ref: 7593588eb1c7e786b62c5f21c081a4bfb1d00d4f
dir: /vp9/encoder/vp9_subexp.c/
/*
* 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 "vpx_dsp/bitwriter.h"
#include "vp9/common/vp9_common.h"
#include "vp9/common/vp9_entropy.h"
#include "vp9/encoder/vp9_cost.h"
#include "vp9/encoder/vp9_subexp.h"
static const uint8_t update_bits[255] = {
5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11,
11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
11, 11, 11, 11, 11, 11, 11, 0,
};
#define MIN_DELP_BITS 5
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 const uint8_t 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,
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 prob_diff_update_cost(vpx_prob newp, vpx_prob oldp) {
int delp = remap_prob(newp, oldp);
return update_bits[delp] << VP9_PROB_COST_SHIFT;
}
static void encode_uniform(vpx_writer *w, int v) {
const int l = 8;
const int m = (1 << l) - 191;
if (v < m) {
vpx_write_literal(w, v, l - 1);
} else {
vpx_write_literal(w, m + ((v - m) >> 1), l - 1);
vpx_write_literal(w, (v - m) & 1, 1);
}
}
static INLINE int write_bit_gte(vpx_writer *w, int word, int test) {
vpx_write_literal(w, word >= test, 1);
return word >= test;
}
static void encode_term_subexp(vpx_writer *w, int word) {
if (!write_bit_gte(w, word, 16)) {
vpx_write_literal(w, word, 4);
} else if (!write_bit_gte(w, word, 32)) {
vpx_write_literal(w, word - 16, 4);
} else if (!write_bit_gte(w, word, 64)) {
vpx_write_literal(w, word - 32, 5);
} else {
encode_uniform(w, word - 64);
}
}
void vp9_write_prob_diff_update(vpx_writer *w, vpx_prob newp, vpx_prob oldp) {
const int delp = remap_prob(newp, oldp);
encode_term_subexp(w, delp);
}
int vp9_prob_diff_update_savings_search(const unsigned int *ct, vpx_prob oldp,
vpx_prob *bestp, vpx_prob upd) {
const int old_b = cost_branch256(ct, oldp);
int bestsavings = 0;
vpx_prob newp, bestnewp = oldp;
const int step = *bestp > oldp ? -1 : 1;
const int upd_cost = vp9_cost_one(upd) - vp9_cost_zero(upd);
if (old_b > upd_cost + (MIN_DELP_BITS << VP9_PROB_COST_SHIFT)) {
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) + upd_cost;
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 vpx_prob oldp,
vpx_prob *bestp, vpx_prob upd,
int stepsize) {
int i, old_b, new_b, update_b, savings, bestsavings;
int newp;
const int step_sign = *bestp > oldp ? -1 : 1;
const int step = stepsize * step_sign;
const int upd_cost = vp9_cost_one(upd) - vp9_cost_zero(upd);
const vpx_prob *newplist, *oldplist;
vpx_prob bestnewp;
oldplist = vp9_pareto8_full[oldp - 1];
old_b = cost_branch256(ct + 2 * PIVOT_NODE, oldp);
for (i = UNCONSTRAINED_NODES; i < ENTROPY_NODES; ++i)
old_b += cost_branch256(ct + 2 * i, oldplist[i - UNCONSTRAINED_NODES]);
bestsavings = 0;
bestnewp = oldp;
assert(stepsize > 0);
if (old_b > upd_cost + (MIN_DELP_BITS << VP9_PROB_COST_SHIFT)) {
for (newp = *bestp; (newp - oldp) * step_sign < 0; newp += step) {
if (newp < 1 || newp > 255) continue;
newplist = vp9_pareto8_full[newp - 1];
new_b = cost_branch256(ct + 2 * PIVOT_NODE, newp);
for (i = UNCONSTRAINED_NODES; i < ENTROPY_NODES; ++i)
new_b += cost_branch256(ct + 2 * i, newplist[i - UNCONSTRAINED_NODES]);
update_b = prob_diff_update_cost(newp, oldp) + upd_cost;
savings = old_b - new_b - update_b;
if (savings > bestsavings) {
bestsavings = savings;
bestnewp = newp;
}
}
}
*bestp = bestnewp;
return bestsavings;
}
void vp9_cond_prob_diff_update(vpx_writer *w, vpx_prob *oldp,
const unsigned int ct[2]) {
const vpx_prob upd = DIFF_UPDATE_PROB;
vpx_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) {
vpx_write(w, 1, upd);
vp9_write_prob_diff_update(w, newp, *oldp);
*oldp = newp;
} else {
vpx_write(w, 0, upd);
}
}