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