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token_enc.c (8486B)

      1 // Copyright 2011 Google Inc. All Rights Reserved.
      2 //
      3 // Use of this source code is governed by a BSD-style license
      4 // that can be found in the COPYING file in the root of the source
      5 // tree. An additional intellectual property rights grant can be found
      6 // in the file PATENTS. All contributing project authors may
      7 // be found in the AUTHORS file in the root of the source tree.
      8 // -----------------------------------------------------------------------------
      9 //
     10 // Paginated token buffer
     11 //
     12 //  A 'token' is a bit value associated with a probability, either fixed
     13 // or a later-to-be-determined after statistics have been collected.
     14 // For dynamic probability, we just record the slot id (idx) for the probability
     15 // value in the final probability array (uint8_t* probas in VP8EmitTokens).
     16 //
     17 // Author: Skal (pascal.massimino@gmail.com)
     18 
     19 #include <assert.h>
     20 #include <stdlib.h>
     21 #include <string.h>
     22 
     23 #include "src/dec/common_dec.h"
     24 #include "src/dsp/dsp.h"
     25 #include "src/enc/cost_enc.h"
     26 #include "src/enc/vp8i_enc.h"
     27 #include "src/utils/bit_writer_utils.h"
     28 #include "src/utils/utils.h"
     29 #include "src/webp/types.h"
     30 
     31 #if !defined(DISABLE_TOKEN_BUFFER)
     32 
     33 // we use pages to reduce the number of memcpy()
     34 #define MIN_PAGE_SIZE 8192          // minimum number of token per page
     35 #define FIXED_PROBA_BIT (1u << 14)
     36 
     37 typedef uint16_t token_t;  // bit #15: bit value
     38                            // bit #14: flags for constant proba or idx
     39                            // bits #0..13: slot or constant proba
     40 struct VP8Tokens {
     41   VP8Tokens* next;         // pointer to next page
     42 };
     43 // Token data is located in memory just after the 'next' field.
     44 // This macro is used to return their address and hide the trick.
     45 #define TOKEN_DATA(p) ((const token_t*)&(p)[1])
     46 
     47 //------------------------------------------------------------------------------
     48 
     49 void VP8TBufferInit(VP8TBuffer* const b, int page_size) {
     50   b->tokens = NULL;
     51   b->pages = NULL;
     52   b->last_page = &b->pages;
     53   b->left = 0;
     54   b->page_size = (page_size < MIN_PAGE_SIZE) ? MIN_PAGE_SIZE : page_size;
     55   b->error = 0;
     56 }
     57 
     58 void VP8TBufferClear(VP8TBuffer* const b) {
     59   if (b != NULL) {
     60     VP8Tokens* p = b->pages;
     61     while (p != NULL) {
     62       VP8Tokens* const next = p->next;
     63       WebPSafeFree(p);
     64       p = next;
     65     }
     66     VP8TBufferInit(b, b->page_size);
     67   }
     68 }
     69 
     70 static int TBufferNewPage(VP8TBuffer* const b) {
     71   VP8Tokens* page = NULL;
     72   if (!b->error) {
     73     const size_t size = sizeof(*page) + b->page_size * sizeof(token_t);
     74     page = (VP8Tokens*)WebPSafeMalloc(1ULL, size);
     75   }
     76   if (page == NULL) {
     77     b->error = 1;
     78     return 0;
     79   }
     80   page->next = NULL;
     81 
     82   *b->last_page = page;
     83   b->last_page = &page->next;
     84   b->left = b->page_size;
     85   b->tokens = (token_t*)TOKEN_DATA(page);
     86   return 1;
     87 }
     88 
     89 //------------------------------------------------------------------------------
     90 
     91 #define TOKEN_ID(t, b, ctx) \
     92     (NUM_PROBAS * ((ctx) + NUM_CTX * ((b) + NUM_BANDS * (t))))
     93 
     94 static WEBP_INLINE uint32_t AddToken(VP8TBuffer* const b, uint32_t bit,
     95                                      uint32_t proba_idx,
     96                                      proba_t* const stats) {
     97   assert(proba_idx < FIXED_PROBA_BIT);
     98   assert(bit <= 1);
     99   if (b->left > 0 || TBufferNewPage(b)) {
    100     const int slot = --b->left;
    101     b->tokens[slot] = (bit << 15) | proba_idx;
    102   }
    103   VP8RecordStats(bit, stats);
    104   return bit;
    105 }
    106 
    107 static WEBP_INLINE void AddConstantToken(VP8TBuffer* const b,
    108                                          uint32_t bit, uint32_t proba) {
    109   assert(proba < 256);
    110   assert(bit <= 1);
    111   if (b->left > 0 || TBufferNewPage(b)) {
    112     const int slot = --b->left;
    113     b->tokens[slot] = (bit << 15) | FIXED_PROBA_BIT | proba;
    114   }
    115 }
    116 
    117 int VP8RecordCoeffTokens(int ctx, const struct VP8Residual* const res,
    118                          VP8TBuffer* const tokens) {
    119   const int16_t* const coeffs = res->coeffs;
    120   const int coeff_type = res->coeff_type;
    121   const int last = res->last;
    122   int n = res->first;
    123   uint32_t base_id = TOKEN_ID(coeff_type, n, ctx);
    124   // should be stats[VP8EncBands[n]], but it's equivalent for n=0 or 1
    125   proba_t* s = res->stats[n][ctx];
    126   if (!AddToken(tokens, last >= 0, base_id + 0, s + 0)) {
    127     return 0;
    128   }
    129 
    130   while (n < 16) {
    131     const int c = coeffs[n++];
    132     const int sign = c < 0;
    133     const uint32_t v = sign ? -c : c;
    134     if (!AddToken(tokens, v != 0, base_id + 1, s + 1)) {
    135       base_id = TOKEN_ID(coeff_type, VP8EncBands[n], 0);  // ctx=0
    136       s = res->stats[VP8EncBands[n]][0];
    137       continue;
    138     }
    139     if (!AddToken(tokens, v > 1, base_id + 2, s + 2)) {
    140       base_id = TOKEN_ID(coeff_type, VP8EncBands[n], 1);  // ctx=1
    141       s = res->stats[VP8EncBands[n]][1];
    142     } else {
    143       if (!AddToken(tokens, v > 4, base_id + 3, s + 3)) {
    144         if (AddToken(tokens, v != 2, base_id + 4, s + 4)) {
    145           AddToken(tokens, v == 4, base_id + 5, s + 5);
    146         }
    147       } else if (!AddToken(tokens, v > 10, base_id + 6, s + 6)) {
    148         if (!AddToken(tokens, v > 6, base_id + 7, s + 7)) {
    149           AddConstantToken(tokens, v == 6, 159);
    150         } else {
    151           AddConstantToken(tokens, v >= 9, 165);
    152           AddConstantToken(tokens, !(v & 1), 145);
    153         }
    154       } else {
    155         int mask;
    156         const uint8_t* tab;
    157         uint32_t residue = v - 3;
    158         if (residue < (8 << 1)) {          // VP8Cat3  (3b)
    159           AddToken(tokens, 0, base_id + 8, s + 8);
    160           AddToken(tokens, 0, base_id + 9, s + 9);
    161           residue -= (8 << 0);
    162           mask = 1 << 2;
    163           tab = VP8Cat3;
    164         } else if (residue < (8 << 2)) {   // VP8Cat4  (4b)
    165           AddToken(tokens, 0, base_id + 8, s + 8);
    166           AddToken(tokens, 1, base_id + 9, s + 9);
    167           residue -= (8 << 1);
    168           mask = 1 << 3;
    169           tab = VP8Cat4;
    170         } else if (residue < (8 << 3)) {   // VP8Cat5  (5b)
    171           AddToken(tokens, 1, base_id + 8, s + 8);
    172           AddToken(tokens, 0, base_id + 10, s + 9);
    173           residue -= (8 << 2);
    174           mask = 1 << 4;
    175           tab = VP8Cat5;
    176         } else {                         // VP8Cat6 (11b)
    177           AddToken(tokens, 1, base_id + 8, s + 8);
    178           AddToken(tokens, 1, base_id + 10, s + 9);
    179           residue -= (8 << 3);
    180           mask = 1 << 10;
    181           tab = VP8Cat6;
    182         }
    183         while (mask) {
    184           AddConstantToken(tokens, !!(residue & mask), *tab++);
    185           mask >>= 1;
    186         }
    187       }
    188       base_id = TOKEN_ID(coeff_type, VP8EncBands[n], 2);  // ctx=2
    189       s = res->stats[VP8EncBands[n]][2];
    190     }
    191     AddConstantToken(tokens, sign, 128);
    192     if (n == 16 || !AddToken(tokens, n <= last, base_id + 0, s + 0)) {
    193       return 1;   // EOB
    194     }
    195   }
    196   return 1;
    197 }
    198 
    199 #undef TOKEN_ID
    200 
    201 //------------------------------------------------------------------------------
    202 // Final coding pass, with known probabilities
    203 
    204 int VP8EmitTokens(VP8TBuffer* const b, VP8BitWriter* const bw,
    205                   const uint8_t* const probas, int final_pass) {
    206   const VP8Tokens* p = b->pages;
    207   assert(!b->error);
    208   while (p != NULL) {
    209     const VP8Tokens* const next = p->next;
    210     const int N = (next == NULL) ? b->left : 0;
    211     int n = b->page_size;
    212     const token_t* const tokens = TOKEN_DATA(p);
    213     while (n-- > N) {
    214       const token_t token = tokens[n];
    215       const int bit = (token >> 15) & 1;
    216       if (token & FIXED_PROBA_BIT) {
    217         VP8PutBit(bw, bit, token & 0xffu);  // constant proba
    218       } else {
    219         VP8PutBit(bw, bit, probas[token & 0x3fffu]);
    220       }
    221     }
    222     if (final_pass) WebPSafeFree((void*)p);
    223     p = next;
    224   }
    225   if (final_pass) b->pages = NULL;
    226   return 1;
    227 }
    228 
    229 // Size estimation
    230 size_t VP8EstimateTokenSize(VP8TBuffer* const b, const uint8_t* const probas) {
    231   size_t size = 0;
    232   const VP8Tokens* p = b->pages;
    233   assert(!b->error);
    234   while (p != NULL) {
    235     const VP8Tokens* const next = p->next;
    236     const int N = (next == NULL) ? b->left : 0;
    237     int n = b->page_size;
    238     const token_t* const tokens = TOKEN_DATA(p);
    239     while (n-- > N) {
    240       const token_t token = tokens[n];
    241       const int bit = token & (1 << 15);
    242       if (token & FIXED_PROBA_BIT) {
    243         size += VP8BitCost(bit, token & 0xffu);
    244       } else {
    245         size += VP8BitCost(bit, probas[token & 0x3fffu]);
    246       }
    247     }
    248     p = next;
    249   }
    250   return size;
    251 }
    252 
    253 //------------------------------------------------------------------------------
    254 
    255 #else     // DISABLE_TOKEN_BUFFER
    256 
    257 void VP8TBufferInit(VP8TBuffer* const b, int page_size) {
    258   (void)b;
    259   (void)page_size;
    260 }
    261 void VP8TBufferClear(VP8TBuffer* const b) {
    262   (void)b;
    263 }
    264 
    265 #endif    // !DISABLE_TOKEN_BUFFER