token_enc.c 9.1 KB
Newer Older
wester committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294
// 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_enc.h"
#include "./vp8i_enc.h"
#include "../utils/utils.h"

#if !defined(DISABLE_TOKEN_BUFFER)

// we use pages to reduce the number of memcpy()
#define MIN_PAGE_SIZE 8192          // minimum number of token per page
#define FIXED_PROBA_BIT (1u << 14)

typedef uint16_t token_t;  // bit #15: bit value
                           // bit #14: flags for constant proba or idx
                           // bits #0..13: slot or constant proba
struct VP8Tokens {
  VP8Tokens* next_;        // pointer to next page
};
// Token data is located in memory just after the next_ field.
// This macro is used to return their address and hide the trick.
#define TOKEN_DATA(p) ((const token_t*)&(p)[1])

//------------------------------------------------------------------------------

void VP8TBufferInit(VP8TBuffer* const b, int page_size) {
  b->tokens_ = NULL;
  b->pages_ = NULL;
  b->last_page_ = &b->pages_;
  b->left_ = 0;
  b->page_size_ = (page_size < MIN_PAGE_SIZE) ? MIN_PAGE_SIZE : page_size;
  b->error_ = 0;
}

void VP8TBufferClear(VP8TBuffer* const b) {
  if (b != NULL) {
    VP8Tokens* p = b->pages_;
    while (p != NULL) {
      VP8Tokens* const next = p->next_;
      WebPSafeFree(p);
      p = next;
    }
    VP8TBufferInit(b, b->page_size_);
  }
}

static int TBufferNewPage(VP8TBuffer* const b) {
  VP8Tokens* page = NULL;
  if (!b->error_) {
    const size_t size = sizeof(*page) + b->page_size_ * sizeof(token_t);
    page = (VP8Tokens*)WebPSafeMalloc(1ULL, size);
  }
  if (page == NULL) {
    b->error_ = 1;
    return 0;
  }
  page->next_ = NULL;

  *b->last_page_ = page;
  b->last_page_ = &page->next_;
  b->left_ = b->page_size_;
  b->tokens_ = (token_t*)TOKEN_DATA(page);
  return 1;
}

//------------------------------------------------------------------------------

#define TOKEN_ID(t, b, ctx) \
    (NUM_PROBAS * ((ctx) + NUM_CTX * ((b) + NUM_BANDS * (t))))

static WEBP_INLINE uint32_t AddToken(VP8TBuffer* const b, uint32_t bit,
                                     uint32_t proba_idx,
                                     proba_t* const stats) {
  assert(proba_idx < FIXED_PROBA_BIT);
  assert(bit <= 1);
  if (b->left_ > 0 || TBufferNewPage(b)) {
    const int slot = --b->left_;
    b->tokens_[slot] = (bit << 15) | proba_idx;
  }
  VP8RecordStats(bit, stats);
  return bit;
}

static WEBP_INLINE void AddConstantToken(VP8TBuffer* const b,
                                         uint32_t bit, uint32_t proba) {
  assert(proba < 256);
  assert(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, const struct VP8Residual* const res,
                         VP8TBuffer* const tokens) {
  const int16_t* const coeffs = res->coeffs;
  const int coeff_type = res->coeff_type;
  const int last = res->last;
  int n = res->first;
  uint32_t base_id = TOKEN_ID(coeff_type, n, ctx);
  // should be stats[VP8EncBands[n]], but it's equivalent for n=0 or 1
  proba_t* s = res->stats[n][ctx];
  if (!AddToken(tokens, last >= 0, base_id + 0, s + 0)) {
    return 0;
  }

  while (n < 16) {
    const int c = coeffs[n++];
    const int sign = c < 0;
    const uint32_t v = sign ? -c : c;
    if (!AddToken(tokens, v != 0, base_id + 1, s + 1)) {
      base_id = TOKEN_ID(coeff_type, VP8EncBands[n], 0);  // ctx=0
      s = res->stats[VP8EncBands[n]][0];
      continue;
    }
    if (!AddToken(tokens, v > 1, base_id + 2, s + 2)) {
      base_id = TOKEN_ID(coeff_type, VP8EncBands[n], 1);  // ctx=1
      s = res->stats[VP8EncBands[n]][1];
    } else {
      if (!AddToken(tokens, v > 4, base_id + 3, s + 3)) {
        if (AddToken(tokens, v != 2, base_id + 4, s + 4)) {
          AddToken(tokens, v == 4, base_id + 5, s + 5);
        }
      } else if (!AddToken(tokens, v > 10, base_id + 6, s + 6)) {
        if (!AddToken(tokens, v > 6, base_id + 7, s + 7)) {
          AddConstantToken(tokens, v == 6, 159);
        } else {
          AddConstantToken(tokens, v >= 9, 165);
          AddConstantToken(tokens, !(v & 1), 145);
        }
      } else {
        int mask;
        const uint8_t* tab;
        uint32_t residue = v - 3;
        if (residue < (8 << 1)) {          // VP8Cat3  (3b)
          AddToken(tokens, 0, base_id + 8, s + 8);
          AddToken(tokens, 0, base_id + 9, s + 9);
          residue -= (8 << 0);
          mask = 1 << 2;
          tab = VP8Cat3;
        } else if (residue < (8 << 2)) {   // VP8Cat4  (4b)
          AddToken(tokens, 0, base_id + 8, s + 8);
          AddToken(tokens, 1, base_id + 9, s + 9);
          residue -= (8 << 1);
          mask = 1 << 3;
          tab = VP8Cat4;
        } else if (residue < (8 << 3)) {   // VP8Cat5  (5b)
          AddToken(tokens, 1, base_id + 8, s + 8);
          AddToken(tokens, 0, base_id + 10, s + 9);
          residue -= (8 << 2);
          mask = 1 << 4;
          tab = VP8Cat5;
        } else {                         // VP8Cat6 (11b)
          AddToken(tokens, 1, base_id + 8, s + 8);
          AddToken(tokens, 1, base_id + 10, s + 9);
          residue -= (8 << 3);
          mask = 1 << 10;
          tab = VP8Cat6;
        }
        while (mask) {
          AddConstantToken(tokens, !!(residue & mask), *tab++);
          mask >>= 1;
        }
      }
      base_id = TOKEN_ID(coeff_type, VP8EncBands[n], 2);  // ctx=2
      s = res->stats[VP8EncBands[n]][2];
    }
    AddConstantToken(tokens, sign, 128);
    if (n == 16 || !AddToken(tokens, n <= last, base_id + 0, s + 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;
    const token_t* const tokens = TOKEN_DATA(p);
    while (n-- > N) {
      const token_t token = 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_;
  assert(!b->error_);
  while (p != NULL) {
    const VP8Tokens* const next = p->next_;
    const int N = (next == NULL) ? b->left_ : 0;
    int n = b->page_size_;
    const token_t* const tokens = TOKEN_DATA(p);
    while (n-- > N) {
      const token_t token = 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) WebPSafeFree((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_;
  assert(!b->error_);
  while (p != NULL) {
    const VP8Tokens* const next = p->next_;
    const int N = (next == NULL) ? b->left_ : 0;
    int n = b->page_size_;
    const token_t* const tokens = TOKEN_DATA(p);
    while (n-- > N) {
      const token_t token = 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