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// Copyright 2011 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING 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.
// -----------------------------------------------------------------------------
//
// Paginated token buffer
//
// A 'token' is a bit value associated with a probability, either fixed
// or a later-to-be-determined after statistics have been collected.
// For dynamic probability, we just record the slot id (idx) for the probability
// value in the final probability array (uint8_t* probas in VP8EmitTokens).
//
// Author: Skal (pascal.massimino@gmail.com)
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include "./cost.h"
#include "./vp8enci.h"
#if !defined(DISABLE_TOKEN_BUFFER)
// we use pages to reduce the number of memcpy()
#define MAX_NUM_TOKEN 8192 // max number of token per page
#define FIXED_PROBA_BIT (1u << 14)
struct VP8Tokens {
uint16_t tokens_[MAX_NUM_TOKEN]; // bit#15: bit
// bit #14: constant proba or idx
// bits 0..13: slot or constant proba
VP8Tokens* next_;
};
//------------------------------------------------------------------------------
void VP8TBufferInit(VP8TBuffer* const b) {
b->tokens_ = NULL;
b->pages_ = NULL;
b->last_page_ = &b->pages_;
b->left_ = 0;
b->error_ = 0;
}
void VP8TBufferClear(VP8TBuffer* const b) {
if (b != NULL) {
const VP8Tokens* p = b->pages_;
while (p != NULL) {
const VP8Tokens* const next = p->next_;
free((void*)p);
p = next;
}
VP8TBufferInit(b);
}
}
static int TBufferNewPage(VP8TBuffer* const b) {
VP8Tokens* const page = b->error_ ? NULL : (VP8Tokens*)malloc(sizeof(*page));
if (page == NULL) {
b->error_ = 1;
return 0;
}
*b->last_page_ = page;
b->last_page_ = &page->next_;
b->left_ = MAX_NUM_TOKEN;
b->tokens_ = page->tokens_;
page->next_ = NULL;
return 1;
}
//------------------------------------------------------------------------------
#define TOKEN_ID(t, b, ctx, p) \
((p) + NUM_PROBAS * ((ctx) + NUM_CTX * ((b) + NUM_BANDS * (t))))
static WEBP_INLINE int AddToken(VP8TBuffer* const b,
int bit, uint32_t proba_idx) {
assert(proba_idx < FIXED_PROBA_BIT);
assert(bit == 0 || bit == 1);
if (b->left_ > 0 || TBufferNewPage(b)) {
const int slot = --b->left_;
b->tokens_[slot] = (bit << 15) | proba_idx;
}
return bit;
}
static WEBP_INLINE void AddConstantToken(VP8TBuffer* const b,
int bit, int proba) {
assert(proba < 256);
assert(bit == 0 || bit == 1);
if (b->left_ > 0 || TBufferNewPage(b)) {
const int slot = --b->left_;
b->tokens_[slot] = (bit << 15) | FIXED_PROBA_BIT | proba;
}
}
int VP8RecordCoeffTokens(int ctx, int coeff_type, int first, int last,
const int16_t* const coeffs,
VP8TBuffer* const tokens) {
int n = first;
uint32_t base_id = TOKEN_ID(coeff_type, n, ctx, 0);
if (!AddToken(tokens, last >= 0, base_id + 0)) {
return 0;
}
while (n < 16) {
const int c = coeffs[n++];
const int sign = c < 0;
int v = sign ? -c : c;
if (!AddToken(tokens, v != 0, base_id + 1)) {
ctx = 0;
base_id = TOKEN_ID(coeff_type, VP8EncBands[n], ctx, 0);
continue;
}
if (!AddToken(tokens, v > 1, base_id + 2)) {
ctx = 1;
} else {
if (!AddToken(tokens, v > 4, base_id + 3)) {
if (AddToken(tokens, v != 2, base_id + 4))
AddToken(tokens, v == 4, base_id + 5);
} else if (!AddToken(tokens, v > 10, base_id + 6)) {
if (!AddToken(tokens, v > 6, base_id + 7)) {
AddConstantToken(tokens, v == 6, 159);
} else {
AddConstantToken(tokens, v >= 9, 165);
AddConstantToken(tokens, !(v & 1), 145);
}
} else {
int mask;
const uint8_t* tab;
if (v < 3 + (8 << 1)) { // VP8Cat3 (3b)
AddToken(tokens, 0, base_id + 8);
AddToken(tokens, 0, base_id + 9);
v -= 3 + (8 << 0);
mask = 1 << 2;
tab = VP8Cat3;
} else if (v < 3 + (8 << 2)) { // VP8Cat4 (4b)
AddToken(tokens, 0, base_id + 8);
AddToken(tokens, 1, base_id + 9);
v -= 3 + (8 << 1);
mask = 1 << 3;
tab = VP8Cat4;
} else if (v < 3 + (8 << 3)) { // VP8Cat5 (5b)
AddToken(tokens, 1, base_id + 8);
AddToken(tokens, 0, base_id + 10);
v -= 3 + (8 << 2);
mask = 1 << 4;
tab = VP8Cat5;
} else { // VP8Cat6 (11b)
AddToken(tokens, 1, base_id + 8);
AddToken(tokens, 1, base_id + 10);
v -= 3 + (8 << 3);
mask = 1 << 10;
tab = VP8Cat6;
}
while (mask) {
AddConstantToken(tokens, !!(v & mask), *tab++);
mask >>= 1;
}
}
ctx = 2;
}
AddConstantToken(tokens, sign, 128);
base_id = TOKEN_ID(coeff_type, VP8EncBands[n], ctx, 0);
if (n == 16 || !AddToken(tokens, n <= last, base_id + 0)) {
return 1; // EOB
}
}
return 1;
}
#undef TOKEN_ID
//------------------------------------------------------------------------------
// This function works, but isn't currently used. Saved for later.
#if 0
static void Record(int bit, proba_t* const stats) {
proba_t p = *stats;
if (p >= 0xffff0000u) { // an overflow is inbound.
p = ((p + 1u) >> 1) & 0x7fff7fffu; // -> divide the stats by 2.
}
// record bit count (lower 16 bits) and increment total count (upper 16 bits).
p += 0x00010000u + bit;
*stats = p;
}
void VP8TokenToStats(const VP8TBuffer* const b, proba_t* const stats) {
const VP8Tokens* p = b->pages_;
while (p != NULL) {
const int N = (p->next_ == NULL) ? b->left_ : 0;
int n = MAX_NUM_TOKEN;
while (n-- > N) {
const uint16_t token = p->tokens_[n];
if (!(token & FIXED_PROBA_BIT)) {
Record((token >> 15) & 1, stats + (token & 0x3fffu));
}
}
p = p->next_;
}
}
#endif // 0
//------------------------------------------------------------------------------
// Final coding pass, with known probabilities
int VP8EmitTokens(VP8TBuffer* const b, VP8BitWriter* const bw,
const uint8_t* const probas, int final_pass) {
const VP8Tokens* p = b->pages_;
(void)final_pass;
if (b->error_) return 0;
while (p != NULL) {
const VP8Tokens* const next = p->next_;
const int N = (next == NULL) ? b->left_ : 0;
int n = MAX_NUM_TOKEN;
while (n-- > N) {
const uint16_t token = p->tokens_[n];
const int bit = (token >> 15) & 1;
if (token & FIXED_PROBA_BIT) {
VP8PutBit(bw, bit, token & 0xffu); // constant proba
} else {
VP8PutBit(bw, bit, probas[token & 0x3fffu]);
}
}
if (final_pass) free((void*)p);
p = next;
}
if (final_pass) b->pages_ = NULL;
return 1;
}
// Size estimation
size_t VP8EstimateTokenSize(VP8TBuffer* const b, const uint8_t* const probas) {
size_t size = 0;
const VP8Tokens* p = b->pages_;
if (b->error_) return 0;
while (p != NULL) {
const VP8Tokens* const next = p->next_;
const int N = (next == NULL) ? b->left_ : 0;
int n = MAX_NUM_TOKEN;
while (n-- > N) {
const uint16_t token = p->tokens_[n];
const int bit = token & (1 << 15);
if (token & FIXED_PROBA_BIT) {
size += VP8BitCost(bit, token & 0xffu);
} else {
size += VP8BitCost(bit, probas[token & 0x3fffu]);
}
}
p = next;
}
return size;
}
//------------------------------------------------------------------------------
#else // DISABLE_TOKEN_BUFFER
void VP8TBufferInit(VP8TBuffer* const b) {
(void)b;
}
void VP8TBufferClear(VP8TBuffer* const b) {
(void)b;
}
#endif // !DISABLE_TOKEN_BUFFER
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