mirror of
https://github.com/webmproject/libwebp.git
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230 lines
6.7 KiB
C
230 lines
6.7 KiB
C
// Copyright 2011 Google Inc. All Rights Reserved.
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//
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// This code is licensed under the same terms as WebM:
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// Software License Agreement: http://www.webmproject.org/license/software/
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// Additional IP Rights Grant: http://www.webmproject.org/license/additional/
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// -----------------------------------------------------------------------------
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//
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// Paginated token buffer
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//
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// A 'token' is a bit value associated with a probability, either fixed
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// or a later-to-be-determined after statistics have been collected.
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// For dynamic probability, we just record the slot id (idx) for the probability
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// value in the final probability array (uint8_t* probas in VP8EmitTokens).
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// Author: Skal (pascal.massimino@gmail.com)
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#include <assert.h>
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#include <stdlib.h>
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#include <string.h>
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#include "./vp8enci.h"
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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#define MAX_NUM_TOKEN 2048 // max number of token per page
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struct VP8Tokens {
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uint16_t tokens_[MAX_NUM_TOKEN]; // bit#15: bit
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// bit #14: constant proba or idx
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// bits 0..13: slot or constant proba
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VP8Tokens* next_;
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};
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void VP8TBufferInit(VP8TBuffer* const b) {
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b->tokens_ = NULL;
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b->pages_ = NULL;
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b->last_page_ = &b->pages_;
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b->left_ = 0;
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b->error_ = 0;
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}
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//------------------------------------------------------------------------------
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#ifdef USE_TOKEN_BUFFER
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void VP8TBufferClear(VP8TBuffer* const b) {
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if (b != NULL) {
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const VP8Tokens* p = b->rows_;
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while (p != NULL) {
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const VP8Tokens* const next = p->next_;
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free((void*)p);
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p = next;
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}
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VP8TBufferInit(b);
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}
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}
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static int TBufferNewPage(VP8TBuffer* const b) {
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VP8Tokens* const page = b->error_ ? NULL : (VP8Tokens*)malloc(sizeof(*page));
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if (page == NULL) {
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b->error_ = 1;
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return 0;
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}
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*b->last_page__ = page;
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b->last_page_ = &page->next_;
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b->left_ = MAX_NUM_TOKEN;
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b->tokens_ = page->tokens_;
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page->next_ = NULL;
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return 1;
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}
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//------------------------------------------------------------------------------
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#define TOKEN_ID(b, ctx, p) ((p) + NUM_PROBAS * ((ctx) + (b) * NUM_CTX))
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static WEBP_INLINE int VP8AddToken(VP8TBuffer* const b,
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int bit, int proba_idx) {
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assert(proba_idx < (1 << 14));
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if (b->left_ > 0 || TBufferNewPage(b)) {
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const int slot = --b->left_;
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b->tokens_[slot] = ((!bit) << 15) | proba_idx;
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}
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return bit;
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}
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static WEBP_INLINE void VP8AddConstantToken(VP8TBuffer* const b,
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int bit, int proba) {
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assert(proba < 256);
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if (b->left_ > 0 || TBufferNewPage(b)) {
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const int slot = --b->left_;
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b->tokens_[slot] = (bit << 15) | (1 << 14) | proba;
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}
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}
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int VP8RecordCoeffTokens(int ctx, int first, int last,
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const int16_t* const coeffs, VP8TBuffer* tokens) {
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int n = first;
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int b = VP8EncBands[n];
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if (!VP8AddToken(tokens, last >= 0, TOKEN_ID(b, ctx, 0))) {
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return 0;
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}
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while (n < 16) {
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const int c = coeffs[n++];
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const int sign = c < 0;
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int v = sign ? -c : c;
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const int base_id = TOKEN_ID(b, ctx, 0);
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if (!VP8AddToken(tokens, v != 0, base_id + 1)) {
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b = VP8EncBands[n];
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ctx = 0;
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continue;
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}
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if (!VP8AddToken(tokens, v > 1, base_id + 2)) {
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b = VP8EncBands[n];
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ctx = 1;
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} else {
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if (!VP8AddToken(tokens, v > 4, base_id + 3)) {
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if (VP8AddToken(tokens, v != 2, base_id + 4))
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VP8AddToken(tokens, v == 4, base_id + 5);
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} else if (!VP8AddToken(tokens, v > 10, base_id + 6)) {
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if (!VP8AddToken(tokens, v > 6, base_id + 7)) {
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VP8AddConstantToken(tokens, v == 6, 159);
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} else {
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VP8AddConstantToken(tokens, v >= 9, 165);
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VP8AddConstantToken(tokens, !(v & 1), 145);
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}
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} else {
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int mask;
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const uint8_t* tab;
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if (v < 3 + (8 << 1)) { // VP8Cat3 (3b)
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VP8AddToken(tokens, 0, base_id + 8);
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VP8AddToken(tokens, 0, base_id + 9);
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v -= 3 + (8 << 0);
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mask = 1 << 2;
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tab = VP8Cat3;
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} else if (v < 3 + (8 << 2)) { // VP8Cat4 (4b)
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VP8AddToken(tokens, 0, base_id + 8);
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VP8AddToken(tokens, 1, base_id + 9);
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v -= 3 + (8 << 1);
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mask = 1 << 3;
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tab = VP8Cat4;
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} else if (v < 3 + (8 << 3)) { // VP8Cat5 (5b)
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VP8AddToken(tokens, 1, base_id + 8);
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VP8AddToken(tokens, 0, base_id + 10);
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v -= 3 + (8 << 2);
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mask = 1 << 4;
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tab = VP8Cat5;
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} else { // VP8Cat6 (11b)
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VP8AddToken(tokens, 1, base_id + 8);
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VP8AddToken(tokens, 1, base_id + 10);
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v -= 3 + (8 << 3);
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mask = 1 << 10;
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tab = VP8Cat6;
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}
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while (mask) {
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VP8AddConstantToken(tokens, !!(v & mask), *tab++);
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mask >>= 1;
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}
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}
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ctx = 2;
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}
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b = VP8EncBands[n];
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VP8AddConstantToken(tokens, sign, 128);
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if (n == 16 || !VP8AddToken(tokens, n <= last, TOKEN_ID(b, ctx, 0))) {
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return 1; // EOB
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}
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}
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return 1;
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}
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#undef TOKEN_ID
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//------------------------------------------------------------------------------
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static void Record(int bit, proba_t* const stats) {
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proba_t p = *stats;
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if (p >= 0xffff0000u) { // an overflow is inbound.
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p = ((p + 1u) >> 1) & 0x7fff7fffu; // -> divide the stats by 2.
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}
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// record bit count (lower 16 bits) and increment total count (upper 16 bits).
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p += 0x00010000u + bit;
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*stats = p;
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}
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void VP8TokenToStats(const VP8TBuffer* const b, proba_t* const stats) {
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const VP8Tokens* p = b->rows_;
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while (p != NULL) {
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const int N = (p->next_ == NULL) ? b->left_ : 0;
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int n = MAX_NUM_TOKEN;
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while (n-- > N) {
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const uint16_t token = p->tokens_[n];
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if (!(token & (1 << 14))) {
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Record((token >> 15) & 1, stats + (token & 0x3fffu));
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}
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}
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p = p->next_;
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}
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}
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int VP8EmitTokens(const VP8TBuffer* const b, VP8BitWriter* const bw,
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const uint8_t* const probas, int final_pass) {
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const VP8Tokens* p = b->rows_;
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if (b->error_) return 0;
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while (p != NULL) {
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const VP8Tokens* const next = p->next_;
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const int N = (next == NULL) ? b->left_ : 0;
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int n = MAX_NUM_TOKEN;
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while (n-- > N) {
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const uint16_t token = p->tokens_[n];
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if (token & (1 << 14)) {
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VP8PutBit(bw, (token >> 15) & 1, token & 0x3fffu); // constant proba
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} else {
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VP8PutBit(bw, (token >> 15) & 1, probas[token & 0x3fffu]);
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}
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}
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p = next;
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}
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return 1;
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}
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//------------------------------------------------------------------------------
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#endif // USE_TOKEN_BUFFER
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#if defined(__cplusplus) || defined(c_plusplus)
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} // extern "C"
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#endif
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