Dirac - A Video Codec

Created by the British Broadcasting Corporation.

---

dirac::ArithCodec< T >::Context Class Reference

A class for binary contexts. More...

#include <arith_codec.h>

Collaboration diagram for dirac::ArithCodec< T >::Context:

[legend]List of all members.

Public Member Functions

• Context ()

  Default Constructor.
  

• Context (int cnt0, int cnt1)

  Constructor.
  

• Context (const Context &cpy)

  Copy constructor.
  

• Context & operator= (const Context &rhs)

  Assignment=.
  

• ~Context ()

  Destructor.
  

• void SetCounts (int cnt0, int cnt1)

  Sets the counts according to the input.
  

• code_t GetCount0 () const

  Returns the count of zeroes.
  

• code_t GetCount1 () const

  Returns the count of ones.
  

• void IncrCount (const bool symbol, const int amnt)

  Increment the count.
  

• void IncrCount (const bool symbol)

  Increment the count by 1.
  

• void HalveCounts ()

  Divide the counts by 2, making sure neither ends up 0.
  

• code_t Weight () const

  Return the weight, equal to the count of 0 plus the count of 1.
  

• const Triple & GetTriple (const bool symbol) const

  Return the triple associated with Symbol.
  

• bool GetSymbol (const calc_t num, const calc_t factor, Triple &trip_val) const

  Given a number, return the corresponding symbol and triple.
  

Private Member Functions

• void SetTriples ()

Private Attributes

• code_t count0
• code_t count1
• Triple trip0
• Triple trip1

---

Detailed Description

template<class T>
class dirac::ArithCodec< T >::Context

A class for binary contexts. Stores probabilities for 0 and 1 in terms of counts of numbers of occurrences, and also as Triples partitioning the interval [0,1) into two parts [0,p) and [p,1).

---

Constructor & Destructor Documentation

template<class T> dirac::ArithCodec< T >::Context::Context (   )  [inline]

Default constructor initialises counts to 1 each of 0 and 1.

template<class T> dirac::ArithCodec< T >::Context::Context (  int  cnt0, int  cnt1 )  [inline]

Constructor initialises the counts to those set.

template<class T> dirac::ArithCodec< T >::Context::Context (  const Context &  cpy  )  [inline]

template<class T> dirac::ArithCodec< T >::Context::~Context (   )  [inline]

---

Member Function Documentation

template<class T> code_t dirac::ArithCodec< T >::Context::GetCount0 (   )  const [inline]

template<class T> code_t dirac::ArithCodec< T >::Context::GetCount1 (   )  const [inline]

template<class T> bool dirac::ArithCodec< T >::Context::GetSymbol (  const calc_t  num, const calc_t  factor, Triple &  trip_val )  const [inline]

Given a number, which should be in the range [0,m_weight) return the corresponding symbol. The range [0,m_weight) is partitioned into portions [0,count0), [count0,m_weight) corresponding to 0 and 1.

template<class T> const Triple& dirac::ArithCodec< T >::Context::GetTriple (  const bool  symbol  )  const [inline]

template<class T> void dirac::ArithCodec< T >::Context::HalveCounts (   )  [inline]

template<class T> void dirac::ArithCodec< T >::Context::IncrCount (  const bool  symbol  )  [inline]

Increment the count of symbol by 1. Parameters: symbol  the symbol whose count is to be incremented (false=0, true=1)

template<class T> void dirac::ArithCodec< T >::Context::IncrCount (  const bool  symbol, const int  amnt )  [inline]

Increment the count of Symbol by amnt. Parameters: symbol  the symbol whose count is to be incremented (false=0, true=1) amnt  the amount to increment by

template<class T> Context& dirac::ArithCodec< T >::Context::operator= (  const Context &  rhs  )  [inline]

template<class T> void dirac::ArithCodec< T >::Context::SetCounts (  int  cnt0, int  cnt1 )  [inline]

Sets the counts, and then the triples to reflect the counts.

template<class T> void dirac::ArithCodec< T >::Context::SetTriples (   )  [inline, private]

template<class T> code_t dirac::ArithCodec< T >::Context::Weight (   )  const [inline]

---

Member Data Documentation

template<class T> code_t dirac::ArithCodec< T >::Context::count0 [private]

template<class T> code_t dirac::ArithCodec< T >::Context::count1 [private]

template<class T> Triple dirac::ArithCodec< T >::Context::trip0 [private]

template<class T> Triple dirac::ArithCodec< T >::Context::trip1 [private]

---

The documentation for this class was generated from the following file:

• arith_codec.h

---

© 2004 British Broadcasting Corporation. Dirac code licensed under the Mozilla Public License (MPL) Version 1.1.
HTML documentation generated by Dimitri van Heesch's excellent Doxygen tool.