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