1 /* 2 * Copyright (c) 2013 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 "vp9/common/vp9_common.h" 12 #include "vp9/common/vp9_entropy.h" 13 14 #include "vp9/encoder/vp9_boolhuff.h" 15 #include "vp9/encoder/vp9_treewriter.h" 16 17 #define vp9_cost_upd ((int)(vp9_cost_one(upd) - vp9_cost_zero(upd)) >> 8) 18 #define vp9_cost_upd256 ((int)(vp9_cost_one(upd) - vp9_cost_zero(upd))) 19 20 static int update_bits[255]; 21 22 static int count_uniform(int v, int n) { 23 int l = get_unsigned_bits(n); 24 int m; 25 if (l == 0) return 0; 26 m = (1 << l) - n; 27 if (v < m) 28 return l - 1; 29 else 30 return l; 31 } 32 33 static int split_index(int i, int n, int modulus) { 34 int max1 = (n - 1 - modulus / 2) / modulus + 1; 35 if (i % modulus == modulus / 2) 36 i = i / modulus; 37 else 38 i = max1 + i - (i + modulus - modulus / 2) / modulus; 39 return i; 40 } 41 42 static int recenter_nonneg(int v, int m) { 43 if (v > (m << 1)) 44 return v; 45 else if (v >= m) 46 return ((v - m) << 1); 47 else 48 return ((m - v) << 1) - 1; 49 } 50 51 static int remap_prob(int v, int m) { 52 int i; 53 static const int map_table[MAX_PROB - 1] = { 54 // generated by: 55 // map_table[j] = split_index(j, MAX_PROB - 1, MODULUS_PARAM); 56 20, 21, 22, 23, 24, 25, 0, 26, 27, 28, 29, 30, 31, 32, 33, 57 34, 35, 36, 37, 1, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 58 48, 49, 2, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 59 3, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 4, 74, 60 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 5, 86, 87, 88, 61 89, 90, 91, 92, 93, 94, 95, 96, 97, 6, 98, 99, 100, 101, 102, 62 103, 104, 105, 106, 107, 108, 109, 7, 110, 111, 112, 113, 114, 115, 116, 63 117, 118, 119, 120, 121, 8, 122, 123, 124, 125, 126, 127, 128, 129, 130, 64 131, 132, 133, 9, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 65 145, 10, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 11, 66 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 12, 170, 171, 67 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 13, 182, 183, 184, 185, 68 186, 187, 188, 189, 190, 191, 192, 193, 14, 194, 195, 196, 197, 198, 199, 69 200, 201, 202, 203, 204, 205, 15, 206, 207, 208, 209, 210, 211, 212, 213, 70 214, 215, 216, 217, 16, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 71 228, 229, 17, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 72 18, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 19, 73 }; 74 v--; 75 m--; 76 if ((m << 1) <= MAX_PROB) 77 i = recenter_nonneg(v, m) - 1; 78 else 79 i = recenter_nonneg(MAX_PROB - 1 - v, MAX_PROB - 1 - m) - 1; 80 81 i = map_table[i]; 82 return i; 83 } 84 85 static int count_term_subexp(int word, int k, int num_syms) { 86 int count = 0; 87 int i = 0; 88 int mk = 0; 89 while (1) { 90 int b = (i ? k + i - 1 : k); 91 int a = (1 << b); 92 if (num_syms <= mk + 3 * a) { 93 count += count_uniform(word - mk, num_syms - mk); 94 break; 95 } else { 96 int t = (word >= mk + a); 97 count++; 98 if (t) { 99 i = i + 1; 100 mk += a; 101 } else { 102 count += b; 103 break; 104 } 105 } 106 } 107 return count; 108 } 109 110 static int prob_diff_update_cost(vp9_prob newp, vp9_prob oldp) { 111 int delp = remap_prob(newp, oldp); 112 return update_bits[delp] * 256; 113 } 114 115 static void encode_uniform(vp9_writer *w, int v, int n) { 116 int l = get_unsigned_bits(n); 117 int m; 118 if (l == 0) 119 return; 120 m = (1 << l) - n; 121 if (v < m) { 122 vp9_write_literal(w, v, l - 1); 123 } else { 124 vp9_write_literal(w, m + ((v - m) >> 1), l - 1); 125 vp9_write_literal(w, (v - m) & 1, 1); 126 } 127 } 128 129 static void encode_term_subexp(vp9_writer *w, int word, int k, int num_syms) { 130 int i = 0; 131 int mk = 0; 132 while (1) { 133 int b = (i ? k + i - 1 : k); 134 int a = (1 << b); 135 if (num_syms <= mk + 3 * a) { 136 encode_uniform(w, word - mk, num_syms - mk); 137 break; 138 } else { 139 int t = (word >= mk + a); 140 vp9_write_literal(w, t, 1); 141 if (t) { 142 i = i + 1; 143 mk += a; 144 } else { 145 vp9_write_literal(w, word - mk, b); 146 break; 147 } 148 } 149 } 150 } 151 152 void vp9_write_prob_diff_update(vp9_writer *w, vp9_prob newp, vp9_prob oldp) { 153 const int delp = remap_prob(newp, oldp); 154 encode_term_subexp(w, delp, SUBEXP_PARAM, 255); 155 } 156 157 void vp9_compute_update_table() { 158 int i; 159 for (i = 0; i < 254; i++) 160 update_bits[i] = count_term_subexp(i, SUBEXP_PARAM, 255); 161 } 162 163 int vp9_prob_diff_update_savings_search(const unsigned int *ct, 164 vp9_prob oldp, vp9_prob *bestp, 165 vp9_prob upd) { 166 const int old_b = cost_branch256(ct, oldp); 167 int bestsavings = 0; 168 vp9_prob newp, bestnewp = oldp; 169 const int step = *bestp > oldp ? -1 : 1; 170 171 for (newp = *bestp; newp != oldp; newp += step) { 172 const int new_b = cost_branch256(ct, newp); 173 const int update_b = prob_diff_update_cost(newp, oldp) + vp9_cost_upd256; 174 const int savings = old_b - new_b - update_b; 175 if (savings > bestsavings) { 176 bestsavings = savings; 177 bestnewp = newp; 178 } 179 } 180 *bestp = bestnewp; 181 return bestsavings; 182 } 183 184 int vp9_prob_diff_update_savings_search_model(const unsigned int *ct, 185 const vp9_prob *oldp, 186 vp9_prob *bestp, 187 vp9_prob upd, 188 int b, int r) { 189 int i, old_b, new_b, update_b, savings, bestsavings, step; 190 int newp; 191 vp9_prob bestnewp, newplist[ENTROPY_NODES], oldplist[ENTROPY_NODES]; 192 vp9_model_to_full_probs(oldp, oldplist); 193 vpx_memcpy(newplist, oldp, sizeof(vp9_prob) * UNCONSTRAINED_NODES); 194 for (i = UNCONSTRAINED_NODES, old_b = 0; i < ENTROPY_NODES; ++i) 195 old_b += cost_branch256(ct + 2 * i, oldplist[i]); 196 old_b += cost_branch256(ct + 2 * PIVOT_NODE, oldplist[PIVOT_NODE]); 197 198 bestsavings = 0; 199 bestnewp = oldp[PIVOT_NODE]; 200 201 step = (*bestp > oldp[PIVOT_NODE] ? -1 : 1); 202 203 for (newp = *bestp; newp != oldp[PIVOT_NODE]; newp += step) { 204 if (newp < 1 || newp > 255) 205 continue; 206 newplist[PIVOT_NODE] = newp; 207 vp9_model_to_full_probs(newplist, newplist); 208 for (i = UNCONSTRAINED_NODES, new_b = 0; i < ENTROPY_NODES; ++i) 209 new_b += cost_branch256(ct + 2 * i, newplist[i]); 210 new_b += cost_branch256(ct + 2 * PIVOT_NODE, newplist[PIVOT_NODE]); 211 update_b = prob_diff_update_cost(newp, oldp[PIVOT_NODE]) + 212 vp9_cost_upd256; 213 savings = old_b - new_b - update_b; 214 if (savings > bestsavings) { 215 bestsavings = savings; 216 bestnewp = newp; 217 } 218 } 219 *bestp = bestnewp; 220 return bestsavings; 221 } 222 223 void vp9_cond_prob_diff_update(vp9_writer *w, vp9_prob *oldp, 224 const unsigned int ct[2]) { 225 const vp9_prob upd = DIFF_UPDATE_PROB; 226 vp9_prob newp = get_binary_prob(ct[0], ct[1]); 227 const int savings = vp9_prob_diff_update_savings_search(ct, *oldp, &newp, 228 upd); 229 assert(newp >= 1); 230 if (savings > 0) { 231 vp9_write(w, 1, upd); 232 vp9_write_prob_diff_update(w, newp, *oldp); 233 *oldp = newp; 234 } else { 235 vp9_write(w, 0, upd); 236 } 237 } 238
