OpalSilenceDetector Class Reference

#include <silencedetect.h>

Inheritance diagram for OpalSilenceDetector:

Data Structures
struct	Params

Public Types
typedef Modes	Mode

Public Member Functions
	P_DECLARE_STREAMABLE_ENUM (Modes, NoSilenceDetection, FixedSilenceDetection, AdaptiveSilenceDetection)
Construction
	OpalSilenceDetector (const Params &newParam)

Basic operations
enum	Result { IsSilent, VoiceActivated, VoiceActive }
PNotifier	m_receiveHandler
Mode	m_mode
unsigned	m_signalDeadband
unsigned	m_silenceDeadband
unsigned	m_adaptivePeriod
unsigned	m_clockRate
unsigned	m_lastTimestamp
unsigned	m_receivedTime
unsigned	m_levelThreshold
unsigned	m_signalMinimum
unsigned	m_silenceMaximum
unsigned	m_signalReceivedTime
unsigned	m_silenceReceivedTime
unsigned	m_lastSignalLevel
Result	m_lastResult
const PNotifier &	GetReceiveHandler () const
void	SetParameters (const Params &params, const int clockRate=0)
void	GetParameters (Params &params)
void	SetClockRate (unsigned clockRate)
unsigned	GetClockRate () const
Result	GetResult (unsigned *currentThreshold=NULL, unsigned *currentLevel=NULL) const
Result	Detect (const BYTE *audioPtr, PINDEX audioLen, unsigned timestamp)
virtual unsigned	GetAverageSignalLevel (const BYTE *buffer, PINDEX size)=0
static unsigned	GetAverageSignalLevelPCM16 (const BYTE *buffer, PINDEX size, bool asPercentage)
	PDECLARE_NOTIFIER (RTP_DataFrame, OpalSilenceDetector, ReceivedPacket)
	PDECLARE_MUTEX (m_inUse)

Detailed Description

Implement silence detection of audio. This is the complement of Voice Activity Detection (VAD) and can be used for that purpose.

Member Typedef Documentation

typedef Modes OpalSilenceDetector::Mode

Member Enumeration Documentation

enum OpalSilenceDetector::Result

Enumerator
IsSilent
VoiceActivated
VoiceActive

Constructor & Destructor Documentation

OpalSilenceDetector::OpalSilenceDetector

(

const Params &

newParam

)

Create a new detector. Default clock rate is 8000.

Parameters

newParam

New parameters for silence detector

Member Function Documentation

Result OpalSilenceDetector::Detect	(	const BYTE *	audioPtr,
		PINDEX	audioLen,
		unsigned	timestamp
	)

Detemine (in context) if audio stream is currently silent.

virtual unsigned OpalSilenceDetector::GetAverageSignalLevel ( const BYTE *  buffer, PINDEX  size  )

pure virtual

Get the average signal level in the stream. This is called from within the silence detection algorithm to calculate the average signal level of the last data frame read from the stream.

The default behaviour returns UINT_MAX which indicates that the average signal has no meaning for the stream.

Parameters

buffer	RTP payload being detected
size	Size of payload buffer

Implemented in OpalLineSilenceDetector, and OpalPCM16SilenceDetector.

static unsigned OpalSilenceDetector::GetAverageSignalLevelPCM16 ( const BYTE *  buffer, PINDEX  size, bool  asPercentage  )

static

Get the average signal level in the stream. This is called from within the silence detection algorithm to calculate the average signal level of the last data frame read from the stream.

The default behaviour returns UINT_MAX which indicates that the average signal has no meaning for the stream.

Parameters

buffer	RTP payload being detected
size	Size of payload buffer
asPercentage	Return as percentage on logarithmic scale

unsigned OpalSilenceDetector::GetClockRate ( ) const

inline

Get the current sampling clock rate.

References m_clockRate.

void OpalSilenceDetector::GetParameters

(

Params &

params

)

Get the current parameters in use.

const PNotifier& OpalSilenceDetector::GetReceiveHandler ( ) const

inline

References m_receiveHandler.

Result OpalSilenceDetector::GetResult	(	unsigned *	currentThreshold = NULL,
		unsigned *	currentLevel = NULL
	)		const

Get silence detection status

The currentThreshold value for energy value as logarithmic scale from 0 to 255 (actually a u-Law value) which is used as the threshold value for audio signal.

The currentLevel value is the energy as logarithmic scale from 0 to 255 (actually a u-Law value) for last audio frame.

OpalSilenceDetector::P_DECLARE_STREAMABLE_ENUM	(	Modes	,
		NoSilenceDetection	,
		FixedSilenceDetection	,
		AdaptiveSilenceDetection
	)

OpalSilenceDetector::PDECLARE_MUTEX ( m_inUse  )

protected

OpalSilenceDetector::PDECLARE_NOTIFIER ( RTP_DataFrame  , OpalSilenceDetector  , ReceivedPacket    )

protected

void OpalSilenceDetector::SetClockRate

(

unsigned

clockRate

)

Set the sampling clock rate for the preprocessor. Adusts the interpretation of time values. This may be called while audio is being transferred, but if in adaptive mode calling this will reset the filter.

Parameters

clockRate

Sampling clock rate for the preprocessor

void OpalSilenceDetector::SetParameters	(	const Params &	params,
		const int	clockRate = 0
	)

Set the silence detector parameters. This adjusts the silence detector "agression". The deadband and adaptive periods are in ms units to work for any clock rate. The clock rate value is optional: 0 leaves value unchanged. This may be called while audio is being transferred, but if in adaptive mode calling this will reset the filter.

Parameters

params	New parameters for silence detector
clockRate	Sampling clock rate for the preprocessor

Field Documentation

unsigned OpalSilenceDetector::m_adaptivePeriod

protected

unsigned OpalSilenceDetector::m_clockRate

protected

Referenced by GetClockRate().

Result OpalSilenceDetector::m_lastResult

protected

unsigned OpalSilenceDetector::m_lastSignalLevel

protected

unsigned OpalSilenceDetector::m_lastTimestamp

protected

unsigned OpalSilenceDetector::m_levelThreshold

protected

Mode OpalSilenceDetector::m_mode

protected

unsigned OpalSilenceDetector::m_receivedTime

protected

PNotifier OpalSilenceDetector::m_receiveHandler

protected

Referenced by GetReceiveHandler().

unsigned OpalSilenceDetector::m_signalDeadband

protected

unsigned OpalSilenceDetector::m_signalMinimum

protected

unsigned OpalSilenceDetector::m_signalReceivedTime

protected

unsigned OpalSilenceDetector::m_silenceDeadband

protected

unsigned OpalSilenceDetector::m_silenceMaximum

protected

unsigned OpalSilenceDetector::m_silenceReceivedTime

protected

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

• silencedetect.h