A class that reduces the level of sound that is below a certain threshold. More...

#include <omSoundExpander.h>

Inheritance diagram for om::sound::filters::Expander:

Public Member Functions
	Expander ()
	Create a new expander with the default compression parameters. More...

	Expander (Gain threshold, Float ratio, Float attack, Float hold, Float release)
	Create a new expander with specified threshold, ratio, attack, hold, and release. More...

Gain	getThreshold () const
	Return the linear full-scale value below which the expander applies gain reduction. More...

Gain	getThresholdDB () const
	Return the logarithmic full-scale value below which the expander applies gain reduction. More...

void	setThreshold (Gain newThreshold)
	Set the linear full-scale value below which the expander applies gain reduction. More...

void	setThresholdDB (Gain newThresholdDB)
	Set the logarithmic full-scale value below which the expander applies gain reduction. More...

Float	getRatio () const
	Return the downward expansion ratio that the expander is using. More...

void	setRatio (Float newRatio)
	Set the downward expansion ratio that the expander is using. More...

Gain	getKnee () const
	Return the knee radius of this expander in decibels. More...

void	setKnee (Gain newKnee)
	Set the knee radius of this expander in decibels. More...

Float	getAttack () const
	Return the attack of this expander in seconds. More...

void	setAttack (Float newAttack)
	Set the attack of this expander in seconds. More...

Float	getHold () const
	Return the hold time of this expander in seconds. More...

void	setHold (Float newHold)
	Set the hold time of this expander in seconds. More...

Float	getRelease () const
	Return the release of this expander in seconds. More...

void	setRelease (Float newRelease)
	Set the release of this expander in seconds. More...

Bool	getChannelsAreLinked () const
	Return whether or not all channels in the expander are linked together. More...

void	setChannelsAreLinked (Bool newChannelsAreLinked)
	Set whether or not all channels in the expander are linked together. More...

Gain	getGainReductionDB () const
	Return the current gain reduction of the expander in decibels. More...

Gain	getGainReduction () const
	Return the current gain reduction of the expander on a linear scale. More...

Gain	evaluateTransferFunction (Gain input) const
	Evaluate the transfer function of the expander for an envelope with the specified amplitude. More...

Gain	evaluateTransferFunctionDB (Gain input) const
	Evaluate the transfer function of the expander for an envelope with the specified amplitude in decibels. More...

virtual UTF8String	getInputName (Index inputIndex) const
	Return a human-readable name of the expander input at the specified index. More...

virtual UTF8String	getName () const
	Return a human-readable name for this expander. More...

virtual UTF8String	getManufacturer () const
	Return the manufacturer name of this expander. More...

virtual FilterVersion	getVersion () const
	Return an object representing the version of this expander. More...

virtual FilterCategory	getCategory () const
	Return an object that describes the category of effect that this filter implements. More...

virtual Bool	allowsInPlaceProcessing () const
	Return whether or not this expander can process audio data in-place. More...

virtual Size	getParameterCount () const
	Return the total number of generic accessible parameters this filter has. More...

virtual Bool	getParameterInfo (Index parameterIndex, FilterParameterInfo &info) const
	Get information about the filter parameter at the specified index. More...

Public Member Functions inherited from om::sound::filters::SoundFilter
virtual	~SoundFilter ()
	Destroy this sound filter object. More...

SoundResult	read (SoundBuffer &outputBuffer, Size numSamples)
	Fill the specified output buffer with the requested number of samples, based on internal filter state. More...

SoundResult	read (SoundFrame &outputFrame, Size numSamples)
	Fill the specified output frame with the requested number of samples, based on internal filter state. More...

SoundResult	write (const SoundBuffer &inputBuffer, Size numSamples)
	Process the specified input buffer samples and do something with them. More...

SoundResult	write (const SoundFrame &inputFrame, Size numSamples)
	Process the specified input frame samples and do something with them. More...

SoundResult	process (const SoundBuffer &inputBuffer, SoundBuffer &outputBuffer, Size numSamples)
	Apply this filter to the specified input buffer data, placing the result in the output buffer. More...

SoundResult	process (const SoundBuffer &inputBuffer, SoundFrame &outputFrame, Size numSamples)
	Apply this filter to the specified input buffer data, placing the result in the output frame. More...

SoundResult	process (const SoundFrame &inputFrame, SoundFrame &outputFrame, Size numSamples)
	Apply this filter to the specified input frame data, placing the result in the output frame. More...

SoundResult	process (const SoundFrame &inputBuffer, SoundBuffer &outputBuffer, Size numSamples)
	Apply this filter to the specified input frame data, placing the result in the output buffer. More...

void	reset ()
	Signal to the filter that the audio stream is restarting. More...

UInt64	getFrameIndex () const
	Return the index of the next frame to be processed (or the current one if currently processing). More...

Size	getInputCount () const
	Return the current number of audio inputs that this filter has. More...

Size	getOutputCount () const
	Return the current number of audio outputs that this filter has. More...

virtual UTF8String	getOutputName (Index outputIndex) const
	Return a human-readable name of the filter audio output at the specified index. More...

Size	getMIDIInputCount () const
	Return the current number of MIDI inputs that this filter has. More...

virtual UTF8String	getMIDIInputName (Index inputIndex) const
	Return a human-readable name of the filter MIDI input at the specified index. More...

Size	getMIDIOutputCount () const
	Return the current number of MIDI outputs that this filter has. More...

virtual UTF8String	getMIDIOutputName (Index outputIndex) const
	Return a human-readable name of the filter MIDI output at the specified index. More...

virtual Time	getLatency () const
	Return a Time value indicating the latency of this sound filter in seconds. More...

virtual Bool	getParameterIndex (const UTF8String &parameterName, Index &parameterIndex) const
	Query the index of the parameter with the specified name. More...

virtual Bool	getParameterValueName (Index parameterIndex, const FilterParameter &value, UTF8String &name) const
	Get any special name associated with the specified value of an indexed parameter. More...

Bool	getParameter (Index parameterIndex, FilterParameter &value) const
	Place the value of the parameter at the specified index in the output parameter. More...

Bool	getParameter (Index parameterIndex, Bool &value) const
	Place the value of the parameter at the specified index in the output parameter. More...

Bool	getParameter (Index parameterIndex, Int64 &value) const
	Place the value of the parameter at the specified index in the output parameter. More...

Bool	getParameter (Index parameterIndex, Float32 &value) const
	Place the value of the parameter at the specified index in the output parameter. More...

Bool	getParameter (Index parameterIndex, Float64 &value) const
	Place the value of the parameter at the specified index in the output parameter. More...

template<typename ParameterType >
Bool	getParameter (const UTF8String &name, ParameterType &value) const
	Place the value of the parameter with the specified name in the output parameter. More...

template<typename ParameterType >
Bool	getParameter (const char *name, ParameterType &value) const
	Place the value of the parameter with the specified name in the output parameter. More...

Bool	setParameter (Index parameterIndex, const FilterParameter &value)
	Attempt to set the parameter value at the specified index. More...

Bool	setParameter (Index parameterIndex, Bool value)
	Attempt to set the parameter value at the specified index. More...

Bool	setParameter (Index parameterIndex, Int64 value)
	Attempt to set the parameter value at the specified index. More...

Bool	setParameter (Index parameterIndex, Float32 value)
	Attempt to set the parameter value at the specified index. More...

Bool	setParameter (Index parameterIndex, Float64 value)
	Attempt to set the parameter value at the specified index. More...

template<typename ParameterType >
Bool	setParameter (const UTF8String &name, ParameterType value)
	Attempt to set the parameter value with the specified name. More...

template<typename ParameterType >
Bool	setParameter (const char *name, ParameterType value)
	Attempt to set the parameter value with the specified name. More...

virtual Bool	writeState (DataOutputStream &stream) const
	Write the current state of this sound filter to a data output stream. More...

virtual Bool	readState (DataInputStream &stream)
	Read a previously saved filter state from the specified data input stream and replace the filter's state. More...

virtual Size	getPresetCount () const
	Return the number of standard configuration presets that this sound filter has. More...

virtual Bool	getPreset (Index presetIndex, FilterPreset &preset) const
	Get the standard preset for this sound filter with the specified index. More...

Bool	getIsSynchronized () const
	Return whether or not this sound filter performs thread synchronization. More...

void	setIsSynchronized (Bool newIsSynchronized)
	Set whether or not this sound filter performs thread synchronization. More...

Static Public Attributes
static const UTF8String	NAME
	A string indicating the human-readable name of this expander. More...

static const UTF8String	MANUFACTURER
	A string indicating the manufacturer name of this expander. More...

static const FilterVersion	VERSION
	An object indicating the version of this expander. More...

Static Public Attributes inherited from om::sound::filters::SoundFilter
static const om::resources::ResourceType	RESOURCE_TYPE
	The resource type for a sound filter. More...

Additional Inherited Members
Static Public Member Functions inherited from om::sound::filters::SoundFilter
static Size	getMaximumNumberOfInputs ()
	Return the maximum number of audio inputs that a SoundFilter can support. More...

static Size	getMaximumNumberOfOutputs ()
	Return the maximum number of audio outputs that a SoundFilter can support. More...

static Size	getMaximumNumberOfMIDIInputs ()
	Return the maximum number of MIDI inputs that a SoundFilter can support. More...

static Size	getMaximumNumberOfMIDIOutputs ()
	Return the maximum number of MIDI outputs that a SoundFilter can support. More...

Protected Member Functions inherited from om::sound::filters::SoundFilter
	SoundFilter ()
	Create a new sound filter with 1 audio input and output, and no MIDI inputs or outputs. More...

	SoundFilter (Size numInputs, Size numOutputs)
	Create a new sound filter with the specified number of audio inputs and outputs. More...

	SoundFilter (Size numInputs, Size numOutputs, Size numMIDIInputs, Size numMIDIOutputs)
	Create a new sound filter with the specified number of audio inputs and outputs. More...

void	setInputCount (Size newNumInputs)
	Set the number of inputs that this filter should have. More...

void	setOutputCount (Size newNumOutputs)
	Set the number of outputs that this filter should have. More...

void	setMIDIInputCount (Size newNumMIDIInputs)
	Set the number of MIDI inputs that this filter should have. More...

void	setMIDIOutputCount (Size newNumMIDIOutputs)
	Set the number of MIDI outputs that this filter should have. More...

Bool	isFirstFrame () const
	Return whether or not the filter's next frame to be processed is also its first frame. More...

void	lockMutex () const
	Acquire a mutex which handles subclass rendering parameter synchronization. More...

void	unlockMutex () const
	Release a mutex which handles subclass rendering parameter synchronization. More...

Detailed Description

A class that reduces the level of sound that is below a certain threshold.

This expander class uses peak sensing to determine an envelope level at each sample. If the envelope is below a user-defined threshold, the expander applies gain reduction to the sound at the expander's logarithmic compression ratio. The expander also has a variable-hardness knee which allows the user to smooth the transition from gain reduction to no gain reduction.

This expander can also be used as a true noise gate by setting the ratio to be equal to positive infinity.

Constructor & Destructor Documentation

om::sound::filters::Expander::Expander ( )

Create a new expander with the default compression parameters.

These are - threshold: -6dB, ratio: 2:1, knee: 0dB, attack: 2ms, hold: 100ms, release: 300ms, with unlinked channels.

om::sound::filters::Expander::Expander	(	Gain	threshold,
		Float	ratio,
		Float	attack,
		Float	hold,
		Float	release
	)

Create a new expander with specified threshold, ratio, attack, hold, and release.

This expander uses peak-sensing detection and has unlinked channels. The expander has the default knee of 0dB. All gain and threshold values are specified on a linear scale. The attack, hold, and release times are specified in seconds.

Member Function Documentation

Gain om::sound::filters::Expander::getThreshold ( ) const

inline

Return the linear full-scale value below which the expander applies gain reduction.

Gain om::sound::filters::Expander::getThresholdDB ( ) const

inline

Return the logarithmic full-scale value below which the expander applies gain reduction.

void om::sound::filters::Expander::setThreshold ( Gain newThreshold )

inline

Set the linear full-scale value below which the expander applies gain reduction.

The value is clamped to the valid range of [0,infinity] before being stored.

void om::sound::filters::Expander::setThresholdDB ( Gain newThresholdDB )

inline

Set the logarithmic full-scale value below which the expander applies gain reduction.

Float om::sound::filters::Expander::getRatio ( ) const

inline

Return the downward expansion ratio that the expander is using.

This value is expressed as a ratio of input to output gain below the compression threshold, expressed in decibels. For instance, a ratio of 2 indicates that for ever 1 decibels that the signal is below the threshold, the output signal will be attenuated by 2 dB. Thus, higher ratios indicate more extreme expansion. A ratio of +infinity is equivalent to a hard noise gate.

void om::sound::filters::Expander::setRatio ( Float newRatio )

inline

Set the downward expansion ratio that the expander is using.

This value is expressed as a ratio of input to output gain below the compression threshold, expressed in decibels. For instance, a ratio of 2 indicates that for ever 1 decibels that the signal is below the threshold, the output signal will be attenuated by 2 dB. Thus, higher ratios indicate more extreme expansion. A ratio of +infinity is equivalent to a hard noise gate.

The new ratio is clamped to the range of [1,100].

Gain om::sound::filters::Expander::getKnee ( ) const

inline

Return the knee radius of this expander in decibels.

This is the amount above the expander's threshold at which the expander first starts reducing level, as well as the amount below the expander's threshold where the actual expander ratio starts to be used. A higher knee will result it an expander that starts to apply gain reduction to envelopes that approach the threshold, resulting in a smoother transition from no gain reduction to full gain reduction.

void om::sound::filters::Expander::setKnee ( Gain newKnee )

inline

Set the knee radius of this expander in decibels.

This is the amount above the expander's threshold at which the expander first starts reducing level, as well as the amount below the expander's threshold where the actual expander ratio starts to be used. A higher knee will result it an expander that starts to apply gain reduction to envelopes that approach the threshold, resulting in a smoother transition from no gain reduction to full gain reduction.

The new knee value is clamped to the valid range of [0,+infinity].

Float om::sound::filters::Expander::getAttack ( ) const

inline

Return the attack of this expander in seconds.

This value indicates the time in seconds that it takes for the expander's detection envelope to respond to a sudden increase in signal level. Thus, a very small attack softens transients more than a slower attack which lets the transients through the expander.

void om::sound::filters::Expander::setAttack ( Float newAttack )

inline

Set the attack of this expander in seconds.

This value indicates the time in seconds that it takes for the expander's detection envelope to respond to a sudden increase in signal level. Thus, a very small attack softens transients more than a slower attack which lets the transients through the expander.

The new attack value is clamped to the range of [0,+infinity].

Float om::sound::filters::Expander::getHold ( ) const

inline

Return the hold time of this expander in seconds.

This value indicates the time in seconds that it takes for the expander's detection envelope to start responding to a sudden decrease in signal level. Thus, the hold time is a window after an initial transient in which the expander's envelope doesn't decrease, resulting in no further gain reduction until the hold time is expired, at which time the envelope release begins.

void om::sound::filters::Expander::setHold ( Float newHold )

inline

Set the hold time of this expander in seconds.

This value indicates the time in seconds that it takes for the expander's detection envelope to start responding to a sudden decrease in signal level. Thus, the hold time is a window after an initial transient in which the expander's envelope doesn't decrease, resulting in no further gain reduction until the hold time is expired, at which time the envelope release begins.

The new hold value is clamped to the range of [0,+infinity].

Float om::sound::filters::Expander::getRelease ( ) const

inline

Return the release of this expander in seconds.

This value indicates the time in seconds that it takes for the expander's detection envelope to respond to a sudden decrease in signal level. Thus, a very short release doesn't compress the signal after a transient for as long as a longer release. Beware, very short release times (< 5ms) can result in audible distortion.

void om::sound::filters::Expander::setRelease ( Float newRelease )

inline

Set the release of this expander in seconds.

This value indicates the time in seconds that it takes for the expander's detection envelope to respond to a sudden decrease in signal level. Thus, a very short release doesn't compress the signal after a transient for as long as a longer release. Beware, very short release times (< 5ms) can result in audible distortion.

The new release value is clamped to the valid range of [0,+infinity].

Bool om::sound::filters::Expander::getChannelsAreLinked ( ) const

inline

Return whether or not all channels in the expander are linked together.

If the value is TRUE, all channels are reduced by the maximum amount selected from all channel envelopes. This allows the expander to maintain the stereo image of the audio when expanding hard-panned sounds.

void om::sound::filters::Expander::setChannelsAreLinked ( Bool newChannelsAreLinked )

inline

Set whether or not all channels in the expander are linked together.

If the value is TRUE, all channels are reduced by the maximum amount selected from all channel envelopes. This allows the expander to maintain the stereo image of the audio when expanding hard-panned sounds.

Gain om::sound::filters::Expander::getGainReductionDB ( ) const

inline

Return the current gain reduction of the expander in decibels.

This value can be used as a way for humans to visualize how much the expander is reducing the signal at any given time.

Gain om::sound::filters::Expander::getGainReduction ( ) const

inline

Return the current gain reduction of the expander on a linear scale.

This value can be used as a way for humans to visualize how much the expander is reducing the signal at any given time.

Gain om::sound::filters::Expander::evaluateTransferFunction ( Gain input ) const

Evaluate the transfer function of the expander for an envelope with the specified amplitude.

Gain om::sound::filters::Expander::evaluateTransferFunctionDB ( Gain input ) const

inline

Evaluate the transfer function of the expander for an envelope with the specified amplitude in decibels.

virtual UTF8String om::sound::filters::Expander::getInputName ( Index inputIndex ) const

virtual

Return a human-readable name of the expander input at the specified index.

The expander has 2 inputs:

0: the expander's main input, the source of the signal that is going to be expanded.
1: the expander's sidechain input, the main input is expanded using this input if provided.

The main input's name is "Main Input", while the sidechain's name is "Sidechain".

Reimplemented from om::sound::filters::SoundFilter.

virtual UTF8String om::sound::filters::Expander::getName ( ) const

virtual

Return a human-readable name for this expander.

The method returns the string "Expander".

Reimplemented from om::sound::filters::SoundFilter.

virtual UTF8String om::sound::filters::Expander::getManufacturer ( ) const

virtual

Return the manufacturer name of this expander.

The method returns the string "Om Sound".

Reimplemented from om::sound::filters::SoundFilter.