savingdengjiagui

DSPFUNTHEGUIWAYA.
Yardim,M.
A.
Mughal,G.
D.
CainandD.
BarjamovicUniversityofWestminster,DepartmentofElectronicSystems,LondonW1M8JS,UKABSTRACTProductionofGraphicalUserInterfaces(GUIs)hasbeenfoundtobeavitalingredientinbuildingupacomprehensiveMATLABframeworksupportingthelearning-andenjoyment-ofDSPtopics.
WedescribesomeofthefunctionalandestheticissuessurroundingthetwodozenGUIswehavedevelopedandusedtoanimatevariousDSPtopicsduringin-classdemonstrationsandinstudentlaboratories.
WeconcludethatthesubstantialdevelopmenteffortneededforareallygoodGUIispaidbackbytheimpactonlearningandtheenhancementofroutinedesignandmeasurementtasks.
MATLABissouseful,insomanyways,acrossabroadrangeofDSPlearningsituationsthatitiseasytohighlightmanyofitsstrengths.
Apartfromwidespreadusebyourresearchersastheireverydayconcept-provingtoolofchoice,ourmaininterestslieinundergraduatelearning(immediatelyuponentrytoYear1ofstudyandthenthroughoutthreeyearsofBEngwork),inMaster'sstudy,andalsoinContinuingProfessionalDevelopmentshortcoursesaimedatpracticingEngineers.
MATLABisanindispensableacceleratoroflearningandengineofproductivityenhancementateachoftheserungsofoureducationalladder.
ItisfortunateforDSPaficionadosthatoursubjectisinherentlySENSUAL,andthatwecansoreadilyconveyhigh-impactmessagesabouttheintricaciesofitsvarioussub-topicsbyappealingtoastudent'ssensesofsoundandvision.
Anoise-contaminatedsoundpassageplayedoutloudisguaranteedtoregisteritsundesirabilitymorecompellinglythanadrysignal-to-noiseequationorstarkgraph.
Evenbetter,thecollisionandadhesionoftwotonesleapingaboutinananimatedspectraldisplayevokesdynamismandexcitementonthepartofafledglingDSPengineerchargedwiththetaskofunravelingtheseinterferingsignals.
MATLABsuppliesaframeworkforreadilyenliveningtheseandclassroomdemonstrationandlaboratoryscenariossopowerfullythatmodernteachingofDSPneednolongersufferunderthedrymathematicalimagewhichusedtounsettlenewcomerstothefield.
WetrytoinsistthatthelearningofDSPbemadeFUN.
Inpursuitofthis,weuseMATLABinthesevariousclassroomroles:"Scratch-pad"trialofconceptsonthefly"PauseStories"forautomated,pre-cannedexpositions(ina"slideshow"vein)"Sound-filehacking"togainaquickfeelforprocessingeffectsM-filecreationforsmalltasksolutionSeriousm-fileutilityconstructiontoaugmentToolboxfeatures"ControlPanel"GUItoolcreationforrepetitiveuseTheseusagestylesareinincreasingorderofsophisticationandinvestmentonthepartofacademicandsupportstaff.
Thefirsttwoareinexpensive,butoftenaddspontaneityalongstructuredlinesofexposition.
Thingsstartgettingespeciallyinterestingwith"sound-filehacking".
Thiscodefragment:[x,fs]=wavread('terminat.
wav');y=[x;flipud(x)];plot(y);sound(y,fs)iseasyforstudentsinaPC-equippedlectureroomtoquicklyinputandgrasp,yetneverfailstodeliverafewwarmchucklesofamusement.
Thefinalthreeusesincurescalatingeffortandseriousness,butdeliverfargreaterlearningbenefits.
Thedeveloperineachcasemightalsobethestudent(andcertainlyinthehomeworkandprojectassignmentsituationthatoftenhappens);moreoften,dedicatedacademiceffortbehindthesceneshasbeendeployedandthestudentisinthehappypositionofsimply"riding"onwhatgetsprovided.
Slick,labour-savingspecialistm-filescanbepressedintoservicesothatstudentscanfocusongraspingtheconcepts,notstumblingoverthetools.
Notwithstandingthebesteffortsofthedevelopmentteam(buildingonthegreattransparencyandself-documentingsimplicityMATLABbringstothepartyanyway),wehavefrequentlybeenastonishedtofindvery,veryslowratesofcodedevelopmentinabbreviatedin-classjobsoreven3-hourlaboratorysessions.
Somestudentssimplycannotamalgamatehigh-levelconceptsandsimplecodingtodousefulworkunderpressureoftime.
Accelerationofsignalhandlingisamust.
HenceourenthusiasmforGraphicalUserInterfaces(GUIs).
GUIsaregreatforsetpiece,repetitivetasks.
Weliketoviewthemaslow-costitemsofdedicated,powerfulDSPinstrumentation:"controlpanels"forunleashingmagic.
OurGUIproductioneffortshavebeendirectedbothatin-classdemonstrationofconceptsformakinglectureslivelyandatclosesupportofdesignandmeasurement.
Thefirstusagehasbeeneffectivewherecomplexsignalshavetobevisualized,wherez-planetopologyneedstobeseen,wherepole/zerogeometriesrequirecrystallization,wheresurveyingfilterbankoutputscanilluminatethesignalprocessinglandscape,etc.
WefindithandytohaveasmallselectortoolbarvisibleforeasilyinvokingthecoupleofdozenGUIswetendtouseroutinely.
Thisarrangement(seenintherightcornerofFigure1)givesbothanalphabeticorderingandvisualcuestothelecturer(whomaybehard-pressedtorecallthenameoftheintendeddemo).
Figure1alsoexhibitstheresultofacoupleofselections;partiallycoveredisa3-d"corkscrew"depictionofcomplexexponentialsignalswhichhasbeenimmenselyhelpfulinassertingtherealityofourmostimportantcomplexsignals.
AlsoinFigure1isslifer-oneofourmostpopulartoolsforhandcrafteddigitalfilterdesign,permittinghighlyresponsiveadjustmentofindividualcoefficientvalues(hereofadigitaldifferentiator),variationofFrequencySamplingtransferfunctionvaluesandevennon-equispacedspectralmanipulationwhichMATLAB'sfasthandlingofVandermondematrixinversioncausestolookeffortless.
Figure1.
ASmallCollageofOurGUIsFigure2showsaviewofthez-planerarelyseenbystudentselsewhere.
HerewehavetakentheusualMATLABcoefficientvectorstobea=[10.
6]andb=ones(1,5).
Thestudentisabletohorizontallyslicethez-functionfinelyenoughtoscrutinizethesurfaceperturbationcausedbythepoleonthenegativerealz-axiswhilealsoseeingtheDFTevaluationsshownaroundtheunitcirclebyastemplot.
Asdifferentpoleandzerocontributionsareimportedthestudentisabletoobservetheundulationscausedinthezsurfaceandhowthesearemanifested"attheedge",wheretheDFTofthetransferfunctionresides.
Suchpotentandusabletoolsinspirebothconfidenceinthetheoreticalideasanddeliverpracticaloutcomesformeetingtoughdesignspecs.
Studentsreactextremelywelltothesolidityandreliabilitythattoolssuchastheserepresent.
Figure2.
Circular-SlicingaZ-TransformButcanweexpectstudentstodesigngoodGUIsCertainlysuchanaspirationissmackontargetformoderngroupwork-intensive,creativestudent-ledengineeringlearning.
Yetourexperienceismixed;severalindividualprojectshaveproducedsuperb,highlyusefulGUIsthathavegoneontobecomepermanentfixturesinourtoolscape.
Butmanyhavebeenfeeble,painfulexercisestoo.
Fartoooftenstudentshavedifficultyarticulatingandthenimplementingfeatureswhicharetrulyuseful.
ThewholeprocessiscomplicatedbytheinherentdifficultyofstructuringaGUI.
Theexposuretoswitchyardprogrammingisveryeducational,butthemechanicsofcallbacksandponderoussyntaxarenoteasytomasterforbeginners.
BraveattemptslikeMATHWORKS'"Guide"arenotyetabletosimplifydevelopmentsufficiently.
Atthepresenttime,youhavetoreallywanttobuildaGUIifit'sgoingtobemuchofasuccess.
IndevelopingourGUIoutlookforlearningaids,weweregreatlyinfluencedbyMATLAB'sdemosigdemo2,whichiswonderfullyeconomical,self-explanatoryanduseful.
Thisoneexampleimmediatelysuggestsahostoftransformillustratorsthatcouldprovidegoodinsightforstudents;nolongerisitnecessaryfortransformtabulationstobesodryanduninspiring.
Wecreateda"HilbertTransformTour"whichbothdrawstogetheranumberoftheseelusive,unrulytransformpairs(astime-domainequations),andalsoanimatesthemsothatthebrowsingstudentcan,underslidercontrol,easilymodifysignalparametersandappreciatechangingpatternsandinteractions(especiallyasmanifestedinanalyticsignals).
Filterdesignalsofurnishesawealthofopportunitiesforanimation,displayandmeasurementGUIs.
MATLAB'sfiltdemoisa(hard-hitting)caseinpoint.
Wehavesometimesfounditusefulto"soupup"suchnicedemosthroughsmallmodificationsthataddsensualimpact(say,byincorporatingmusicprocessing).
Andwecangodeep,toinspecttheiteration-by-iterationmechanicsoffilterdesignalgorithms.
Suchiterativeminutiaecanbefascinatingtowatch,whilealsoleavingthestudentwithafeelingoftheprecariousnessofiteration(especiallywhenconvergencefailstohappen)andthepotencyofclosed-formsolutionsandmatrixformulations.
Manyinstrumentationtaskscryoutforpurpose-builtGUIs.
Thisisespeciallytrueintheareaofrandomsignalmeasurement,anarenanotoriousforrequiringgiganticrecordlength/ensemblesizes(tenstohundredsofthousandsofsamples)beforeanytextbookfindingscanbevalidatedconvincingly.
Hererepetitivemechanization(andsomesortofaveraging)ofrandomsignalrealizationsisthefocus.
Sofarwehaveattackedthistopiconlybym-fileutilities;itisoneofournexttargetsforGUIdevelopment.
WhatfeaturesshouldagoodGUIexhibitWethinkthattheenvelopeoffunctionalityshouldberestricted,andobvioustotheuser.
ExcessivecomprehensivenessleadstoalumberingGUIthatisneitherfishnorfowl(andgreatlyextendsitsdevelopmentschedule).
Itscontrolsandlayoutshouldbefriendlyandinviting,withbalanceandharmonyuppermost.
Spaciousnessofuicontrolobjectdeploymentisalwayshardtoachieve,andmayrequiredeeper"parking"(intomenuitems,dialogboxesorpopupmenus)thantheGUIdeveloperwouldlike.
Theusershouldonlyrarelybecalledontohavetopushfurtherdownthan3levelsofinteractionhierarchy(i.
e.
,2buttonclicks).
AusershouldfeelthepoweroftheGUI'soperation,andbreatheasighofreliefatnothavingtogetdowntothenitty-grittyofdoingthemainunderlyingcodingpersonally.
AnyGUIthat'shardtolearntodrivewillsimplybeabandonedinfavouroftheeaseofDIYthatMATLABalwaysholdsouttousers(particularlythosewhohavebuiltupapotentandfamiliarsuiteofspecialistm-fileutilities).
AnyGUIthatismysterious,illogical,unreliableandburdensometonavigatewillincurneedlessOperatorFatigueandwillbreednotjustdisdain-butactivehatred.
Again,suchafailedGUIisheadedforthescrapheap.
WethinkthatGUIscomein"threetimeflavours":thosethataredevelopedin3minutes,3daysor3months.
The3-minutequickiecanonlybesomethingsimplelikeaddingaslidertofigurewindowtofacilitateobservationofparameterchangeeffects,addingapushbuttontoinvokesoundsorflashcolourchanges,andsoforth.
Suchlimitedaspirationsalmostalwayspaybacktheeffortadequately.
Attheotherextreme,reallyambitiousandpolishedGUIgoalscaneasilytake3monthsormore.
OurexperienceisthattheseverycomprehensiveGUIsaredauntingevenforveteranGUImakersanddegenerateintointricateinteractionsofcontrolconditionsthatcanbehardtojustifyconsistently,muchlesstorememberformaintenanceandupgrading.
Ourfavouritecategoryisthe3-daytypeofGUI.
Herethemindsetislimitedtospecifichorizonswhichoftenproveachievable.
OurbestGUIsareupandrunning(asregardstheiressentialfeatures)veryrapidly.
Subsequentfine-tuningandconsideredextensionmakegoonovermanymonths,ofcourse,butthefactremainsthatitwasa3-dayconcept,itgaveatleastalimiteddegreeofserviceinabout3days,anditbenefitedfromveryearlyuserfeedback.
Throughouttheprocess,sketching-andre-sketching-thecontrolpanellayoutbeforeinvestingincodingprovestobeakeyfactorinhomingintoagoodGUI.
Figure3showsdemoleak-thefirstGUItoemergefromourgroup.
ThisprovidedourfirstviewofthedynamiceffectsofleakageinspectralanalysisasatonewasforcedofftheDFTgridpoints,andstillprovidesimpressivetestimonytothepotencyofwindowing.
Figure3.
ADynamicSpectralAnalysisGUIWherethenisthe"fun"inallthisThereisnodoubtthatitistheendusers(andnottheharassedGUIdevelopers)whichstandtohavethebulkofthefun.
Theyhavebuttotestdrivethefinalproduct.
Ourfinaljudgementisunequivocal:agoodGUIisapowerfulaidinbreakingdownresistancetothemathematicalmatterswhichunderpinDSP.
AreasonablygoodGUIisprettyeasytoachieve;agreatGUIisrare,butpropelsitsusertoastateofDSP-joy.
ACKNOWLEDGEMENTWearegratefulforthegoodprogrammingstyleandcreativeenergythatDr.
GregAllenofJamesCookUniversity-fatherofdemoleakandmuchmore-broughttoourGUIfactory.