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  1. /*
  2.  * Copyright (C) 2007 Marco Gerards <marco@gnu.org>
  3.  * Copyright (C) 2009 David Conrad
  4.  *
  5.  * This file is part of FFmpeg.
  6.  *
  7.  * FFmpeg is free software; you can redistribute it and/or
  8.  * modify it under the terms of the GNU Lesser General Public
  9.  * License as published by the Free Software Foundation; either
  10.  * version 2.1 of the License, or (at your option) any later version.
  11.  *
  12.  * FFmpeg is distributed in the hope that it will be useful,
  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15.  * Lesser General Public License for more details.
  16.  *
  17.  * You should have received a copy of the GNU Lesser General Public
  18.  * License along with FFmpeg; if not, write to the Free Software
  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20.  */
  21.  
  22. /**
  23.  * @file
  24.  * Arithmetic decoder for Dirac
  25.  * @author Marco Gerards <marco@gnu.org>
  26.  */
  27.  
  28. #include "dirac_arith.h"
  29.  
  30.  
  31. const uint16_t ff_dirac_prob[256] = {
  32.     0,    2,    5,    8,    11,   15,   20,   24,
  33.     29,   35,   41,   47,   53,   60,   67,   74,
  34.     82,   89,   97,   106,  114,  123,  132,  141,
  35.     150,  160,  170,  180,  190,  201,  211,  222,
  36.     233,  244,  256,  267,  279,  291,  303,  315,
  37.     327,  340,  353,  366,  379,  392,  405,  419,
  38.     433,  447,  461,  475,  489,  504,  518,  533,
  39.     548,  563,  578,  593,  609,  624,  640,  656,
  40.     672,  688,  705,  721,  738,  754,  771,  788,
  41.     805,  822,  840,  857,  875,  892,  910,  928,
  42.     946,  964,  983,  1001, 1020, 1038, 1057, 1076,
  43.     1095, 1114, 1133, 1153, 1172, 1192, 1211, 1231,
  44.     1251, 1271, 1291, 1311, 1332, 1352, 1373, 1393,
  45.     1414, 1435, 1456, 1477, 1498, 1520, 1541, 1562,
  46.     1584, 1606, 1628, 1649, 1671, 1694, 1716, 1738,
  47.     1760, 1783, 1806, 1828, 1851, 1874, 1897, 1920,
  48.     1935, 1942, 1949, 1955, 1961, 1968, 1974, 1980,
  49.     1985, 1991, 1996, 2001, 2006, 2011, 2016, 2021,
  50.     2025, 2029, 2033, 2037, 2040, 2044, 2047, 2050,
  51.     2053, 2056, 2058, 2061, 2063, 2065, 2066, 2068,
  52.     2069, 2070, 2071, 2072, 2072, 2072, 2072, 2072,
  53.     2072, 2071, 2070, 2069, 2068, 2066, 2065, 2063,
  54.     2060, 2058, 2055, 2052, 2049, 2045, 2042, 2038,
  55.     2033, 2029, 2024, 2019, 2013, 2008, 2002, 1996,
  56.     1989, 1982, 1975, 1968, 1960, 1952, 1943, 1934,
  57.     1925, 1916, 1906, 1896, 1885, 1874, 1863, 1851,
  58.     1839, 1827, 1814, 1800, 1786, 1772, 1757, 1742,
  59.     1727, 1710, 1694, 1676, 1659, 1640, 1622, 1602,
  60.     1582, 1561, 1540, 1518, 1495, 1471, 1447, 1422,
  61.     1396, 1369, 1341, 1312, 1282, 1251, 1219, 1186,
  62.     1151, 1114, 1077, 1037, 995,  952,  906,  857,
  63.     805,  750,  690,  625,  553,  471,  376,  255
  64. };
  65.  
  66. const uint8_t ff_dirac_next_ctx[DIRAC_CTX_COUNT] = {
  67.     [CTX_ZPZN_F1]   = CTX_ZP_F2,
  68.     [CTX_ZPNN_F1]   = CTX_ZP_F2,
  69.     [CTX_ZP_F2]     = CTX_ZP_F3,
  70.     [CTX_ZP_F3]     = CTX_ZP_F4,
  71.     [CTX_ZP_F4]     = CTX_ZP_F5,
  72.     [CTX_ZP_F5]     = CTX_ZP_F6,
  73.     [CTX_ZP_F6]     = CTX_ZP_F6,
  74.     [CTX_NPZN_F1]   = CTX_NP_F2,
  75.     [CTX_NPNN_F1]   = CTX_NP_F2,
  76.     [CTX_NP_F2]     = CTX_NP_F3,
  77.     [CTX_NP_F3]     = CTX_NP_F4,
  78.     [CTX_NP_F4]     = CTX_NP_F5,
  79.     [CTX_NP_F5]     = CTX_NP_F6,
  80.     [CTX_NP_F6]     = CTX_NP_F6,
  81.     [CTX_DELTA_Q_F] = CTX_DELTA_Q_F,
  82. };
  83.  
  84. int16_t ff_dirac_prob_branchless[256][2];
  85.  
  86. void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int length)
  87. {
  88.     int i;
  89.     align_get_bits(gb);
  90.  
  91.     length = FFMIN(length, get_bits_left(gb)/8);
  92.  
  93.     c->bytestream     = gb->buffer + get_bits_count(gb)/8;
  94.     c->bytestream_end = c->bytestream + length;
  95.     skip_bits_long(gb, length*8);
  96.  
  97.     c->low = 0;
  98.     for (i = 0; i < 4; i++) {
  99.         c->low <<= 8;
  100.         if (c->bytestream < c->bytestream_end)
  101.             c->low |= *c->bytestream++;
  102.         else
  103.             c->low |= 0xff;
  104.     }
  105.  
  106.     c->counter = -16;
  107.     c->range   = 0xffff;
  108.  
  109.     for (i = 0; i < 256; i++) {
  110.         ff_dirac_prob_branchless[i][0] =  ff_dirac_prob[255-i];
  111.         ff_dirac_prob_branchless[i][1] = -ff_dirac_prob[i];
  112.     }
  113.  
  114.     for (i = 0; i < DIRAC_CTX_COUNT; i++)
  115.         c->contexts[i] = 0x8000;
  116. }
  117.