RangeCoder< UInt > Class Template Reference

Base class for entropy coding with range encoder and decoder. More...

#include <rangecoder.hh>

Detailed Description

template<class UInt>
class RangeCoder< UInt >

Base class for entropy coding with range encoder and decoder.

The coding works on sequences \( (s_i)_i \) of symbols. The symbols \( s_i \) are elements of an alphabet \( S_i \), which may be a different one for any position \( i \).

Each symbol \( s \) is a pair of values \( (s_{\text{low}},s_{\text{high}}) \) with \( s_{\text{low}} < s_{\text{high}} \). Symbols represent half-open integer ranges. Symbols from the same alphabet are non-overlapping, i.e., \( s,t\in S \Rightarrow s_{\text{high}} \le t_{\text{low}} \vee t_{\text{high}} \le s_{\text{low}} \).

Each alphabet \( S \) is a setof nonoverlapping symbols such that \( s_{\text{high}} \le \text{maxRange} \) for all \( s\in S \).

Note that the range coder is not self-terminating. That means that spurious trailing symbols can be extracted. For a correct termination of the symbol sequence on decoding, you either need to transmit the length of the symbol sequence beforehand or define a special EOF symbol.

The range coder algorithm is derived from the implementation by Dmitry Subbotin. See also https://en.wikipedia.org/wiki/Range_encoding.

Template Parameters

UInt	an unsigned integral type with more than 16 bits (usually 32 or 64 bit usigned integer).

Definition at line 62 of file rangecoder.hh.

Inheritance diagram for RangeCoder< UInt >:

Public Member Functions
size_t	size () const
	Number of processed encoded bytes. More...

Static Public Attributes
static const UInt	maxRange = bottom
	Maximal total range of alphabets. More...

Protected Member Functions
	RangeCoder ()

Protected Attributes
UInt	low
UInt	range
size_t	count

Static Protected Attributes
static int const	digits = std::numeric_limits<UInt>::digits
static UInt const	top = static_cast<UInt>(1) << (digits-8)
static UInt const	bottom = static_cast<UInt>(1) << (digits-16)

Constructor & Destructor Documentation

RangeCoder()

template<class UInt >

RangeCoder< UInt >::RangeCoder ( )

inlineprotected

Definition at line 105 of file rangecoder.hh.

Member Function Documentation

size()

template<class UInt >

size_t RangeCoder< UInt >::size ( ) const

inline

Number of processed encoded bytes.

When encoding, this is the number of bytes already written to the output stream. When decoding, this is the number of bytes already read from the input stream.

Definition at line 100 of file rangecoder.hh.

Member Data Documentation

bottom

template<class UInt >

UInt const RangeCoder< UInt >::bottom = static_cast<UInt>(1) << (digits-16)

staticprotected

Definition at line 85 of file rangecoder.hh.

count

template<class UInt >

size_t RangeCoder< UInt >::count

protected

Definition at line 114 of file rangecoder.hh.

Referenced by RangeDecoder< UInt >::pop(), RangeDecoder< UInt >::RangeDecoder(), and RangeCoder< UInt >::size().

digits

template<class UInt >

int const RangeCoder< UInt >::digits = std::numeric_limits<UInt>::digits

staticprotected

Definition at line 66 of file rangecoder.hh.

Referenced by RangeCoder< UInt >::RangeCoder().

low

template<class UInt >

UInt RangeCoder< UInt >::low

protected

Definition at line 113 of file rangecoder.hh.

Referenced by RangeDecoder< UInt >::front(), RangeDecoder< UInt >::pop(), and RangeEncoder< UInt >::push().

maxRange

template<class UInt >

const UInt RangeCoder< UInt >::maxRange = bottom

static

Maximal total range of alphabets.

Definition at line 91 of file rangecoder.hh.

range

template<class UInt >

UInt RangeCoder< UInt >::range

protected

Definition at line 113 of file rangecoder.hh.

Referenced by RangeDecoder< UInt >::front(), RangeDecoder< UInt >::pop(), and RangeEncoder< UInt >::push().

top

template<class UInt >

UInt const RangeCoder< UInt >::top = static_cast<UInt>(1) << (digits-8)

staticprotected

Definition at line 76 of file rangecoder.hh.

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

• rangecoder.hh