 | 39 | int w; |
| michael@0 | 40 | v -= max1; |
| michael@0 | 41 | w = v; |
| michael@0 | 42 | v += (v + modulus - modulus / 2) / modulus; |
| michael@0 | 43 | while (v % modulus == modulus / 2 || |
| michael@0 | 44 | w != v - (v + modulus - modulus / 2) / modulus) v++; |
| michael@0 | 45 | } |
| michael@0 | 46 | return v; |
| michael@0 | 47 | } |
| michael@0 | 48 | |
| michael@0 | 49 | static int inv_remap_prob(int v, int m) { |
| michael@0 | 50 | static int inv_map_table[MAX_PROB - 1] = { |
| michael@0 | 51 | 6, 19, 32, 45, 58, 71, 84, 97, 110, 123, 136, 149, 162, 175, 188, |
| michael@0 | 52 | 201, 214, 227, 240, 253, 0, 1, 2, 3, 4, 5, 7, 8, 9, 10, |
| michael@0 | 53 | 11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26, |
| michael@0 | 54 | 27, 28, 29, 30, 31, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, |
| michael@0 | 55 | 43, 44, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 59, |
| michael@0 | 56 | 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 72, 73, 74, 75, |
| michael@0 | 57 | 76, 77, 78, 79, 80, 81, 82, 83, 85, 86, 87, 88, 89, 90, 91, |
| michael@0 | 58 | 92, 93, 94, 95, 96, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, |
| michael@0 | 59 | 108, 109, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 124, |
| michael@0 | 60 | 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 137, 138, 139, 140, |
| michael@0 | 61 | 141, 142, 143, 144, 145, 146, 147, 148, 150, 151, 152, 153, 154, 155, 156, |
| michael@0 | 62 | 157, 158, 159, 160, 161, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, |
| michael@0 | 63 | 173, 174, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 189, |
| michael@0 | 64 | 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 202, 203, 204, 205, |
| michael@0 | 65 | 206, 207, 208, 209, 210, 211, 212, 213, 215, 216, 217, 218, 219, 220, 221, |
| michael@0 | 66 | 222, 223, 224, 225, 226, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, |
| michael@0 | 67 | 238, 239, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252 |
| michael@0 | 68 | }; |
| michael@0 | 69 | // The clamp is not necessary for conforming VP9 stream, it is added to |
| michael@0 | 70 | // prevent out of bound access for bad input data |
| michael@0 | 71 | v = clamp(v, 0, 253); |
| michael@0 | 72 | v = inv_map_table[v]; |
| michael@0 | 73 | m--; |
| michael@0 | 74 | if ((m << 1) <= MAX_PROB) { |
| michael@0 | 75 | return 1 + inv_recenter_nonneg(v + 1, m); |
| michael@0 | 76 | } else { |
| michael@0 | 77 | return MAX_PROB - inv_recenter_nonneg(v + 1, MAX_PROB - 1 - m); |
| michael@0 | 78 | } |
| michael@0 | 79 | } |
| michael@0 | 80 | |
| michael@0 | 81 | static int decode_term_subexp(vp9_reader *r, int k, int num_syms) { |
| michael@0 | 82 | int i = 0, mk = 0, word; |
| michael@0 | 83 | while (1) { |
| michael@0 | 84 | const int b = i ? k + i - 1 : k; |
| michael@0 | 85 | const int a = 1 << b; |
| michael@0 | 86 | if (num_syms <= mk + 3 * a) { |
| michael@0 | 87 | word = decode_uniform(r, num_syms - mk) + mk; |
| michael@0 | 88 | break; |
| michael@0 | 89 | } else { |
| michael@0 | 90 | if (vp9_read_bit(r)) { |
| michael@0 | 91 | i++; |
| michael@0 | 92 | mk += a; |
| michael@0 | 93 | } else { |
| michael@0 | 94 | word = vp9_read_literal(r, b) + mk; |
| michael@0 | 95 | break; |
| michael@0 | 96 | } |
| michael@0 | 97 | } |
| michael@0 | 98 | } |
| michael@0 | 99 | return word; |
| michael@0 | 100 | } |
| michael@0 | 101 | |
| michael@0 | 102 | void vp9_diff_update_prob(vp9_reader *r, vp9_prob* p) { |
| michael@0 | 103 | if (vp9_read(r, DIFF_UPDATE_PROB)) { |
| michael@0 | 104 | const int delp = decode_term_subexp(r, SUBEXP_PARAM, 255); |
| michael@0 | 105 | *p = (vp9_prob)inv_remap_prob(delp, *p); |
| michael@0 | 106 | } |
| michael@0 | 107 | } |
