FFmpeg/libavcodec/cabac.c

/*
 * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * Context Adaptive Binary Arithmetic Coder.
 */

#include <string.h>

#include "libavutil/common.h"
#include "libavutil/timer.h"

#include "cabac.h"
#include "cabac_functions.h"

const uint8_t ff_h264_cabac_tables[512 + 4*2*64 + 4*64 + 63] = {
    9,8,7,7,6,6,6,6,5,5,5,5,5,5,5,5,
    4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
    3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
    3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
    2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
    2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
    2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
    2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    // LPS range
    -128,    -128,    -128,    -128,    -128,    -128,    123,     123,
    116,     116,     111,     111,     105,     105,     100,     100,
    95,      95,      90,      90,      85,      85,      81,      81,
    77,      77,      73,      73,      69,      69,      66,      66,
    62,      62,      59,      59,      56,      56,      53,      53,
    51,      51,      48,      48,      46,      46,      43,      43,
    41,      41,      39,      39,      37,      37,      35,      35,
    33,      33,      32,      32,      30,      30,      29,      29,
    27,      27,      26,      26,      24,      24,      23,      23,
    22,      22,      21,      21,      20,      20,      19,      19,
    18,      18,      17,      17,      16,      16,      15,      15,
    14,      14,      14,      14,      13,      13,      12,      12,
    12,      12,      11,      11,      11,      11,      10,      10,
    10,      10,      9,       9,       9,       9,       8,       8,
    8,       8,       7,       7,       7,       7,       7,       7,
    6,       6,       6,       6,       6,       6,       2,       2,
    -80,     -80,     -89,     -89,     -98,     -98,     -106,    -106,
    -114,    -114,    -121,    -121,    -128,    -128,    122,     122,
    116,     116,     110,     110,     104,     104,     99,      99,
    94,      94,      89,      89,      85,      85,      80,      80,
    76,      76,      72,      72,      69,      69,      65,      65,
    62,      62,      59,      59,      56,      56,      53,      53,
    50,      50,      48,      48,      45,      45,      43,      43,
    41,      41,      39,      39,      37,      37,      35,      35,
    33,      33,      31,      31,      30,      30,      28,      28,
    27,      27,      26,      26,      24,      24,      23,      23,
    22,      22,      21,      21,      20,      20,      19,      19,
    18,      18,      17,      17,      16,      16,      15,      15,
    14,      14,      14,      14,      13,      13,      12,      12,
    12,      12,      11,      11,      11,      11,      10,      10,
    9,       9,       9,       9,       9,       9,       8,       8,
    8,       8,       7,       7,       7,       7,       2,       2,
    -48,     -48,     -59,     -59,     -69,     -69,     -78,     -78,
    -87,     -87,     -96,     -96,     -104,    -104,    -112,    -112,
    -119,    -119,    -126,    -126,    123,     123,     117,     117,
    111,     111,     105,     105,     100,     100,     95,      95,
    90,      90,      86,      86,      81,      81,      77,      77,
    73,      73,      69,      69,      66,      66,      63,      63,
    59,      59,      56,      56,      54,      54,      51,      51,
    48,      48,      46,      46,      43,      43,      41,      41,
    39,      39,      37,      37,      35,      35,      33,      33,
    32,      32,      30,      30,      29,      29,      27,      27,
    26,      26,      25,      25,      23,      23,      22,      22,
    21,      21,      20,      20,      19,      19,      18,      18,
    17,      17,      16,      16,      15,      15,      15,      15,
    14,      14,      13,      13,      12,      12,      12,      12,
    11,      11,      11,      11,      10,      10,      10,      10,
    9,       9,       9,       9,       8,       8,       2,       2,
    -16,     -16,     -29,     -29,     -40,     -40,     -51,     -51,
    -61,     -61,     -71,     -71,     -81,     -81,     -90,     -90,
    -98,     -98,     -106,    -106,    -114,    -114,    -121,    -121,
    -128,    -128,    122,     122,     116,     116,     110,     110,
    104,     104,     99,      99,      94,      94,      89,      89,
    85,      85,      80,      80,      76,      76,      72,      72,
    69,      69,      65,      65,      62,      62,      59,      59,
    56,      56,      53,      53,      50,      50,      48,      48,
    45,      45,      43,      43,      41,      41,      39,      39,
    37,      37,      35,      35,      33,      33,      31,      31,
    30,      30,      28,      28,      27,      27,      25,      25,
    24,      24,      23,      23,      22,      22,      21,      21,
    20,      20,      19,      19,      18,      18,      17,      17,
    16,      16,      15,      15,      14,      14,      14,      14,
    13,      13,      12,      12,      12,      12,      11,      11,
    11,      11,      10,      10,      9,       9,       2,       2,
    // mlps state
    127,     126,     77,      76,      77,      76,      75,      74,
    75,      74,      75,      74,      73,      72,      73,      72,
    73,      72,      71,      70,      71,      70,      71,      70,
    69,      68,      69,      68,      67,      66,      67,      66,
    67,      66,      65,      64,      65,      64,      63,      62,
    61,      60,      61,      60,      61,      60,      59,      58,
    59,      58,      57,      56,      55,      54,      55,      54,
    53,      52,      53,      52,      51,      50,      49,      48,
    49,      48,      47,      46,      45,      44,      45,      44,
    43,      42,      43,      42,      39,      38,      39,      38,
    37,      36,      37,      36,      33,      32,      33,      32,
    31,      30,      31,      30,      27,      26,      27,      26,
    25,      24,      23,      22,      23,      22,      19,      18,
    19,      18,      17,      16,      15,      14,      13,      12,
    11,      10,      9,       8,       9,       8,       5,       4,
    5,       4,       3,       2,       1,       0,       0,       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,     124,     125,     126,     127,
    // last_coeff_flag_offset_8x8
    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
    3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4,
    5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8
};

/**
 * @param buf_size size of buf in bits
 */
void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size){
    init_put_bits(&c->pb, buf, buf_size);

    c->low= 0;
    c->range= 0x1FE;
    c->outstanding_count= 0;
    c->pb.bit_left++; //avoids firstBitFlag
}

/**
 *
 * @param buf_size size of buf in bits
 */
int ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
    c->bytestream_start=
    c->bytestream= buf;
    c->bytestream_end= buf + buf_size;

#if CABAC_BITS == 16
    c->low =  (*c->bytestream++)<<18;
    c->low+=  (*c->bytestream++)<<10;
    // Keep our fetches on a 2-byte boundary as this should avoid ever having to
    // do unaligned loads if the compiler (or asm) optimises the double byte
    // load into a single instruction
    if(((uintptr_t)c->bytestream & 1) == 0) {
        c->low += (1 << 9);
    }
    else {
        c->low += ((*c->bytestream++) << 2) + 2;
    }
#else
    c->low =  (*c->bytestream++)<<10;
    c->low+= ((*c->bytestream++)<<2) + 2;
#endif
    c->range= 0x1FE;
    if ((c->range<<(CABAC_BITS+1)) < c->low)
        return AVERROR_INVALIDDATA;
    return 0;
}