Tsotsos. Hand Gesture Recognition within a Linguistics-Based Framework

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HandGestureRecognitionwithinaLinguistics-Based

Framework

KonstantinosG.Derpanis,RichardP.Wildes,andJohnK.Tsotsos

YorkUniversity,DepartmentofComputerScienceandCentreforVisionResearch(CVR)TorontoOnt.M3J1P3,Canada{kosta,wildes,tsostos}@cs.yorku.caWWWhomepage:http://cs.yorku.ca/˜{kosta,wildes,tsotsos}

Abstract

Anapproachtorecognizinghumanhandgesturesfromamonoculartemporalsequence

ofimagesispresented.Ofparticularconcernistherepresentationandrecognitionof

handmovementsthatareusedinsinglehandedAmericanSignLanguage(ASL).The

approachexploitspreviouslinguisticanalysisofmanuallanguagesthatdecomposedy-

namicgesturesintotheirstaticanddynamiccomponents.Thefirstlevelofdecompo-

sitionisintermsofthreesetsofprimitives,handshape,locationandmovement.Fur-

therlevelsofdecompositioninvolvethelexicalandsentencelevelsandarepartofour

planforfuturework.Weproposeandsubsequentlydemonstratethatgivenamonocular

gesturesequence,kinematicfeaturescanberecoveredfromtheapparentmotionthat

providedistinctivesignaturesfor14primitivemovementsofASL.Theapproachhas

beenimplementedinsoftwareandevaluatedonadatabaseof592gesturesequences

withanoverallrecognitionrateof86.00%forfullyautomatedprocessingand97.13%

formanuallyinitializedprocessing.

1Introduction

1.1Motivation

Interestinautomatedgesturerecognitionhasthepotentialtocreatepowerfulhuman

computerinterfaces.Computervisionprovidesmethodstoacquireandinterpretgesture

informationwhilebeingminimallyobtrusivetotheparticipant.Tobeuseful,methods

mustbeaccurateinrecognitionwithrapidexecutiontosupportnaturalinteraction.

Further,scalabilitytoencompassthelargerangeofhumangesturesisimportant.

Thecurrentpaperpresentsanapproachtorecognizinghumangesturesthatlever-

agesbothlinguistictheoryandcomputervisionmethods.Followingapathtakenin

thespeechrecognitioncommunityfortheinterpretationofspeech[22],weappealto

linguisticstodefineafinitesetofcontrastiveprimitives,termedphonemes,thatcan

becombinedtorepresentanarbitrarynumberofgestures.Thisensuresthatthedevel-

opedapproachisscalable.Currently,wearefocusedontherepresentationandrecovery

ofthemovementprimitivesderivedfromAmericanSignLanguage(ASL).Thissame2KonstantinosG.Derpanisetal.

linguisticsanalysishasalsobeenappliedtootherhandgesturelanguages(e.g.French

SignLanguage).Toaffecttherecoveryoftheseprimitives,wemakeuseofrobust,para-

metricmotionestimationtechniquestoextractsignaturesthatuniquelyidentifyeach

movementfromamonocularinputvideosequence.Here,itisinterestingtonotethat

humanobserversarecapableofrecoveringtheprimitivemovementsofASLbasedon

motioninformationalone[21].Forourcase,empiricalevaluationsuggeststhatalgo-

rithmicinstantiationoftheseideashassufficientaccuracytodistinguishthetargetset

ofASLmovementprimitives,withmodestprocessingpower.

1.2Relatedresearch

Significanteffortincomputervisionhasbeenmarshalledintheinvestigationofhuman

gesturerecognition(see[1,20]forgeneralreviews);someexamplesfollow.State-space

modelshavebeenusedtocapturethesequentialnatureofgesturesbyrequiringthata

seriesofstatesestimatedfromvisualdatamustmatchinsequence,toalearnedmodel

oforderedstates[7].Thisgeneralapproachalsohasbeenusedinconjunctionwith

parametriccurvilinearmodelsofmotiontrajectories[6].Analternativeapproachhas

usedstatisticalfactoredsamplinginconjunctionwithamodelofparameterizedgestures

forrecognition[5];thisapproachcanbeseenasanapplicationandextensionofthe

CONDENSATIONapproachtovisualtracking[14].Further,severalapproacheshave

usedHiddenMarkovModels(HMMs)[24,26,17],neuralnetworks[10]ortime-delay

neuralnetworks[31]tolearnfromtrainingexamples(e.g.,basedon2Dor3Dfeatures

extractedfromrawdata)andsubsequentlyrecognizegesturesinnovelinput.

Anumberofthecitedapproacheshaveachievedinterestingrecognitionrates,albeit

oftenwithlimitedvocabularies.Interestingly,manyoftheseapproachesanalyzeges-

tureswithoutbreakingthemintotheirconstituentprimitives,whichcouldbeusedasin

ourapproach,torepresentalargevocabularyfromasmallsetofgenerativeelements.

Instead,gesturesaredealtwithaswholes,withparameterslearnedfromtrainingsets.

Thistackmaylimittheabilityofsuchapproachestogeneralizetolargevocabularies

asthetrainingtaskbecomesinordinatelydifficult.Additionally,severaloftheseap-

proachesmakeuseofspecialpurposedevices(e.g.,colouredmarkers,datagloves)to

assistindataacquisition.

In[2,28],twooftheearliesteffortsofusinglinguisticconceptsforthedescription

andrecognitionofbothgeneralanddomainspecificmotionarepresented.Recently,

atleasttwolinesofinvestigationshaveappealedtolinguistictheoryasanattackon

issuesinscalinggesturerecognitiontosizablevocabularies[18,30].In[18]theauthors

usedatagloveoutputastheinputtotheirsystem.Eachphoneme,fromtheparameters

shape,location,orientationandmovement,ismodelledbyanHMMbasedonfeatures