SPL::BinArithDecoder Class Reference

Binary arithmetic decoder class. More...

#include <arithCoder.hpp>

Public Member Functions
	BinArithDecoder (int numContexts, InputBitStream *in=nullptr)
	Create a decoder with the specified number of contexts that receives input from the given bit stream. More...
	~BinArithDecoder ()
	Destroy a decoder. More...
SPL_ArithCoder_ulong	getSymCount () const
	Get the number of symbols decoded so far. More...
SPL_ArithCoder_ulong	getBitCount () const
	Get the number of bits read so far. More...
void	setInput (InputBitStream *in)
	Set the bit stream from which to read encoded data. More...
InputBitStream *	getInput () const
	Get the bit stream from which to read encoded data. More...
int	getNumContexts () const
	Get the number of contexts. More...
void	setContextState (int contextId, ArithCoder::Freq oneFreq, ArithCoder::Freq totalFreq, ArithCoder::Freq maxFreq, bool adaptive)
	Set the symbol probabilities and adaptivity for the specified context. More...
void	getContextState (int contextId, ArithCoder::Freq &oneFreq, ArithCoder::Freq &totalFreq, ArithCoder::Freq &maxFreq, bool &adaptive)
	Get the symbol probabilities and adaptivity for the specified context. More...
int	start ()
	Start a code word. More...
int	terminate ()
	Terminate the code word (for synchonization with the encoder). More...
int	decodeRegular (int contextId)
	Decode a symbol in the specified context. More...
int	decodeBypass ()
	Decode a symbol in bypass mode (i.e., using a fixed probability distribution with all symbols being equiprobable). More...
void	dump (std::ostream &out) const
	Dump the internal decoder state to the specified stream for debugging purposes. More...

Static Public Member Functions
static void	setDebugLevel (int debugLevel)
	Set the debug level. More...
static void	setDebugStream (std::ostream &out)
	Set the stream to be used for debugging output. More...
static std::ostream &	getDebugStream ()
	Get the stream used for debugging output. More...

Detailed Description

Binary arithmetic decoder class.

Constructor & Destructor Documentation

SPL::BinArithDecoder::BinArithDecoder	(	int	numContexts,
		InputBitStream *	in = nullptr
	)

Create a decoder with the specified number of contexts that receives input from the given bit stream.

Parameters

numContexts	The number of contexts.
in	The input bit stream.

This function creates an arithmetic decoder with the number of contexts being numContexts that receives input from the bit stream in.

SPL::BinArithDecoder::~BinArithDecoder

(

)

Destroy a decoder.

This function destroys an arithmetic decoder.

Member Function Documentation

int SPL::BinArithDecoder::decodeBypass

(

)

Decode a symbol in bypass mode (i.e., using a fixed probability distribution with all symbols being equiprobable).

This function decodes a symbol in bypass mode (i.e., using a fixed probability distribution with all symbols being equiprobable).

Returns

Upon success, the decoded symbol is returned (which is either 0 or 1); otherwise, a negative value is returned.

int SPL::BinArithDecoder::decodeRegular

(

int

contextId

)

Decode a symbol in the specified context.

Parameters

contextId

The ID of the context to be used for decoding.

The function decodes a symbol using the context specified by contextId. The value of contextId must be from 0 to n - 1 (inclusive), where n is the number of contexts employed by the arithmetic decoder.

Returns

Upon success, the decoded symbol is returned (which is either 0 or 1); otherwise, a negative value is returned.

void SPL::BinArithDecoder::dump

(

std::ostream &

out

)

const

Dump the internal decoder state to the specified stream for debugging purposes.

void SPL::BinArithDecoder::getContextState	(	int	contextId,
		ArithCoder::Freq &	oneFreq,
		ArithCoder::Freq &	totalFreq,
		ArithCoder::Freq &	maxFreq,
		bool &	adaptive
	)

Get the symbol probabilities and adaptivity for the specified context.

Parameters

	contextId	The ID of the context to query.
[out]	oneFreq	The frequency count for a one symbol.
[out]	totalFreq	The normalizing frequency count for all symbols.
[out]	maxFreq	The maximum normalizing frequency count.
[out]	adaptive	The adaptivity flag.

This function queries the state of the context with the context ID contextId, and sets the parameters oneFreq, totalFreq, maxFreq, and adaptive appropriately. The probability of a one symbol is given by oneFreq / totalFreq, while the probability of a zero symbol is given by 1 - oneFreq / totalFreq.

void SPL::BinArithDecoder::setContextState	(	int	contextId,
		ArithCoder::Freq	oneFreq,
		ArithCoder::Freq	totalFreq,
		ArithCoder::Freq	maxFreq,
		bool	adaptive
	)

Set the symbol probabilities and adaptivity for the specified context.

int SPL::BinArithDecoder::start

(

)

Start a code word.

This function starts the decoding of a new arithmetic code word. This function must be called before attempting to decode any symbols.

Returns

Upon success, zero is returned; otherwise, a nonzero value is returned.

int SPL::BinArithDecoder::terminate

(

)

Terminate the code word (for synchonization with the encoder).

This function terminates the decoding of the current arithmetic code word.

Returns

Upon success, zero is returned; otherwise, a nonzero value is returned.

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

• arithCoder.hpp
• arithCoder.cpp