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Deb Mukherjee authored
Uses mapping tables instead of complicated modulo/division operations for prob mapping for forward updates. No bit-stream or output change. Change-Id: Ifd9ce8ac1437835c305c94f64c18273c7a68f546
9c20cedd
/* * Copyright (c) 2013 The WebM project authors. All Rights Reserved. * * Use of this source code is governed by a BSD-style license * that can be found in the LICENSE file in the root of the source * tree. An additional intellectual property rights grant can be found * in the file PATENTS. All contributing project authors may * be found in the AUTHORS file in the root of the source tree. */#include "vp9/common/vp9_common.h"#include "vp9/common/vp9_entropy.h"#include "vp9/encoder/vp9_boolhuff.h"#include "vp9/encoder/vp9_treewriter.h"#define vp9_cost_upd ((int)(vp9_cost_one(upd) - vp9_cost_zero(upd)) >> 8)#define vp9_cost_upd256 ((int)(vp9_cost_one(upd) - vp9_cost_zero(upd)))static int update_bits[255];static int count_uniform(int v, int n) { int l = get_unsigned_bits(n); int m; if (l == 0) return 0; m = (1 << l) - n; if (v < m) return l - 1; else return l;}static int split_index(int i, int n, int modulus) { int max1 = (n - 1 - modulus / 2) / modulus + 1; if (i % modulus == modulus / 2) i = i / modulus; else i = max1 + i - (i + modulus - modulus / 2) / modulus; return i;}static int recenter_nonneg(int v, int m) { if (v > (m << 1)) return v; else if (v >= m) return ((v - m) << 1); else return ((m - v) << 1) - 1;}static int remap_prob(int v, int m) { int i; static int map_table[MAX_PROB - 1] = { // generated by: // map_table[j] = split_index(j, MAX_PROB - 1, MODULUS_PARAM); 20, 21, 22, 23, 24, 25, 0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 1, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 2, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 3, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 4, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 5, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 6, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 7, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 8, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 9, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 10, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 11, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 12, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 13, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 14, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 15, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 16, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227,7172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140
228, 229, 17, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241,
18, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 19,
};
v--;
m--;
if ((m << 1) <= MAX_PROB)
i = recenter_nonneg(v, m) - 1;
else
i = recenter_nonneg(MAX_PROB - 1 - v, MAX_PROB - 1 - m) - 1;
i = map_table[i];
return i;
}
static int count_term_subexp(int word, int k, int num_syms) {
int count = 0;
int i = 0;
int mk = 0;
while (1) {
int b = (i ? k + i - 1 : k);
int a = (1 << b);
if (num_syms <= mk + 3 * a) {
count += count_uniform(word - mk, num_syms - mk);
break;
} else {
int t = (word >= mk + a);
count++;
if (t) {
i = i + 1;
mk += a;
} else {
count += b;
break;
}
}
}
return count;
}
static int prob_diff_update_cost(vp9_prob newp, vp9_prob oldp) {
int delp = remap_prob(newp, oldp);
return update_bits[delp] * 256;
}
static void encode_uniform(vp9_writer *w, int v, int n) {
int l = get_unsigned_bits(n);
int m;
if (l == 0)
return;
m = (1 << l) - n;
if (v < m) {
vp9_write_literal(w, v, l - 1);
} else {
vp9_write_literal(w, m + ((v - m) >> 1), l - 1);
vp9_write_literal(w, (v - m) & 1, 1);
}
}
static void encode_term_subexp(vp9_writer *w, int word, int k, int num_syms) {
int i = 0;
int mk = 0;
while (1) {
int b = (i ? k + i - 1 : k);
int a = (1 << b);
if (num_syms <= mk + 3 * a) {
encode_uniform(w, word - mk, num_syms - mk);
break;
} else {
int t = (word >= mk + a);
vp9_write_literal(w, t, 1);
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if (t) {
i = i + 1;
mk += a;
} else {
vp9_write_literal(w, word - mk, b);
break;
}
}
}
}
void vp9_write_prob_diff_update(vp9_writer *w, vp9_prob newp, vp9_prob oldp) {
const int delp = remap_prob(newp, oldp);
encode_term_subexp(w, delp, SUBEXP_PARAM, 255);
}
void vp9_compute_update_table() {
int i;
for (i = 0; i < 254; i++)
update_bits[i] = count_term_subexp(i, SUBEXP_PARAM, 255);
}
int vp9_prob_diff_update_savings_search(const unsigned int *ct,
vp9_prob oldp, vp9_prob *bestp,
vp9_prob upd) {
const int old_b = cost_branch256(ct, oldp);
int bestsavings = 0;
vp9_prob newp, bestnewp = oldp;
const int step = *bestp > oldp ? -1 : 1;
for (newp = *bestp; newp != oldp; newp += step) {
const int new_b = cost_branch256(ct, newp);
const int update_b = prob_diff_update_cost(newp, oldp) + vp9_cost_upd256;
const int savings = old_b - new_b - update_b;
if (savings > bestsavings) {
bestsavings = savings;
bestnewp = newp;
}
}
*bestp = bestnewp;
return bestsavings;
}
int vp9_prob_diff_update_savings_search_model(const unsigned int *ct,
const vp9_prob *oldp,
vp9_prob *bestp,
vp9_prob upd,
int b, int r) {
int i, old_b, new_b, update_b, savings, bestsavings, step;
int newp;
vp9_prob bestnewp, newplist[ENTROPY_NODES], oldplist[ENTROPY_NODES];
vp9_model_to_full_probs(oldp, oldplist);
vpx_memcpy(newplist, oldp, sizeof(vp9_prob) * UNCONSTRAINED_NODES);
for (i = UNCONSTRAINED_NODES, old_b = 0; i < ENTROPY_NODES; ++i)
old_b += cost_branch256(ct + 2 * i, oldplist[i]);
old_b += cost_branch256(ct + 2 * PIVOT_NODE, oldplist[PIVOT_NODE]);
bestsavings = 0;
bestnewp = oldp[PIVOT_NODE];
step = (*bestp > oldp[PIVOT_NODE] ? -1 : 1);
for (newp = *bestp; newp != oldp[PIVOT_NODE]; newp += step) {
if (newp < 1 || newp > 255)
continue;
newplist[PIVOT_NODE] = newp;
vp9_model_to_full_probs(newplist, newplist);
for (i = UNCONSTRAINED_NODES, new_b = 0; i < ENTROPY_NODES; ++i)
new_b += cost_branch256(ct + 2 * i, newplist[i]);
new_b += cost_branch256(ct + 2 * PIVOT_NODE, newplist[PIVOT_NODE]);
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update_b = prob_diff_update_cost(newp, oldp[PIVOT_NODE]) +
vp9_cost_upd256;
savings = old_b - new_b - update_b;
if (savings > bestsavings) {
bestsavings = savings;
bestnewp = newp;
}
}
*bestp = bestnewp;
return bestsavings;
}
void vp9_cond_prob_diff_update(vp9_writer *w, vp9_prob *oldp,
vp9_prob upd, unsigned int *ct) {
vp9_prob newp = get_binary_prob(ct[0], ct[1]);
const int savings = vp9_prob_diff_update_savings_search(ct, *oldp, &newp,
upd);
assert(newp >= 1);
if (savings > 0) {
vp9_write(w, 1, upd);
vp9_write_prob_diff_update(w, newp, *oldp);
*oldp = newp;
} else {
vp9_write(w, 0, upd);
}
}