vp8/encoder/boolhuff.c

/*
 *  Copyright (c) 2010 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 "boolhuff.h"

#if defined(SECTIONBITS_OUTPUT)
unsigned __int64 Sectionbits[500];

#endif

#ifdef ENTROPY_STATS
unsigned int active_section = 0;
#endif

const unsigned int vp9_prob_cost[256] = {
  2047, 2047, 1791, 1641, 1535, 1452, 1385, 1328, 1279, 1235, 1196, 1161, 1129, 1099, 1072, 1046,
  1023, 1000,  979,  959,  940,  922,  905,  889,  873,  858,  843,  829,  816,  803,  790,  778,
  767,  755,  744,  733,  723,  713,  703,  693,  684,  675,  666,  657,  649,  641,  633,  625,
  617,  609,  602,  594,  587,  580,  573,  567,  560,  553,  547,  541,  534,  528,  522,  516,
  511,  505,  499,  494,  488,  483,  477,  472,  467,  462,  457,  452,  447,  442,  437,  433,
  428,  424,  419,  415,  410,  406,  401,  397,  393,  389,  385,  381,  377,  373,  369,  365,
  361,  357,  353,  349,  346,  342,  338,  335,  331,  328,  324,  321,  317,  314,  311,  307,
  304,  301,  297,  294,  291,  288,  285,  281,  278,  275,  272,  269,  266,  263,  260,  257,
  255,  252,  249,  246,  243,  240,  238,  235,  232,  229,  227,  224,  221,  219,  216,  214,
  211,  208,  206,  203,  201,  198,  196,  194,  191,  189,  186,  184,  181,  179,  177,  174,
  172,  170,  168,  165,  163,  161,  159,  156,  154,  152,  150,  148,  145,  143,  141,  139,
  137,  135,  133,  131,  129,  127,  125,  123,  121,  119,  117,  115,  113,  111,  109,  107,
  105,  103,  101,   99,   97,   95,   93,   92,   90,   88,   86,   84,   82,   81,   79,   77,
  75,   73,   72,   70,   68,   66,   65,   63,   61,   60,   58,   56,   55,   53,   51,   50,
  48,   46,   45,   43,   41,   40,   38,   37,   35,   33,   32,   30,   29,   27,   25,   24,
  22,   21,   19,   18,   16,   15,   13,   12,   10,    9,    7,    6,    4,    3,    1,   1
};

void vp9_start_encode(BOOL_CODER *br, unsigned char *source) {

  br->lowvalue = 0;
  br->range    = 255;
  br->value    = 0;
  br->count    = -24;
  br->buffer   = source;
  br->pos      = 0;
}

void vp9_stop_encode(BOOL_CODER *br) {
  int i;

  for (i = 0; i < 32; i++)
    encode_bool(br, 0, 128);
}


void vp9_encode_value(BOOL_CODER *br, int data, int bits) {
  int bit;

  for (bit = bits - 1; bit >= 0; bit--)
    encode_bool(br, (1 & (data >> bit)), 0x80);
}

int vp9_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 get_unsigned_bits(unsigned num_values) {
  int cat = 0;
  if ((num_values--) <= 1) return 0;
  while (num_values > 0) {
    cat++;
    num_values >>= 1;
  }
  return cat;
}

void vp9_encode_uniform(BOOL_CODER *br, int v, int n) {
  int l = get_unsigned_bits(n);
  int m;
  if (l == 0) return;
  m = (1 << l) - n;
  if (v < m)
    vp9_encode_value(br, v, l - 1);
  else {
    vp9_encode_value(br, m + ((v - m) >> 1), l - 1);
    vp9_encode_value(br, (v - m) & 1, 1);
  }
}

int vp9_count_uniform(int v, int n) {
  int l = get_unsigned_bits(n);
  int m;
  if (l == 0) return 0;
  m = (1 << l) - n;
  if (v < m)
    return l - 1;
  else
    return l;
}

void vp9_encode_term_subexp(BOOL_CODER *br, int word, int k, int num_syms) {
  int i = 0;
  int mk = 0;
  while (1) {
    int b = (i ? k + i - 1 : k);
    int a = (1 << b);
    if (num_syms <= mk + 3 * a) {
      vp9_encode_uniform(br, word - mk, num_syms - mk);
      break;
    } else {
      int t = (word >= mk + a);
      vp9_encode_value(br, t, 1);
      if (t) {
        i = i + 1;
        mk += a;
      } else {
        vp9_encode_value(br, word - mk, b);
        break;
      }
    }
  }
}

int vp9_count_term_subexp(int word, int k, int num_syms) {
  int count = 0;
  int i = 0;
  int mk = 0;
  while (1) {
    int b = (i ? k + i - 1 : k);
    int a = (1 << b);
    if (num_syms <= mk + 3 * a) {
      count += vp9_count_uniform(word - mk, num_syms - mk);
      break;
    } else {
      int t = (word >= mk + a);
      count++;
      if (t) {
        i = i + 1;
        mk += a;
      } else {
        count += b;
        break;
      }
    }
  }
  return count;
}