1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/media/libvpx/vp9/decoder/vp9_dsubexp.c Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,107 @@
1.4 +/*
1.5 + Copyright (c) 2010 The WebM project authors. All Rights Reserved.
1.6 + *
1.7 + * Use of this source code is governed by a BSD-style license
1.8 + * that can be found in the LICENSE file in the root of the source
1.9 + * tree. An additional intellectual property rights grant can be found
1.10 + * in the file PATENTS. All contributing project authors may
1.11 + * be found in the AUTHORS file in the root of the source tree.
1.12 + */
1.13 +
1.14 +#include "vp9/common/vp9_entropy.h"
1.15 +
1.16 +#include "vp9/decoder/vp9_dsubexp.h"
1.17 +
1.18 +static int inv_recenter_nonneg(int v, int m) {
1.19 + if (v > 2 * m)
1.20 + return v;
1.21 +
1.22 + return v % 2 ? m - (v + 1) / 2 : m + v / 2;
1.23 +}
1.24 +
1.25 +static int decode_uniform(vp9_reader *r, int n) {
1.26 + int v;
1.27 + const int l = get_unsigned_bits(n);
1.28 + const int m = (1 << l) - n;
1.29 + if (!l)
1.30 + return 0;
1.31 +
1.32 + v = vp9_read_literal(r, l - 1);
1.33 + return v < m ? v : (v << 1) - m + vp9_read_bit(r);
1.34 +}
1.35 +
1.36 +
1.37 +static int merge_index(int v, int n, int modulus) {
1.38 + int max1 = (n - 1 - modulus / 2) / modulus + 1;
1.39 + if (v < max1) {
1.40 + v = v * modulus + modulus / 2;
1.41 + } else {
1.42 + int w;
1.43 + v -= max1;
1.44 + w = v;
1.45 + v += (v + modulus - modulus / 2) / modulus;
1.46 + while (v % modulus == modulus / 2 ||
1.47 + w != v - (v + modulus - modulus / 2) / modulus) v++;
1.48 + }
1.49 + return v;
1.50 +}
1.51 +
1.52 +static int inv_remap_prob(int v, int m) {
1.53 + static int inv_map_table[MAX_PROB - 1] = {
1.54 + 6, 19, 32, 45, 58, 71, 84, 97, 110, 123, 136, 149, 162, 175, 188,
1.55 + 201, 214, 227, 240, 253, 0, 1, 2, 3, 4, 5, 7, 8, 9, 10,
1.56 + 11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26,
1.57 + 27, 28, 29, 30, 31, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42,
1.58 + 43, 44, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 59,
1.59 + 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 72, 73, 74, 75,
1.60 + 76, 77, 78, 79, 80, 81, 82, 83, 85, 86, 87, 88, 89, 90, 91,
1.61 + 92, 93, 94, 95, 96, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107,
1.62 + 108, 109, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 124,
1.63 + 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 137, 138, 139, 140,
1.64 + 141, 142, 143, 144, 145, 146, 147, 148, 150, 151, 152, 153, 154, 155, 156,
1.65 + 157, 158, 159, 160, 161, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172,
1.66 + 173, 174, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 189,
1.67 + 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 202, 203, 204, 205,
1.68 + 206, 207, 208, 209, 210, 211, 212, 213, 215, 216, 217, 218, 219, 220, 221,
1.69 + 222, 223, 224, 225, 226, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237,
1.70 + 238, 239, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252
1.71 + };
1.72 + // The clamp is not necessary for conforming VP9 stream, it is added to
1.73 + // prevent out of bound access for bad input data
1.74 + v = clamp(v, 0, 253);
1.75 + v = inv_map_table[v];
1.76 + m--;
1.77 + if ((m << 1) <= MAX_PROB) {
1.78 + return 1 + inv_recenter_nonneg(v + 1, m);
1.79 + } else {
1.80 + return MAX_PROB - inv_recenter_nonneg(v + 1, MAX_PROB - 1 - m);
1.81 + }
1.82 +}
1.83 +
1.84 +static int decode_term_subexp(vp9_reader *r, int k, int num_syms) {
1.85 + int i = 0, mk = 0, word;
1.86 + while (1) {
1.87 + const int b = i ? k + i - 1 : k;
1.88 + const int a = 1 << b;
1.89 + if (num_syms <= mk + 3 * a) {
1.90 + word = decode_uniform(r, num_syms - mk) + mk;
1.91 + break;
1.92 + } else {
1.93 + if (vp9_read_bit(r)) {
1.94 + i++;
1.95 + mk += a;
1.96 + } else {
1.97 + word = vp9_read_literal(r, b) + mk;
1.98 + break;
1.99 + }
1.100 + }
1.101 + }
1.102 + return word;
1.103 +}
1.104 +
1.105 +void vp9_diff_update_prob(vp9_reader *r, vp9_prob* p) {
1.106 + if (vp9_read(r, DIFF_UPDATE_PROB)) {
1.107 + const int delp = decode_term_subexp(r, SUBEXP_PARAM, 255);
1.108 + *p = (vp9_prob)inv_remap_prob(delp, *p);
1.109 + }
1.110 +}
