Mercurial > vba-linux

     1 // Compress/RangeCoderBit.h

     2 

     3 #ifndef __COMPRESS_RANGE_CODER_BIT_H

     4 #define __COMPRESS_RANGE_CODER_BIT_H

     5 

     6 #include "RangeCoder.h"

     7 

     8 namespace NCompress {

     9 namespace NRangeCoder {

    10 

    11 const int kNumBitModelTotalBits  = 11;

    12 const UInt32 kBitModelTotal = (1 << kNumBitModelTotalBits);

    13 

    14 const int kNumMoveReducingBits = 4;

    15 

    16 const int kNumBitPriceShiftBits = 4;

    17 const UInt32 kBitPrice = 1 << kNumBitPriceShiftBits;

    18 

    19 extern UInt32 ProbPrices[kBitModelTotal >> kNumMoveReducingBits];

    20 

    21 template <int numMoveBits>

    22 class CBitModel

    23 {

    24 public:

    25   UInt32 Prob;

    26   void UpdateModel(UInt32 symbol)

    27   {

    28     /*

    29     Prob -= (Prob + ((symbol - 1) & ((1 << numMoveBits) - 1))) >> numMoveBits;

    30     Prob += (1 - symbol) << (kNumBitModelTotalBits - numMoveBits);

    31     */

    32     if (symbol == 0)

    33       Prob += (kBitModelTotal - Prob) >> numMoveBits;

    34     else

    35       Prob -= (Prob) >> numMoveBits;

    36   }

    37 public:

    38   void Init() { Prob = kBitModelTotal / 2; }

    39 };

    40 

    41 template <int numMoveBits>

    42 class CBitEncoder: public CBitModel<numMoveBits>

    43 {

    44 public:

    45   void Encode(CEncoder *encoder, UInt32 symbol)

    46   {

    47     /*

    48     encoder->EncodeBit(this->Prob, kNumBitModelTotalBits, symbol);

    49     this->UpdateModel(symbol);

    50     */

    51     UInt32 newBound = (encoder->Range >> kNumBitModelTotalBits) * this->Prob;

    52     if (symbol == 0)

    53     {

    54       encoder->Range = newBound;

    55       this->Prob += (kBitModelTotal - this->Prob) >> numMoveBits;

    56     }

    57     else

    58     {

    59       encoder->Low += newBound;

    60       encoder->Range -= newBound;

    61       this->Prob -= (this->Prob) >> numMoveBits;

    62     }

    63     if (encoder->Range < kTopValue)

    64     {

    65       encoder->Range <<= 8;

    66       encoder->ShiftLow();

    67     }

    68   }

    69   UInt32 GetPrice(UInt32 symbol) const

    70   {

    71     return ProbPrices[(this->Prob ^ ((-(int)symbol)) & (kBitModelTotal - 1)) >> kNumMoveReducingBits];

    72   }

    73   UInt32 GetPrice0() const { return ProbPrices[this->Prob >> kNumMoveReducingBits]; }

    74   UInt32 GetPrice1() const { return ProbPrices[(this->Prob ^ (kBitModelTotal - 1)) >> kNumMoveReducingBits]; }

    75 };

    76 

    77 

    78 template <int numMoveBits>

    79 class CBitDecoder: public CBitModel<numMoveBits>

    80 {

    81 public:

    82   UInt32 Decode(CDecoder *decoder)

    83   {

    84     UInt32 newBound = (decoder->Range >> kNumBitModelTotalBits) * this->Prob;

    85     if (decoder->Code < newBound)

    86     {

    87       decoder->Range = newBound;

    88       this->Prob += (kBitModelTotal - this->Prob) >> numMoveBits;

    89       if (decoder->Range < kTopValue)

    90       {

    91         decoder->Code = (decoder->Code << 8) | decoder->Stream.ReadByte();

    92         decoder->Range <<= 8;

    93       }

    94       return 0;

    95     }

    96     else

    97     {

    98       decoder->Range -= newBound;

    99       decoder->Code -= newBound;

   100       this->Prob -= (this->Prob) >> numMoveBits;

   101       if (decoder->Range < kTopValue)

   102       {

   103         decoder->Code = (decoder->Code << 8) | decoder->Stream.ReadByte();

   104         decoder->Range <<= 8;

   105       }

   106       return 1;

   107     }

   108   }

   109 };

   110 

   111 }}

   112 

   113 #endif
author	Robert McIntyre <rlm@mit.edu>
date	Sat, 03 Mar 2012 10:31:27 -0600
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