1 // Compress/RangeCoder/RangeCoderBit.cpp

     2 

     3 #include "StdAfx.h"

     4 

     5 #include "RangeCoderBit.h"

     6 

     7 namespace NCompress {

     8 namespace NRangeCoder {

     9 

    10 UInt32 CPriceTables::ProbPrices[kBitModelTotal >> kNumMoveReducingBits];

    11 static CPriceTables g_PriceTables;

    12 

    13 CPriceTables::CPriceTables() { Init(); }

    14 

    15 void CPriceTables::Init()

    16 {

    17   const int kNumBits = (kNumBitModelTotalBits - kNumMoveReducingBits);

    18   for(int i = kNumBits - 1; i >= 0; i--)

    19   {

    20     UInt32 start = 1 << (kNumBits - i - 1);

    21     UInt32 end = 1 << (kNumBits - i);

    22     for (UInt32 j = start; j < end; j++)

    23       ProbPrices[j] = (i << kNumBitPriceShiftBits) + 

    24           (((end - j) << kNumBitPriceShiftBits) >> (kNumBits - i - 1));

    25   }

    26 

    27   /*

    28   // simplest: bad solution

    29   for(UInt32 i = 1; i < (kBitModelTotal >> kNumMoveReducingBits) - 1; i++)

    30     ProbPrices[i] = kBitPrice;

    31   */

    32   

    33   /*

    34   const double kDummyMultMid = (1.0 / kBitPrice) / 2;

    35   const double kDummyMultMid = 0;

    36   // float solution

    37   double ln2 = log(double(2));

    38   double lnAll = log(double(kBitModelTotal >> kNumMoveReducingBits));

    39   for(UInt32 i = 1; i < (kBitModelTotal >> kNumMoveReducingBits) - 1; i++)

    40     ProbPrices[i] = UInt32((fabs(lnAll - log(double(i))) / ln2 + kDummyMultMid) * kBitPrice);

    41   */

    42   

    43   /*

    44   // experimental, slow, solution:

    45   for(UInt32 i = 1; i < (kBitModelTotal >> kNumMoveReducingBits) - 1; i++)

    46   {

    47     const int kCyclesBits = 5;

    48     const UInt32 kCycles = (1 << kCyclesBits);

    49 

    50     UInt32 range = UInt32(-1);

    51     UInt32 bitCount = 0;

    52     for (UInt32 j = 0; j < kCycles; j++)

    53     {

    54       range >>= (kNumBitModelTotalBits - kNumMoveReducingBits);

    55       range *= i;

    56       while(range < (1 << 31))

    57       {

    58         range <<= 1;

    59         bitCount++;

    60       }

    61     }

    62     bitCount <<= kNumBitPriceShiftBits;

    63     range -= (1 << 31);

    64     for (int k = kNumBitPriceShiftBits - 1; k >= 0; k--)

    65     {

    66       range <<= 1;

    67       if (range > (1 << 31))

    68       {

    69         bitCount += (1 << k);

    70         range -= (1 << 31);

    71       }

    72     }

    73     ProbPrices[i] = (bitCount 

    74       // + (1 << (kCyclesBits - 1))

    75       ) >> kCyclesBits;

    76   }

    77   */

    78 }

    79 

    80 }}