libdirac_encoder/quant_chooser.h

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  16 * The Original Code is BBC Research and Development code.
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  23 * Contributor(s): Thomas Davies (Original Author)
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  37
  38
  39 #ifndef _QUANT_CHOOSER_H_
  40 #define _QUANT_CHOOSER_H_
  41
  42 #include <libdirac_common/arrays.h>
  43 #include <libdirac_common/wavelet_utils.h>
  44 #include <libdirac_common/common.h>
  45
  46 namespace dirac
  47 {
  48     //! Choose a quantiser
  49     /*!
  50         This class chooses a quantiser or quantisers for a subband
  51     */
  52     class QuantChooser
  53     {
  54     public:
  55
  56         //! Constructor
  57         QuantChooser( const CoeffArray& pic_data , const float lambda  );
  58
  59         //! Finds the best quantisers for the subband, returning the predicted number of bits needed
  60         int GetBestQuant( Subband& node );
  61
  62         //! Sets the factor used for correcting the entropy calculation
  63         void SetEntropyCorrection( const float ecfac ){ m_entropy_correctionfactor = ecfac; }
  64     private:
  65         //! Copy constructor is private and body-less. This class should not be copied.
  66         QuantChooser(const QuantChooser& cpy);
  67
  68         //! Assignment = is private and body-less. This class should not be assigned.
  69         QuantChooser& operator=(const QuantChooser& rhs);
  70
  71         //! Calculate errors and entropies for integral-bit quantisers
  72         void IntegralErrorCalc( Subband& node , const int xratio , const int yratio );
  73
  74         //! Calculate errors and entropies for non-integral-bit quantisers
  75         void NonIntegralErrorCalc( Subband& node, const int xratio, const int yratio );
  76
  77         //! Having got statistics, calculate the Lagrangian costs
  78         void LagrangianCalc();
  79
  80         //! Select the best quantisation index on the basis of the Lagrangian calculations
  81         void SelectBestQuant();
  82
  83         CoeffType BlockAbsMax( const Subband& node );
  84
  85         //! Set the skip flag for a codeblock
  86         void SetSkip( CodeBlock& cblock , const int qidx);
  87
  88     private:
  89         //! The perceptual weighting factor of the subband being tested
  90         float m_subband_wt;
  91
  92         //! The smallest quantisation index being tested
  93         int m_bottom_idx;
  94         //! The largest quantisation index being tested
  95         int m_top_idx;
  96         //! The step we use in jumping through the list of quantisers
  97         int m_index_step;
  98
  99         //! The index of the quantiser with the lowest cost
 100         int m_min_idx;
 101
 102         //! A local reference to the data under consideration
 103         const CoeffArray& m_coeff_data;
 104
 105         //!  The lambda value to be used in the Lagrangian calculation
 106         const float m_lambda;
 107
 108         //! A value for correcting the crude calculation of the entropy
 109         float m_entropy_correctionfactor;
 110
 111         //! An array used to count the number of zeroes
 112         OneDArray<int> m_count0;
 113         //! The number of ones (equal to the number of coefficients)
 114         int m_count1;
 115         //! An array used to count the number of positive values
 116         OneDArray<int> m_countPOS;
 117         //! An array used to count the number of negative values
 118         OneDArray<int> m_countNEG;
 119         //! An array used to collate the sum of the perceptually-weighted errors
 120         OneDArray<double> m_error_total;
 121         //! An array used to collate the computed costs
 122         OneDArray<CostType> m_costs;
 123
 124     };
 125
 126 } // namespace dirac
 127
 128
 129
 130 #endif