libavcodec/cabac.c
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 /*
  * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
  * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
  *
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  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
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  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
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  * version 2.1 of the License, or (at your option) any later version.
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  *
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  * FFmpeg is distributed in the hope that it will be useful,
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  * 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
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  * License along with FFmpeg; if not, write to the Free Software
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  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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  */
 
 /**
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  * @file
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  * Context Adaptive Binary Arithmetic Coder.
  */
 
 #include <string.h>
 
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 #include "libavutil/common.h"
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 #include "libavutil/timer.h"
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 #include "cabac.h"
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 #include "cabac_functions.h"
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 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
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 };
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 /**
  * @param buf_size size of buf in bits
  */
 void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size){
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     init_put_bits(&c->pb, buf, buf_size);
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     c->low= 0;
     c->range= 0x1FE;
     c->outstanding_count= 0;
     c->pb.bit_left++; //avoids firstBitFlag
 }
 
 /**
  *
  * @param buf_size size of buf in bits
  */
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 int ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
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     c->bytestream_start=
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     c->bytestream= buf;
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     c->bytestream_end= buf + buf_size;
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 #if CABAC_BITS == 16
     c->low =  (*c->bytestream++)<<18;
     c->low+=  (*c->bytestream++)<<10;
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     // Keep our fetches on a 2-byte boundary as this should avoid ever having to
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     // 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;
     }
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 #else
     c->low =  (*c->bytestream++)<<10;
     c->low+= ((*c->bytestream++)<<2) + 2;
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 #endif
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     c->range= 0x1FE;
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     if ((c->range<<(CABAC_BITS+1)) < c->low)
         return AVERROR_INVALIDDATA;
     return 0;
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 }