net.sf.jaer.eventprocessing.filter
Class HarmonicFilter

java.lang.Object
  net.sf.jaer.eventprocessing.EventFilter
      net.sf.jaer.eventprocessing.EventFilter2D
          net.sf.jaer.eventprocessing.filter.HarmonicFilter

All Implemented Interfaces:

java.util.Observer

public class HarmonicFilter
extends EventFilter2D
implements java.util.Observer

An AE filter that filters out boring events caused by global flickering illumination. This filter measures the global event activity to obtain the phase and amplitude of flicker. If the amplitude exceeds a threashold, then events around the peak activity are filtered away. The phase and amplitude are computed by one of two methods.

The first uses a global harmonic oscillator with adjustable resonant frequency (set by user to double line frequency) and adjustable quality factor Q. This resonator is driven by ON and OFF events in opposite directions. It resonates with a phase such that it crosses zero at the peak of ON and OFF activities. During a zero crossing, events are filtered away.

The second method (planned, not yet implemented) histograms events into a cyclic histogram whose period is set as a parameter (e.g. 10 ms for 50 Hz illumination with line doubling). The histogram peaks tell the filter where to reject events. The histogram is forgotten slowly by periodically decaying all values. This method is not as physical and introduces a kind of 'frame' for forgetting, but it is slightly cheaper to compute.

Author:

tobi

Nested Class Summary

class

HarmonicFilter.HarmonicOscillator

Field Summary

Fields inherited from class net.sf.jaer.eventprocessing.EventFilter2D

enclosedFilter, out

Fields inherited from class net.sf.jaer.eventprocessing.EventFilter

annotationEnabled, chip, enclosedFilterChain, filterEnabled, log, perf, propertyTooltipMap, support

Constructor Summary

HarmonicFilter(AEChip chip)

Method Summary

EventPacket	filterPacket(EventPacket in) Subclasses implement this method to define custom processing.
static java.lang.String	getDescription()
java.lang.Object	getFilterState() returns array of last event times, x,y,type,[t0,t1], where t0/t1 are the last two event times, t0 first.
float	getFreq()
float	getQuality()
float	getThreshold()
void	initFilter() this should allocate and initialize memory: it may be called when the chip e.g.
boolean	isGeneratingFilter()
boolean	isPrintStats()
void	resetFilter() should reset the filter to initial state
void	setFilterEnabled(boolean yes) Resets the filter
void	setFreq(float f)
void	setPrintStats(boolean printStats)
void	setQuality(float q)
void	setThreshold(float threshold)
void	update(java.util.Observable o, java.lang.Object arg)

Methods inherited from class net.sf.jaer.eventprocessing.EventFilter2D

checkOutputPacketEventType, checkOutputPacketEventType, getEnclosedFilter, resetOut, setEnclosedFilter

Methods inherited from class net.sf.jaer.eventprocessing.EventFilter

getChip, getEnclosedFilterChain, getEnclosingFilter, getPrefs, getPropertyChangeSupport, getPropertyTooltip, isAnnotationEnabled, isEnclosed, isFilterEnabled, prefsEnabledKey, setAnnotationEnabled, setChip, setEnclosed, setEnclosedFilter, setEnclosedFilterChain, setEnclosingFilter, setPreferredEnabledState, setPrefs, setPropertyTooltip

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

HarmonicFilter

public HarmonicFilter(AEChip chip)

Method Detail

getDescription

public static java.lang.String getDescription()

isGeneratingFilter

public boolean isGeneratingFilter()

setFilterEnabled

public void setFilterEnabled(boolean yes)

Description copied from class: EventFilter2D

Resets the filter

Overrides:

setFilterEnabled in class EventFilter2D

Parameters:

yes - true to reset

See Also:

EventFilter.setPreferredEnabledState()

getFilterState

public java.lang.Object getFilterState()

returns array of last event times, x,y,type,[t0,t1], where t0/t1 are the last two event times, t0 first.

Specified by:

getFilterState in class EventFilter

resetFilter

public void resetFilter()

Description copied from class: EventFilter

should reset the filter to initial state

Specified by:

resetFilter in class EventFilter

update

public void update(java.util.Observable o,
                   java.lang.Object arg)

Specified by:

update in interface java.util.Observer

initFilter

public void initFilter()

Description copied from class: EventFilter

this should allocate and initialize memory: it may be called when the chip e.g. size parameters are changed after creation of the filter

Specified by:

initFilter in class EventFilter

getThreshold

public float getThreshold()

setThreshold

public void setThreshold(float threshold)

getQuality

public float getQuality()

setQuality

public void setQuality(float q)

getFreq

public float getFreq()

setFreq

public void setFreq(float f)

isPrintStats

public boolean isPrintStats()

setPrintStats

public void setPrintStats(boolean printStats)

filterPacket

public EventPacket filterPacket(EventPacket in)

Description copied from class: EventFilter2D

Subclasses implement this method to define custom processing.

Specified by:

filterPacket in class EventFilter2D

Parameters:

in - the input packet

Returns:

the output packet