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<div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6258e36bbe9ad24cfaacba87/bg1.jpg"><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">Object<span class="_"> </span>T<span class="_ _0"></span>racking:<span class="_"> </span>A<span class="_"> </span>Surve<span class="_ _1"></span>y</div><div class="t m0 x1 h3 y2 ff2 fs1 fc0 sc0 ls0 ws0">Alper<span class="_ _2"> </span>Yilmaz</div><div class="t m0 x1 h4 y3 ff3 fs2 fc0 sc0 ls0 ws0">Ohio<span class="_"> </span>State<span class="_"> </span>University</div><div class="t m0 x1 h3 y4 ff2 fs1 fc0 sc0 ls0 ws0">Omar<span class="_ _2"> </span>Ja<span class="_ _1"></span>v<span class="_ _1"></span>ed</div><div class="t m0 x1 h4 y5 ff3 fs2 fc0 sc0 ls0 ws0">ObjectV<span class="_ _1"></span>ideo<span class="_ _1"></span>,<span class="_"> </span>Inc<span class="_ _3"></span>.</div><div class="t m0 x1 h3 y6 ff2 fs1 fc0 sc0 ls0 ws0">and</div><div class="t m0 x1 h3 y7 ff2 fs1 fc0 sc0 ls0 ws0">Mubarak<span class="_ _2"> </span>Shah</div><div class="t m0 x1 h4 y8 ff3 fs2 fc0 sc0 ls0 ws0">University<span class="_"> </span>of<span class="_"> </span>Central<span class="_"> </span>Florida</div><div class="t m0 x1 h5 y9 ff4 fs2 fc0 sc0 ls0 ws0">The<span class="_ _2"> </span>goal<span class="_"> </span>of<span class="_ _2"> </span>this<span class="_"> </span>article<span class="_ _2"> </span>is<span class="_"> </span>to<span class="_ _2"> </span>review<span class="_ _4"> </span>the<span class="_ _4"> </span>state-of-the-art<span class="_ _4"> </span>tracking<span class="_ _4"> </span>methods,<span class="_"> </span>classify<span class="_ _4"> </span>them<span class="_ _2"> </span>into<span class="_ _4"> </span>different<span class="_ _4"> </span>cate-</div><div class="t m0 x1 h5 ya ff4 fs2 fc0 sc0 ls0 ws0">gories,<span class="_ _5"> </span>and<span class="_ _5"> </span>identify<span class="_"> </span>new<span class="_ _5"> </span>trends.<span class="_ _5"> </span>Object<span class="_"> </span>tracking<span class="_ _3"></span>,<span class="_"> </span>in<span class="_ _5"> </span>general,<span class="_"> </span>is<span class="_ _5"> </span>a<span class="_"> </span>challenging<span class="_ _5"> </span>problem.<span class="_ _5"> </span>Difficulties<span class="_"> </span>in<span class="_ _5"> </span>tracking</div><div class="t m0 x1 h5 yb ff4 fs2 fc0 sc0 ls0 ws0">objects<span class="_ _5"> </span>can<span class="_"> </span>arise<span class="_ _5"> </span>due<span class="_ _5"> </span>to<span class="_"> </span>abrupt<span class="_ _5"> </span>object<span class="_ _5"> </span>motion,<span class="_"> </span>c<span class="_ _1"></span>hanging<span class="_ _5"> </span>appearance<span class="_"> </span>patterns<span class="_ _5"> </span>of<span class="_ _5"> </span>both<span class="_"> </span>the<span class="_ _5"> </span>object<span class="_ _5"> </span>and<span class="_"> </span>the<span class="_ _5"> </span>scene,</div><div class="t m0 x1 h5 yc ff4 fs2 fc0 sc0 ls0 ws0">nonrigid<span class="_ _2"> </span>object<span class="_ _6"> </span>structures,<span class="_ _4"> </span>object-to-object<span class="_ _6"> </span>and<span class="_ _2"> </span>object-to-scene<span class="_ _6"> </span>occlusions,<span class="_ _2"> </span>and<span class="_ _2"> </span>camera<span class="_ _2"> </span>motion.<span class="_ _6"> </span>Tracking<span class="_ _2"> </span>is</div><div class="t m0 x1 h5 yd ff4 fs2 fc0 sc0 ls0 ws0">usually<span class="_ _2"> </span>performed<span class="_ _4"> </span>in<span class="_ _2"> </span>the<span class="_ _2"> </span>context<span class="_ _2"> </span>of<span class="_ _2"> </span>higher-level<span class="_ _4"> </span>applications<span class="_ _2"> </span>that<span class="_ _2"> </span>require<span class="_ _2"> </span>the<span class="_ _2"> </span>location<span class="_ _2"> </span>and/or<span class="_ _2"> </span>shape<span class="_ _4"> </span>of<span class="_ _2"> </span>the</div><div class="t m0 x1 h5 ye ff4 fs2 fc0 sc0 ls0 ws0">object<span class="_ _4"> </span>in<span class="_ _4"> </span>every<span class="_ _4"> </span>frame.<span class="_ _4"> </span>Typically<span class="_ _0"></span>,<span class="_ _4"> </span>assumptions<span class="_ _2"> </span>are<span class="_ _4"> </span>made<span class="_ _4"> </span>to<span class="_ _4"> </span>constrain<span class="_ _2"> </span>the<span class="_ _4"> </span>tracking<span class="_ _4"> </span>problem<span class="_ _4"> </span>in<span class="_ _4"> </span>the<span class="_ _2"> </span>context<span class="_ _4"> </span>of</div><div class="t m0 x1 h5 yf ff4 fs2 fc0 sc0 ls0 ws0">a<span class="_ _2"> </span>particular<span class="_ _4"> </span>application.<span class="_ _2"> </span>In<span class="_ _2"> </span>this<span class="_ _2"> </span>survey<span class="_ _0"></span>,<span class="_ _2"> </span>we<span class="_ _2"> </span>categorize<span class="_ _2"> </span>the<span class="_ _2"> </span>tracking<span class="_ _4"> </span>methods<span class="_ _2"> </span>on<span class="_ _2"> </span>the<span class="_ _2"> </span>basis<span class="_ _2"> </span>of<span class="_ _2"> </span>the<span class="_ _2"> </span>object<span class="_ _2"> </span>and</div><div class="t m0 x1 h5 y10 ff4 fs2 fc0 sc0 ls0 ws0">motion<span class="_"> </span>representations<span class="_ _4"> </span>used,<span class="_"> </span>provide<span class="_ _4"> </span>detailed<span class="_"> </span>descriptions<span class="_ _4"> </span>of<span class="_"> </span>representative<span class="_ _4"> </span>methods<span class="_"> </span>in<span class="_ _4"> </span>each<span class="_"> </span>category<span class="_ _0"></span>,<span class="_"> </span>and</div><div class="t m0 x1 h5 y11 ff4 fs2 fc0 sc0 ls0 ws0">examine<span class="_ _5"> </span>their<span class="_"> </span>pros<span class="_ _5"> </span>and<span class="_ _5"> </span>cons.<span class="_ _5"> </span>Moreover<span class="_ _0"></span>,<span class="_ _5"> </span>we<span class="_"> </span>discuss<span class="_ _5"> </span>the<span class="_ _5"> </span>important<span class="_ _5"> </span>issues<span class="_"> </span>related<span class="_ _5"> </span>to<span class="_ _5"> </span>tracking<span class="_ _5"> </span>including<span class="_"> </span>the<span class="_ _5"> </span>use</div><div class="t m0 x1 h5 y12 ff4 fs2 fc0 sc0 ls0 ws0">of<span class="_"> </span>appropriate<span class="_"> </span>image<span class="_"> </span>features,<span class="_"> </span>selection<span class="_"> </span>of<span class="_"> </span>motion<span class="_"> </span>models<span class="_ _3"></span>,<span class="_"> </span>and<span class="_"> </span>detection<span class="_"> </span>of<span class="_"> </span>objects.</div><div class="t m0 x1 h5 y13 ff4 fs2 fc0 sc0 ls0 ws0">Categories<span class="_ _4"> </span>and<span class="_ _2"> </span>Subject<span class="_ _2"> </span>Descriptors:<span class="_ _2"> </span>I.4.8<span class="_ _2"> </span>[<span class="ff5">Image<span class="_ _2"> </span>Processing<span class="_ _2"> </span>and<span class="_ _2"> </span>Computer<span class="_ _2"> </span>Vision</span>]:<span class="_ _4"> </span>Scene<span class="_ _2"> </span>Analysis—</div><div class="t m0 x1 h4 y14 ff3 fs2 fc0 sc0 ls0 ws0">T<span class="_ _3"></span>racking</div><div class="t m0 x1 h5 y15 ff4 fs2 fc0 sc0 ls0 ws0">General<span class="_"> </span>T<span class="_ _3"></span>erms:<span class="_"> </span>Algorithms</div><div class="t m0 x1 h5 y16 ff4 fs2 fc0 sc0 ls0 ws0">Additional<span class="_ _5"> </span>Key<span class="_ _7"> </span>W<span class="_ _3"></span>ords<span class="_ _5"> </span>and<span class="_ _7"> </span>Phrases:<span class="_ _7"> </span>Appearance<span class="_ _5"> </span>models,<span class="_ _7"> </span>contour<span class="_ _7"> </span>evolution,<span class="_ _7"> </span>feature<span class="_ _5"> </span>selection,<span class="_ _7"> </span>object<span class="_ _7"> </span>detection,</div><div class="t m0 x1 h5 y17 ff4 fs2 fc0 sc0 ls0 ws0">object<span class="_"> </span>representation,<span class="_"> </span>point<span class="_"> </span>tracking<span class="_ _1"></span>,<span class="_"> </span>shape<span class="_"> </span>tracking</div><div class="t m0 x1 h4 y18 ff5 fs2 fc0 sc0 ls0 ws0">ACM<span class="_"> </span>Reference<span class="_"> </span>F<span class="_ _1"></span>ormat:</div><div class="t m0 x1 h5 y19 ff4 fs2 fc0 sc0 ls0 ws0">Yilmaz,<span class="_ _4"> </span>A.,<span class="_ _4"> </span>Javed,<span class="_ _4"> </span>O.,<span class="_ _4"> </span>and<span class="_ _2"> </span>Shah,<span class="_ _4"> </span>M.<span class="_ _2"> </span>2006.<span class="_ _4"> </span>Object<span class="_ _2"> </span>tracking:<span class="_ _2"> </span>A<span class="_ _4"> </span>survey<span class="_ _0"></span>.<span class="_ _2"> </span><span class="ff3">ACM<span class="_ _4"> </span>Comput.<span class="_ _2"> </span>Surv<span class="_ _3"></span>.<span class="_ _4"> </span>38<span class="ff4">,<span class="_ _2"> </span>4,<span class="_ _2"> </span>Article<span class="_ _4"> </span>13</span></span></div><div class="t m0 x1 h5 y1a ff4 fs2 fc0 sc0 ls0 ws0">(Dec.<span class="_"> </span>2006),<span class="_"> </span>45<span class="_"> </span>pages<span class="_ _1"></span>.<span class="_"> </span>DOI<span class="_"> </span><span class="ff6">=<span class="_ _8"> </span></span>10.1145/1177352.1177355<span class="_ _9"> </span>http://doi.acm.org/10.1145/1177352.1177355</div><div class="t m0 x1 h5 y1b ff4 fs2 fc0 sc0 ls0 ws0">This<span class="_ _7"> </span>material<span class="_ _5"> </span>is<span class="_ _5"> </span>based<span class="_ _7"> </span>on<span class="_ _5"> </span>work<span class="_ _5"> </span>funded<span class="_ _7"> </span>in<span class="_ _5"> </span>part<span class="_ _7"> </span>by<span class="_ _5"> </span>the<span class="_ _5"> </span>US<span class="_ _7"> </span>Government.<span class="_ _5"> </span>Any<span class="_ _5"> </span>opinions<span class="_ _1"></span>,<span class="_ _5"> </span>findings<span class="_ _1"></span>,<span class="_ _7"> </span>and<span class="_ _5"> </span>conclusions</div><div class="t m0 x1 h5 y1c ff4 fs2 fc0 sc0 ls0 ws0">or<span class="_ _4"> </span>recommendations<span class="_ _2"> </span>expressed<span class="_ _2"> </span>in<span class="_ _2"> </span>this<span class="_ _2"> </span>material<span class="_ _4"> </span>are<span class="_ _2"> </span>those<span class="_ _2"> </span>of<span class="_ _2"> </span>the<span class="_ _4"> </span>authors<span class="_ _2"> </span>and<span class="_ _2"> </span>do<span class="_ _2"> </span>not<span class="_ _2"> </span>necessarily<span class="_ _4"> </span>reflect<span class="_ _2"> </span>the</div><div class="t m0 x1 h5 y1d ff4 fs2 fc0 sc0 ls0 ws0">views<span class="_"> </span>of<span class="_"> </span>the<span class="_"> </span>US<span class="_"> </span>Government.</div><div class="t m0 x1 h5 y1e ff4 fs2 fc0 sc0 ls0 ws0">Author’s<span class="_ _a"> </span>address:<span class="_ _a"> </span>A.<span class="_ _b"> </span>Yilmaz,<span class="_ _a"> </span>Department<span class="_ _b"> </span>of<span class="_ _a"> </span>CEEGS,<span class="_ _a"> </span>Ohio<span class="_ _a"> </span>State<span class="_ _b"> </span>University;<span class="_ _a"> </span>email:<span class="_ _b"> </span>yilmaz.15@osu.edu;</div><div class="t m0 x1 h5 y1f ff4 fs2 fc0 sc0 ls0 ws0">O<span class="_ _1"></span>.<span class="_ _6"> </span>Javed,<span class="_ _2"> </span>ObjectVideo,<span class="_ _2"> </span>Inc.,<span class="_ _2"> </span>Reston,<span class="_ _a"> </span>V<span class="_ _0"></span>A<span class="_ _6"> </span>20191;<span class="_ _6"> </span>email:<span class="_ _6"> </span>ojaved@objectvideo.com;<span class="_ _6"> </span>M.<span class="_ _6"> </span>Shah,<span class="_ _6"> </span>School<span class="_ _6"> </span>of<span class="_ _6"> </span>EECS,</div><div class="t m0 x1 h5 y20 ff4 fs2 fc0 sc0 ls0 ws0">University<span class="_"> </span>of<span class="_"> </span>Central<span class="_"> </span>Florida;<span class="_"> </span>email:<span class="_"> </span>shah@cs.ucf<span class="_ _3"></span>.edu.</div><div class="t m0 x1 h5 y21 ff4 fs2 fc0 sc0 ls0 ws0">P<span class="_ _1"></span>ermission<span class="_"> </span>to<span class="_"> </span>make<span class="_"> </span>digital<span class="_"> </span>or<span class="_"> </span>hard<span class="_ _5"> </span>copies<span class="_"> </span>of<span class="_"> </span>part<span class="_"> </span>or<span class="_"> </span>all<span class="_"> </span>of<span class="_"> </span>this<span class="_"> </span>work<span class="_"> </span>for<span class="_"> </span>personal<span class="_"> </span>or<span class="_ _5"> </span>classroom<span class="_"> </span>use<span class="_"> </span>is<span class="_"> </span>granted</div><div class="t m0 x1 h5 y22 ff4 fs2 fc0 sc0 ls0 ws0">without<span class="_ _7"> </span>fee<span class="_ _7"> </span>provided<span class="_ _7"> </span>that<span class="_ _7"> </span>copies<span class="_ _7"> </span>are<span class="_ _7"> </span>not<span class="_ _7"> </span>made<span class="_ _7"> </span>or<span class="_ _7"> </span>distributed<span class="_ _7"> </span>for<span class="_ _7"> </span>profit<span class="_ _7"> </span>or<span class="_ _7"> </span>direct<span class="_ _7"> </span>commercial<span class="_ _7"> </span>advantage<span class="_ _7"> </span>and<span class="_ _7"> </span>that</div><div class="t m0 x1 h5 y23 ff4 fs2 fc0 sc0 ls0 ws0">copies<span class="_"> </span>show<span class="_"> </span>this<span class="_"> </span>notice<span class="_ _5"> </span>on<span class="_"> </span>the<span class="_"> </span>first<span class="_"> </span>page<span class="_"> </span>or<span class="_"> </span>initial<span class="_"> </span>screen<span class="_ _5"> </span>of<span class="_"> </span>a<span class="_"> </span>display<span class="_"> </span>along<span class="_"> </span>with<span class="_"> </span>the<span class="_ _5"> </span>full<span class="_"> </span>citation.<span class="_"> </span>Copyrights</div><div class="t m0 x1 h5 y24 ff4 fs2 fc0 sc0 ls0 ws0">for<span class="_ _2"> </span>components<span class="_ _2"> </span>of<span class="_ _6"> </span>this<span class="_ _2"> </span>work<span class="_ _2"> </span>owned<span class="_ _6"> </span>by<span class="_ _2"> </span>others<span class="_ _2"> </span>than<span class="_ _2"> </span>ACM<span class="_ _6"> </span>must<span class="_ _2"> </span>be<span class="_ _2"> </span>honored.<span class="_ _6"> </span>Abstracting<span class="_ _2"> </span>with<span class="_ _2"> </span>credit<span class="_ _6"> </span>is<span class="_ _2"> </span>per-</div><div class="t m0 x1 h5 y25 ff4 fs2 fc0 sc0 ls0 ws0">mitted.<span class="_"> </span>To<span class="_"> </span>copy<span class="_ _4"> </span>otherwise,<span class="_"> </span>to<span class="_ _4"> </span>republish,<span class="_ _4"> </span>to<span class="_ _4"> </span>post<span class="_ _4"> </span>on<span class="_ _4"> </span>servers,<span class="_"> </span>to<span class="_ _4"> </span>redistribute<span class="_ _4"> </span>to<span class="_ _4"> </span>lists,<span class="_"> </span>or<span class="_ _4"> </span>to<span class="_ _4"> </span>use<span class="_ _4"> </span>any<span class="_ _4"> </span>component</div><div class="t m0 x1 h5 y26 ff4 fs2 fc0 sc0 ls0 ws0">of<span class="_ _2"> </span>this<span class="_ _2"> </span>work<span class="_ _2"> </span>in<span class="_ _2"> </span>other<span class="_ _2"> </span>works<span class="_ _2"> </span>requires<span class="_ _2"> </span>prior<span class="_ _2"> </span>specific<span class="_ _2"> </span>permission<span class="_ _2"> </span>and<span class="_ _c"></span>/or<span class="_ _2"> </span>a<span class="_ _2"> </span>fee.<span class="_ _4"> </span>Permissions<span class="_ _4"> </span>may<span class="_ _2"> </span>be<span class="_ _2"> </span>requested</div><div class="t m0 x1 h5 y27 ff4 fs2 fc0 sc0 ls0 ws0">from<span class="_"> </span>Publications<span class="_ _4"> </span>Dept.,<span class="_"> </span>ACM,<span class="_ _4"> </span>Inc.,<span class="_"> </span>2<span class="_ _4"> </span>Penn<span class="_"> </span>Plaza,<span class="_"> </span>Suite<span class="_"> </span>701,<span class="_ _4"> </span>New<span class="_ _4"> </span>Y<span class="_ _0"></span>ork,<span class="_ _4"> </span>NY<span class="_ _4"> </span>10121-0701<span class="_"> </span>USA,<span class="_ _4"> </span>fax<span class="_ _4"> </span><span class="ff6">+</span>1<span class="_"> </span>(212)</div><div class="t m0 x1 h5 y28 ff4 fs2 fc0 sc0 ls0 ws0">869-0481,<span class="_"> </span>or<span class="_"> </span>permissions@acm.org.</div><div class="t m0 x2 h5 y29 ff4 fs2 fc0 sc0 ls0 ws0">c</div><div class="t m0 x1 h5 y2a ff6 fs2 fc0 sc0 ls0 ws0"><span class="ff4">2006<span class="_ _a"> </span>ACM<span class="_ _a"> </span>0360-0300/2006/12-ART13<span class="_ _a"> </span>$5.00<span class="_ _a"> </span>DOI:<span class="_ _a"> </span>10.1145/1177352.1177355<span class="_ _a"> </span>http://doi.acm.org/10.1145/</span></div><div class="t m0 x1 h5 y2b ff4 fs2 fc0 sc0 ls0 ws0">1177352.1177355.</div><div class="t m0 x3 h6 y2c ff4 fs3 fc0 sc0 ls0 ws0">ACM<span class="_"> </span>Computing<span class="_"> </span>Surveys,<span class="_"> </span>V<span class="_ _3"></span>ol.<span class="_"> </span>38,<span class="_"> </span>No.<span class="_"> </span>4,<span class="_"> </span>Artic<span class="_ _1"></span>le<span class="_"> </span>13,<span class="_"> </span>Publication<span class="_"> </span>date:<span class="_"> </span>December<span class="_"> </span>2006.</div></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div>
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<div id="pf2" class="pf w0 h0" data-page-no="2"><div class="pc pc2 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6258e36bbe9ad24cfaacba87/bg2.jpg"><div class="t m1 x4 h7 y2d ff4 fs1 fc0 sc0 ls0 ws0">2<span class="_ _d"> </span><span class="ff3">A.<span class="_"> </span>Yilmaz<span class="_"> </span>et<span class="_"> </span>al.</span></div><div class="t m1 x4 h8 y2e ff1 fs4 fc0 sc0 ls0 ws0">1.<span class="_ _9"> </span>INTRODUCTION</div><div class="t m1 x4 h7 y2f ff4 fs1 fc0 sc0 ls0 ws0">Object<span class="_ _a"> </span>tracking<span class="_ _a"> </span>is<span class="_ _b"> </span>an<span class="_ _a"> </span>important<span class="_ _b"> </span>task<span class="_ _a"> </span>within<span class="_ _a"> </span>the<span class="_ _b"> </span>field<span class="_ _a"> </span>of<span class="_ _b"> </span>computer<span class="_ _a"> </span>vision.<span class="_ _a"> </span>The<span class="_ _b"> </span>prolif-</div><div class="t m1 x4 h7 y30 ff4 fs1 fc0 sc0 ls0 ws0">eration<span class="_ _b"> </span>of<span class="_ _b"> </span>high-powered<span class="_ _b"> </span>computers,<span class="_ _a"> </span>the<span class="_ _b"> </span>availability<span class="_ _b"> </span>of<span class="_ _b"> </span>high<span class="_ _b"> </span>quality<span class="_ _b"> </span>and<span class="_ _b"> </span>inexpensive</div><div class="t m1 x4 h7 y31 ff4 fs1 fc0 sc0 ls0 ws0">video<span class="_"> </span>cameras,<span class="_"> </span>and<span class="_ _6"> </span>the<span class="_"> </span>increasing<span class="_ _6"> </span>need<span class="_ _6"> </span>for<span class="_ _6"> </span>automated<span class="_"> </span>video<span class="_ _6"> </span>analysis<span class="_ _6"> </span>has<span class="_"> </span>generated<span class="_ _6"> </span>a</div><div class="t m1 x4 h7 y32 ff4 fs1 fc0 sc0 ls0 ws0">great<span class="_"> </span>deal<span class="_"> </span>of<span class="_"> </span>interest<span class="_ _6"> </span>in<span class="_"> </span>object<span class="_"> </span>tracking<span class="_"> </span>algorithms.<span class="_"> </span>There<span class="_"> </span>are<span class="_"> </span>three<span class="_"> </span>key<span class="_"> </span>steps<span class="_ _6"> </span>in<span class="_"> </span>video</div><div class="t m1 x4 h7 y33 ff4 fs1 fc0 sc0 ls0 ws0">analysis:<span class="_ _a"> </span>detection<span class="_ _6"> </span>of<span class="_ _a"> </span>interesting<span class="_ _a"> </span>moving<span class="_ _6"> </span>objects,<span class="_ _6"> </span>tracking<span class="_ _a"> </span>of<span class="_ _e"> </span>such<span class="_ _e"> </span>objects<span class="_ _e"> </span>from<span class="_ _e"> </span>frame</div><div class="t m1 x4 h7 y34 ff4 fs1 fc0 sc0 ls0 ws0">to<span class="_ _4"> </span>frame,<span class="_ _8"> </span>and<span class="_"> </span>analysis<span class="_ _8"> </span>of<span class="_ _4"> </span>object<span class="_ _4"> </span>tracks<span class="_ _8"> </span>to<span class="_"> </span>recognize<span class="_ _8"> </span>their<span class="_"> </span>beha<span class="_ _1"></span>vior<span class="_ _0"></span>.<span class="_ _4"> </span>Therefore,<span class="_ _8"> </span>the<span class="_ _4"> </span>use<span class="_ _4"> </span>of</div><div class="t m1 x4 h7 y35 ff4 fs1 fc0 sc0 ls0 ws0">object<span class="_"> </span>tracking<span class="_"> </span>is<span class="_"> </span>pertinent<span class="_"> </span>in<span class="_"> </span>the<span class="_"> </span>tasks<span class="_"> </span>of:</div><div class="t m1 x4 h7 y36 ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>motion-based<span class="_"> </span>recognition,<span class="_"> </span>that<span class="_"> </span>is,<span class="_"> </span>human<span class="_"> </span>identification<span class="_"> </span>based<span class="_"> </span>on<span class="_"> </span>gait,<span class="_"> </span>automatic<span class="_"> </span>ob-</div><div class="t m1 x5 h7 y37 ff4 fs1 fc0 sc0 ls0 ws0">ject<span class="_"> </span>detection,<span class="_"> </span>etc;</div><div class="t m1 x4 h7 y38 ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>automated<span class="_"> </span>surveillance,<span class="_"> </span>that<span class="_"> </span>is,<span class="_"> </span>monitoring<span class="_"> </span>a<span class="_"> </span>scene<span class="_"> </span>to<span class="_"> </span>detect<span class="_"> </span>suspicious<span class="_"> </span>activities<span class="_"> </span>or</div><div class="t m1 x5 h7 y39 ff4 fs1 fc0 sc0 ls0 ws0">unlikely<span class="_"> </span>events;</div><div class="t m1 x4 h7 y3a ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>video<span class="_ _5"> </span>indexing,<span class="_ _7"> </span>that<span class="_ _5"> </span>is,<span class="_ _5"> </span>automatic<span class="_ _5"> </span>annotation<span class="_ _5"> </span>and<span class="_ _5"> </span>retrieval<span class="_ _5"> </span>of<span class="_ _5"> </span>the<span class="_ _5"> </span>videos<span class="_ _5"> </span>in<span class="_ _7"> </span>multimedia</div><div class="t m1 x5 h7 y3b ff4 fs1 fc0 sc0 ls0 ws0">databases;</div><div class="t m1 x4 h7 y3c ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>human-computer<span class="_"> </span>interaction,<span class="_"> </span>that<span class="_"> </span>is<span class="_ _3"></span>,<span class="_"> </span>gesture<span class="_"> </span>recognition,<span class="_"> </span>eye<span class="_ _8"> </span>gaze<span class="_"> </span>tracking<span class="_"> </span>for<span class="_"> </span>data</div><div class="t m1 x5 h7 y3d ff4 fs1 fc0 sc0 ls0 ws0">input<span class="_"> </span>to<span class="_"> </span>computers<span class="_ _1"></span>,<span class="_"> </span>etc.;</div><div class="t m1 x4 h7 y3e ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>traffic<span class="_ _8"> </span>monitoring,<span class="_ _8"> </span>that<span class="_ _8"> </span>is<span class="_ _1"></span>,<span class="_ _8"> </span>real-time<span class="_ _8"> </span>gathering<span class="_ _8"> </span>of<span class="_ _8"> </span>traffic<span class="_ _8"> </span>statistics<span class="_ _8"> </span>to<span class="_ _4"> </span>direct<span class="_ _8"> </span>traffic<span class="_ _8"> </span>flow<span class="_ _f"></span>.</div><div class="t m1 x4 h7 y3f ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>vehicle<span class="_ _10"> </span>navigation,<span class="_ _10"> </span>that<span class="_ _11"> </span>is,<span class="_ _11"> </span>video-based<span class="_ _11"> </span>path<span class="_ _10"> </span>planning<span class="_ _11"> </span>and<span class="_ _10"> </span>obstacle<span class="_ _10"> </span>avoidance</div><div class="t m1 x5 h7 y40 ff4 fs1 fc0 sc0 ls0 ws0">capabilities<span class="_ _1"></span>.</div><div class="t m1 x6 h7 y41 ff4 fs1 fc0 sc0 ls0 ws0">In<span class="_ _e"> </span>its<span class="_ _a"> </span>simplest<span class="_ _e"> </span>form,<span class="_ _a"> </span>tracking<span class="_ _e"> </span>can<span class="_ _a"> </span>be<span class="_ _e"> </span>defined<span class="_ _a"> </span>as<span class="_ _e"> </span>the<span class="_ _a"> </span>problem<span class="_ _a"> </span>of<span class="_ _e"> </span>estimating<span class="_ _a"> </span>the<span class="_ _e"> </span>tra-</div><div class="t m1 x4 h7 y42 ff4 fs1 fc0 sc0 ls0 ws0">jectory<span class="_ _e"> </span>of<span class="_ _e"> </span>an<span class="_ _e"> </span>object<span class="_ _a"> </span>in<span class="_ _e"> </span>the<span class="_ _e"> </span>image<span class="_ _a"> </span>plane<span class="_ _e"> </span>as<span class="_ _e"> </span>it<span class="_ _a"> </span>moves<span class="_ _e"> </span>around<span class="_ _e"> </span>a<span class="_ _a"> </span>scene.<span class="_ _6"> </span>In<span class="_ _a"> </span>other<span class="_ _e"> </span>words,<span class="_ _6"> </span>a</div><div class="t m1 x4 h7 y43 ff4 fs1 fc0 sc0 ls0 ws0">tracker<span class="_ _5"> </span>assigns<span class="_ _5"> </span>consistent<span class="_ _5"> </span>labels<span class="_ _8"> </span>to<span class="_ _5"> </span>the<span class="_ _5"> </span>tracked<span class="_ _5"> </span>objects<span class="_ _5"> </span>in<span class="_ _8"> </span>different<span class="_ _5"> </span>frames<span class="_ _5"> </span>of<span class="_ _5"> </span>a<span class="_ _8"> </span>video<span class="_ _1"></span>.<span class="_ _5"> </span>Ad-</div><div class="t m1 x4 h7 y44 ff4 fs1 fc0 sc0 ls0 ws0">ditionally<span class="_ _f"></span>,<span class="_"> </span>depending<span class="_"> </span>on<span class="_"> </span>the<span class="_"> </span>tracking<span class="_"> </span>domain,<span class="_"> </span>a<span class="_"> </span>trac<span class="_ _1"></span>ker<span class="_"> </span>can<span class="_"> </span>also<span class="_"> </span>provide<span class="_"> </span>object-centric</div><div class="t m1 x4 h7 y45 ff4 fs1 fc0 sc0 ls0 ws0">information,<span class="_ _e"> </span>such<span class="_ _e"> </span>as<span class="_ _e"> </span>orientation,<span class="_ _e"> </span>area,<span class="_ _a"> </span>or<span class="_ _e"> </span>shape<span class="_ _e"> </span>of<span class="_ _a"> </span>an<span class="_ _e"> </span>object.<span class="_ _e"> </span>Tracking<span class="_ _e"> </span>objects<span class="_ _e"> </span>can<span class="_ _a"> </span>be</div><div class="t m1 x4 h7 y46 ff4 fs1 fc0 sc0 ls0 ws0">complex<span class="_"> </span>due<span class="_"> </span>to:</div><div class="t m1 x4 h7 y47 ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>loss<span class="_"> </span>of<span class="_"> </span>information<span class="_"> </span>caused<span class="_"> </span>by<span class="_"> </span>projection<span class="_"> </span>of<span class="_"> </span>the<span class="_"> </span>3D<span class="_"> </span>world<span class="_"> </span>on<span class="_"> </span>a<span class="_"> </span>2D<span class="_"> </span>image,</div><div class="t m1 x4 h7 y48 ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>noise<span class="_"> </span>in<span class="_"> </span>images,</div><div class="t m1 x4 h7 y49 ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>complex<span class="_"> </span>object<span class="_"> </span>motion,</div><div class="t m1 x4 h7 y4a ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>nonrigid<span class="_"> </span>or<span class="_"> </span>articulated<span class="_"> </span>nature<span class="_"> </span>of<span class="_"> </span>objects,</div><div class="t m1 x4 h7 y4b ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>partial<span class="_"> </span>and<span class="_"> </span>full<span class="_"> </span>object<span class="_"> </span>occlusions,</div><div class="t m1 x4 h7 y4c ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>complex<span class="_"> </span>object<span class="_"> </span>shapes,</div><div class="t m1 x4 h7 y4d ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>scene<span class="_"> </span>illumination<span class="_"> </span>changes,<span class="_"> </span>and</div><div class="t m1 x4 h7 y4e ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span>real-time<span class="_"> </span>processing<span class="_"> </span>requirements.</div><div class="t m1 x4 h7 y4f ff4 fs1 fc0 sc0 ls0 ws0">One<span class="_ _e"> </span>can<span class="_ _a"> </span>simplify<span class="_ _a"> </span>tracking<span class="_ _a"> </span>by<span class="_ _a"> </span>imposing<span class="_ _a"> </span>constraints<span class="_ _a"> </span>on<span class="_ _a"> </span>the<span class="_ _a"> </span>motion<span class="_ _a"> </span>and/or<span class="_ _a"> </span>appearance</div><div class="t m1 x4 h7 y50 ff4 fs1 fc0 sc0 ls0 ws0">of<span class="_ _6"> </span>objects.<span class="_"> </span>F<span class="_ _3"></span>or<span class="_ _6"> </span>example,<span class="_"> </span>almost<span class="_ _6"> </span>all<span class="_ _6"> </span>tracking<span class="_ _6"> </span>algorithms<span class="_ _6"> </span>assume<span class="_ _6"> </span>that<span class="_ _6"> </span>the<span class="_ _6"> </span>object<span class="_ _6"> </span>motion</div><div class="t m1 x4 h7 y51 ff4 fs1 fc0 sc0 ls0 ws0">is<span class="_ _9"> </span>smooth<span class="_ _9"> </span>with<span class="_ _9"> </span>no<span class="_ _9"> </span>abrupt<span class="_ _9"> </span>c<span class="_ _1"></span>hanges.<span class="_ _b"> </span>One<span class="_ _9"> </span>can<span class="_ _9"> </span>further<span class="_ _9"> </span>constrain<span class="_ _9"> </span>the<span class="_ _9"> </span>object<span class="_ _9"> </span>motion<span class="_ _9"> </span>to</div><div class="t m1 x4 h7 y52 ff4 fs1 fc0 sc0 ls0 ws0">be<span class="_ _b"> </span>of<span class="_ _b"> </span>constant<span class="_ _b"> </span>velocity<span class="_ _b"> </span>or<span class="_ _a"> </span>constant<span class="_ _b"> </span>acceleration<span class="_ _b"> </span>based<span class="_ _b"> </span>on<span class="_ _b"> </span>a<span class="_ _b"> </span>priori<span class="_ _b"> </span>information.<span class="_ _b"> </span>Prior</div><div class="t m1 x4 h7 y53 ff4 fs1 fc0 sc0 ls0 ws0">knowledge<span class="_ _9"> </span>about<span class="_ _b"> </span>the<span class="_ _9"> </span>number<span class="_ _9"> </span>and<span class="_ _b"> </span>the<span class="_ _9"> </span>size<span class="_ _b"> </span>of<span class="_ _9"> </span>objects,<span class="_ _b"> </span>or<span class="_ _9"> </span>the<span class="_ _b"> </span>object<span class="_ _9"> </span>appearance<span class="_ _9"> </span>and</div><div class="t m1 x4 h7 y54 ff4 fs1 fc0 sc0 ls0 ws0">shape,<span class="_"> </span>can<span class="_"> </span>also<span class="_"> </span>be<span class="_"> </span>used<span class="_"> </span>to<span class="_"> </span>simplify<span class="_"> </span>the<span class="_"> </span>problem.</div><div class="t m1 x6 h7 y55 ff4 fs1 fc0 sc0 ls0 ws0">Numerous<span class="_ _8"> </span>approaches<span class="_ _8"> </span>for<span class="_ _4"> </span>object<span class="_ _8"> </span>tracking<span class="_ _8"> </span>have<span class="_ _8"> </span>been<span class="_"> </span>proposed.<span class="_ _8"> </span>These<span class="_ _8"> </span>primarily<span class="_ _8"> </span>differ</div><div class="t m1 x4 h7 y56 ff4 fs1 fc0 sc0 ls0 ws0">from<span class="_"> </span>each<span class="_ _4"> </span>other<span class="_"> </span>based<span class="_"> </span>on<span class="_ _4"> </span>the<span class="_"> </span>w<span class="_ _1"></span>ay<span class="_ _4"> </span>they<span class="_"> </span>approach<span class="_ _4"> </span>the<span class="_"> </span>following<span class="_"> </span>questions:<span class="_ _4"> </span>Which<span class="_"> </span>object</div><div class="t m1 x4 h7 y57 ff4 fs1 fc0 sc0 ls0 ws0">representation<span class="_ _b"> </span>is<span class="_ _b"> </span>suitable<span class="_ _b"> </span>for<span class="_ _b"> </span>tracking?<span class="_ _a"> </span>Which<span class="_ _b"> </span>image<span class="_ _b"> </span>features<span class="_ _b"> </span>should<span class="_ _b"> </span>be<span class="_ _b"> </span>used?<span class="_ _b"> </span>How</div><div class="t m1 x4 h7 y58 ff4 fs1 fc0 sc0 ls0 ws0">should<span class="_ _a"> </span>the<span class="_ _a"> </span>motion,<span class="_ _a"> </span>appearance,<span class="_ _e"> </span>and<span class="_ _b"> </span>shape<span class="_ _e"> </span>of<span class="_ _a"> </span>the<span class="_ _a"> </span>object<span class="_ _a"> </span>be<span class="_ _b"> </span>modeled?<span class="_ _e"> </span>The<span class="_ _a"> </span>answers<span class="_ _a"> </span>to</div><div class="t m1 x4 h7 y59 ff4 fs1 fc0 sc0 ls0 ws0">these<span class="_ _8"> </span>questions<span class="_"> </span>depend<span class="_ _8"> </span>on<span class="_ _4"> </span>the<span class="_ _8"> </span>context/environment<span class="_"> </span>in<span class="_ _8"> </span>which<span class="_ _8"> </span>the<span class="_"> </span>trac<span class="_ _1"></span>king<span class="_ _8"> </span>is<span class="_"> </span>performed</div><div class="t m1 x4 h7 y5a ff4 fs1 fc0 sc0 ls0 ws0">and<span class="_ _e"> </span>the<span class="_ _a"> </span>end<span class="_ _e"> </span>use<span class="_ _a"> </span>for<span class="_ _a"> </span>which<span class="_ _e"> </span>the<span class="_ _a"> </span>tracking<span class="_ _e"> </span>information<span class="_ _a"> </span>is<span class="_ _e"> </span>being<span class="_ _a"> </span>sought.<span class="_ _a"> </span>A<span class="_ _e"> </span>large<span class="_ _a"> </span>number</div><div class="t m1 x4 h7 y5b ff4 fs1 fc0 sc0 ls0 ws0">of<span class="_ _6"> </span>tracking<span class="_"> </span>methods<span class="_ _6"> </span>have<span class="_ _6"> </span>been<span class="_ _6"> </span>proposed<span class="_ _6"> </span>which<span class="_"> </span>attempt<span class="_ _6"> </span>to<span class="_ _6"> </span>answer<span class="_ _6"> </span>these<span class="_ _6"> </span>questions<span class="_ _6"> </span>for</div><div class="t m1 x4 h7 y5c ff4 fs1 fc0 sc0 ls0 ws0">a<span class="_"> </span>variety<span class="_ _6"> </span>of<span class="_"> </span>scenarios.<span class="_"> </span>The<span class="_ _6"> </span>goal<span class="_"> </span>of<span class="_ _6"> </span>this<span class="_"> </span>survey<span class="_ _6"> </span>is<span class="_ _6"> </span>to<span class="_"> </span>group<span class="_ _6"> </span>tracking<span class="_"> </span>methods<span class="_ _6"> </span>into<span class="_"> </span>broad</div><div class="t m1 x7 h6 y2c ff4 fs3 fc0 sc0 ls0 ws0">ACM<span class="_"> </span>Computing<span class="_"> </span>Surveys,<span class="_"> </span>V<span class="_ _3"></span>ol.<span class="_"> </span>38,<span class="_"> </span>No.<span class="_"> </span>4,<span class="_"> </span>Artic<span class="_ _1"></span>le<span class="_"> </span>13,<span class="_"> </span>Publication<span class="_"> </span>date:<span class="_"> </span>December<span class="_"> </span>2006.</div></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div>
<div id="pf3" class="pf w0 h0" data-page-no="3"><div class="pc pc3 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6258e36bbe9ad24cfaacba87/bg3.jpg"><div class="t m1 x1 h7 y2d ff3 fs1 fc0 sc0 ls0 ws0">Object<span class="_"> </span>T<span class="_ _3"></span>racking:<span class="_"> </span>A<span class="_"> </span>Survey<span class="_ _12"> </span><span class="ff4">3</span></div><div class="t m1 x1 h7 y5d ff4 fs1 fc0 sc0 ls0 ws0">categories<span class="_ _6"> </span>and<span class="_ _6"> </span>provide<span class="_ _6"> </span>comprehensive<span class="_ _6"> </span>descriptions<span class="_ _6"> </span>of<span class="_ _6"> </span>representative<span class="_ _6"> </span>methods<span class="_ _e"> </span>in<span class="_ _6"> </span>each</div><div class="t m1 x1 h7 y5e ff4 fs1 fc0 sc0 ls0 ws0">category<span class="_ _f"></span>.<span class="_ _b"> </span>W<span class="_ _3"></span>e<span class="_ _a"> </span>aspire<span class="_ _b"> </span>to<span class="_ _b"> </span>give<span class="_ _b"> </span>readers,<span class="_ _a"> </span>who<span class="_ _b"> </span>require<span class="_ _b"> </span>a<span class="_ _b"> </span>tracker<span class="_ _a"> </span>for<span class="_ _b"> </span>a<span class="_ _b"> </span>certain<span class="_ _b"> </span>application,</div><div class="t m1 x1 h7 y5f ff4 fs1 fc0 sc0 ls0 ws0">the<span class="_ _b"> </span>ability<span class="_ _a"> </span>to<span class="_ _b"> </span>select<span class="_ _b"> </span>the<span class="_ _b"> </span>most<span class="_ _b"> </span>suitable<span class="_ _a"> </span>tracking<span class="_ _b"> </span>algorithm<span class="_ _b"> </span>for<span class="_ _b"> </span>their<span class="_ _a"> </span>particular<span class="_ _b"> </span>needs.</div><div class="t m1 x1 h7 y60 ff4 fs1 fc0 sc0 ls0 ws0">Moreover<span class="_ _f"></span>,<span class="_ _4"> </span>we<span class="_ _8"> </span>aim<span class="_ _8"> </span>to<span class="_ _8"> </span>identify<span class="_ _8"> </span>new<span class="_ _8"> </span>trends<span class="_ _8"> </span>and<span class="_ _4"> </span>ideas<span class="_ _8"> </span>in<span class="_ _8"> </span>the<span class="_ _8"> </span>tracking<span class="_ _8"> </span>community<span class="_ _8"> </span>and<span class="_ _8"> </span>hope</div><div class="t m1 x1 h7 y61 ff4 fs1 fc0 sc0 ls0 ws0">to<span class="_"> </span>provide<span class="_"> </span>insight<span class="_"> </span>for<span class="_"> </span>the<span class="_"> </span>development<span class="_"> </span>of<span class="_"> </span>new<span class="_"> </span>tracking<span class="_"> </span>methods<span class="_ _1"></span>.</div><div class="t m1 x8 h7 y62 ff4 fs1 fc0 sc0 ls0 ws0">Our<span class="_ _a"> </span>survey<span class="_ _a"> </span>is<span class="_ _a"> </span>focused<span class="_ _b"> </span>on<span class="_ _e"> </span>methodologies<span class="_ _b"> </span>for<span class="_ _e"> </span>tracking<span class="_ _a"> </span>objects<span class="_ _b"> </span>in<span class="_ _e"> </span>general<span class="_ _b"> </span>and<span class="_ _e"> </span>not<span class="_ _b"> </span>on</div><div class="t m1 x1 h7 y63 ff4 fs1 fc0 sc0 ls0 ws0">trackers<span class="_ _8"> </span>tailored<span class="_ _8"> </span>for<span class="_ _8"> </span>specific<span class="_ _8"> </span>objects,<span class="_ _8"> </span>for<span class="_ _8"> </span>example,<span class="_ _8"> </span>person<span class="_ _8"> </span>trackers<span class="_ _8"> </span>that<span class="_ _8"> </span>use<span class="_ _8"> </span>human<span class="_ _8"> </span>kine-</div><div class="t m1 x1 h7 y64 ff4 fs1 fc0 sc0 ls0 ws0">matics<span class="_ _8"> </span>as<span class="_ _4"> </span>the<span class="_ _8"> </span>basis<span class="_ _4"> </span>of<span class="_ _8"> </span>their<span class="_ _4"> </span>implementation.<span class="_ _8"> </span>There<span class="_ _4"> </span>has<span class="_ _8"> </span>been<span class="_ _4"> </span>substantial<span class="_ _8"> </span>work<span class="_ _4"> </span>on<span class="_ _8"> </span>track-</div><div class="t m1 x1 h7 y65 ff4 fs1 fc0 sc0 ls0 ws0">ing<span class="_ _8"> </span>humans<span class="_ _4"> </span>using<span class="_ _8"> </span>articulated<span class="_ _4"> </span>object<span class="_ _8"> </span>models<span class="_ _8"> </span>that<span class="_"> </span>has<span class="_ _8"> </span>been<span class="_ _8"> </span>discussed<span class="_ _8"> </span>and<span class="_ _4"> </span>categorized<span class="_ _8"> </span>in</div><div class="t m1 x1 h7 y66 ff4 fs1 fc0 sc0 ls0 ws0">the<span class="_ _6"> </span>surveys<span class="_ _6"> </span>by<span class="_ _6"> </span>Aggarwal<span class="_"> </span>and<span class="_ _6"> </span>Cai<span class="_ _6"> </span>[1999],<span class="_ _6"> </span>Gavrilla<span class="_ _6"> </span>[1999],<span class="_ _6"> </span>and<span class="_"> </span>Moeslund<span class="_ _6"> </span>and<span class="_ _6"> </span>Granum</div><div class="t m1 x1 h7 y67 ff4 fs1 fc0 sc0 ls0 ws0">[2001].<span class="_ _a"> </span>W<span class="_ _3"></span>e<span class="_ _a"> </span>will,<span class="_ _a"> </span>however<span class="_ _0"></span>,<span class="_ _a"> </span>include<span class="_ _a"> </span>some<span class="_ _a"> </span>works<span class="_ _a"> </span>on<span class="_ _a"> </span>the<span class="_ _a"> </span>articulated<span class="_ _a"> </span>object<span class="_ _a"> </span>trackers<span class="_ _a"> </span>that</div><div class="t m1 x1 h7 y68 ff4 fs1 fc0 sc0 ls0 ws0">are<span class="_"> </span>also<span class="_"> </span>applicable<span class="_"> </span>to<span class="_"> </span>domains<span class="_"> </span>other<span class="_"> </span>than<span class="_"> </span>articulated<span class="_"> </span>objects<span class="_ _1"></span>.</div><div class="t m1 x8 h7 y69 ff4 fs1 fc0 sc0 ls0 ws0">W<span class="_ _3"></span>e<span class="_ _6"> </span>follow<span class="_ _e"> </span>a<span class="_ _6"> </span>bottom-up<span class="_ _e"> </span>approach<span class="_ _6"> </span>in<span class="_ _e"> </span>describing<span class="_ _6"> </span>the<span class="_ _e"> </span>issues<span class="_ _e"> </span>that<span class="_ _6"> </span>need<span class="_ _e"> </span>to<span class="_ _e"> </span>be<span class="_ _6"> </span>addressed</div><div class="t m1 x1 h7 y6a ff4 fs1 fc0 sc0 ls0 ws0">when<span class="_"> </span>one<span class="_ _6"> </span>sets<span class="_ _6"> </span>out<span class="_ _6"> </span>to<span class="_ _6"> </span>build<span class="_ _6"> </span>an<span class="_ _6"> </span>object<span class="_ _6"> </span>tracker<span class="_ _f"></span>.<span class="_ _6"> </span>The<span class="_ _6"> </span>first<span class="_ _6"> </span>issue<span class="_ _6"> </span>is<span class="_ _6"> </span>defining<span class="_ _6"> </span>a<span class="_ _6"> </span>suitable<span class="_"> </span>rep-</div><div class="t m1 x1 h7 y6b ff4 fs1 fc0 sc0 ls0 ws0">resentation<span class="_ _b"> </span>of<span class="_ _9"> </span>the<span class="_ _b"> </span>object.<span class="_ _9"> </span>In<span class="_ _b"> </span>Section<span class="_ _9"> </span>2,<span class="_ _b"> </span>we<span class="_ _b"> </span>will<span class="_ _9"> </span>describe<span class="_ _b"> </span>some<span class="_ _9"> </span>common<span class="_ _b"> </span>object<span class="_ _b"> </span>shape</div><div class="t m1 x1 h7 y6c ff4 fs1 fc0 sc0 ls0 ws0">representations<span class="_ _1"></span>,<span class="_ _e"> </span>for<span class="_ _e"> </span>example,<span class="_ _6"> </span>points,<span class="_ _6"> </span>primitive<span class="_ _e"> </span>geometric<span class="_ _e"> </span>shapes<span class="_ _e"> </span>and<span class="_ _e"> </span>object<span class="_ _e"> </span>contours,</div><div class="t m1 x1 h7 y6d ff4 fs1 fc0 sc0 ls0 ws0">and<span class="_ _4"> </span>appearance<span class="_ _4"> </span>representations.<span class="_ _8"> </span>The<span class="_"> </span>next<span class="_ _8"> </span>issue<span class="_"> </span>is<span class="_ _8"> </span>the<span class="_"> </span>selection<span class="_ _8"> </span>of<span class="_"> </span>image<span class="_ _8"> </span>features<span class="_"> </span>used</div><div class="t m1 x1 h7 y6e ff4 fs1 fc0 sc0 ls0 ws0">as<span class="_ _5"> </span>an<span class="_ _5"> </span>input<span class="_ _8"> </span>for<span class="_ _5"> </span>the<span class="_ _5"> </span>tracker<span class="_ _f"></span>.<span class="_ _8"> </span>In<span class="_ _5"> </span>Section<span class="_ _5"> </span>3,<span class="_ _5"> </span>we<span class="_ _5"> </span>discuss<span class="_ _8"> </span>various<span class="_ _5"> </span>image<span class="_ _5"> </span>features,<span class="_ _7"> </span>such<span class="_ _5"> </span>as<span class="_ _8"> </span>color<span class="_ _f"></span>,</div><div class="t m1 x1 h7 y6f ff4 fs1 fc0 sc0 ls0 ws0">motion,<span class="_ _e"> </span>edges,<span class="_ _e"> </span>etc.,<span class="_ _a"> </span>which<span class="_ _e"> </span>are<span class="_ _a"> </span>commonly<span class="_ _a"> </span>used<span class="_ _a"> </span>in<span class="_ _a"> </span>object<span class="_ _a"> </span>tracking<span class="_ _1"></span>.<span class="_ _a"> </span>Almost<span class="_ _a"> </span>all<span class="_ _e"> </span>tracking</div><div class="t m1 x1 h7 y70 ff4 fs1 fc0 sc0 ls0 ws0">algorithms<span class="_ _6"> </span>require<span class="_ _6"> </span>detection<span class="_ _6"> </span>of<span class="_ _6"> </span>the<span class="_ _6"> </span>objects<span class="_ _6"> </span>either<span class="_ _e"> </span>in<span class="_ _6"> </span>the<span class="_ _6"> </span>first<span class="_ _6"> </span>frame<span class="_ _6"> </span>or<span class="_ _6"> </span>in<span class="_ _6"> </span>every<span class="_ _e"> </span>frame.</div><div class="t m1 x1 h7 y71 ff4 fs1 fc0 sc0 ls0 ws0">Section<span class="_ _e"> </span>4<span class="_ _e"> </span>summarizes<span class="_ _e"> </span>the<span class="_ _e"> </span>general<span class="_ _e"> </span>strategies<span class="_ _e"> </span>for<span class="_ _e"> </span>detecting<span class="_ _e"> </span>the<span class="_ _e"> </span>objects<span class="_ _e"> </span>in<span class="_ _e"> </span>a<span class="_ _e"> </span>scene.<span class="_ _6"> </span>The</div><div class="t m1 x1 h7 y72 ff4 fs1 fc0 sc0 ls0 ws0">suitability<span class="_ _b"> </span>of<span class="_ _b"> </span>a<span class="_ _9"> </span>particular<span class="_ _b"> </span>tracking<span class="_ _b"> </span>algorithm<span class="_ _b"> </span>depends<span class="_ _b"> </span>on<span class="_ _b"> </span>object<span class="_ _9"> </span>appearances<span class="_ _3"></span>,<span class="_ _9"> </span>object</div><div class="t m1 x1 h7 y73 ff4 fs1 fc0 sc0 ls0 ws0">shapes,<span class="_"> </span>number<span class="_"> </span>of<span class="_"> </span>objects<span class="_ _1"></span>,<span class="_"> </span>object<span class="_"> </span>and<span class="_"> </span>camera<span class="_"> </span>motions,<span class="_"> </span>and<span class="_"> </span>illumination<span class="_"> </span>conditions.<span class="_"> </span>In</div><div class="t m1 x1 h7 y74 ff4 fs1 fc0 sc0 ls0 ws0">Section<span class="_"> </span>5,<span class="_ _6"> </span>we<span class="_"> </span>categorize<span class="_ _6"> </span>and<span class="_"> </span>describe<span class="_ _6"> </span>the<span class="_"> </span>existing<span class="_ _6"> </span>tracking<span class="_"> </span>methods<span class="_ _6"> </span>and<span class="_"> </span>explain<span class="_ _6"> </span>their</div><div class="t m1 x1 h7 y75 ff4 fs1 fc0 sc0 ls0 ws0">strengths<span class="_ _8"> </span>and<span class="_"> </span>weaknesses<span class="_ _8"> </span>in<span class="_"> </span>a<span class="_ _8"> </span>summary<span class="_ _4"> </span>section<span class="_ _8"> </span>at<span class="_"> </span>the<span class="_ _8"> </span>end<span class="_"> </span>of<span class="_ _8"> </span>each<span class="_ _8"> </span>category<span class="_ _f"></span>.<span class="_"> </span>In<span class="_ _8"> </span>Section</div><div class="t m1 x1 h7 y76 ff4 fs1 fc0 sc0 ls0 ws0">6,<span class="_ _4"> </span>important<span class="_"> </span>issues<span class="_ _8"> </span>relevant<span class="_"> </span>to<span class="_ _8"> </span>object<span class="_"> </span>tracking<span class="_ _8"> </span>are<span class="_"> </span>discussed.<span class="_ _8"> </span>Section<span class="_"> </span>7<span class="_ _4"> </span>presents<span class="_ _4"> </span>future</div><div class="t m1 x1 h7 y77 ff4 fs1 fc0 sc0 ls0 ws0">directions<span class="_"> </span>in<span class="_"> </span>tracking<span class="_ _4"> </span>research.<span class="_"> </span>Finally<span class="_ _f"></span>,<span class="_ _4"> </span>concluding<span class="_"> </span>remarks<span class="_"> </span>are<span class="_ _4"> </span>sketched<span class="_"> </span>in<span class="_"> </span>Section<span class="_"> </span>8.</div><div class="t m1 x1 h8 y78 ff1 fs4 fc0 sc0 ls0 ws0">2.<span class="_ _9"> </span>OBJECT<span class="_"> </span>REPRESENT<span class="_ _0"></span>A<span class="_ _3"></span>TION</div><div class="t m1 x1 h7 y79 ff4 fs1 fc0 sc0 ls0 ws0">In<span class="_ _5"> </span>a<span class="_ _8"> </span>tracking<span class="_ _5"> </span>scenario,<span class="_ _8"> </span>an<span class="_ _5"> </span>object<span class="_ _8"> </span>can<span class="_ _5"> </span>be<span class="_ _8"> </span>defined<span class="_ _8"> </span>as<span class="_ _5"> </span>anything<span class="_ _8"> </span>that<span class="_ _5"> </span>is<span class="_ _8"> </span>of<span class="_ _5"> </span>interest<span class="_ _8"> </span>for<span class="_ _8"> </span>further</div><div class="t m1 x1 h7 y7a ff4 fs1 fc0 sc0 ls0 ws0">analysis.<span class="_ _6"> </span>F<span class="_ _3"></span>or<span class="_ _a"> </span>instance,<span class="_ _e"> </span>boats<span class="_ _e"> </span>on<span class="_ _a"> </span>the<span class="_ _e"> </span>sea,<span class="_ _a"> </span>fish<span class="_ _e"> </span>inside<span class="_ _a"> </span>an<span class="_ _e"> </span>aquarium,<span class="_ _a"> </span>vehicles<span class="_ _e"> </span>on<span class="_ _a"> </span>a<span class="_ _e"> </span>road,</div><div class="t m1 x1 h7 y7b ff4 fs1 fc0 sc0 ls0 ws0">planes<span class="_"> </span>in<span class="_"> </span>the<span class="_"> </span>air<span class="_ _0"></span>,<span class="_"> </span>people<span class="_"> </span>walking<span class="_"> </span>on<span class="_"> </span>a<span class="_"> </span>road,<span class="_"> </span>or<span class="_"> </span>bubbles<span class="_"> </span>in<span class="_"> </span>the<span class="_"> </span>water<span class="_"> </span>are<span class="_"> </span>a<span class="_"> </span>set<span class="_"> </span>of<span class="_"> </span>objects</div><div class="t m1 x1 h7 y7c ff4 fs1 fc0 sc0 ls0 ws0">that<span class="_ _b"> </span>may<span class="_ _a"> </span>be<span class="_ _b"> </span>important<span class="_ _b"> </span>to<span class="_ _a"> </span>track<span class="_ _b"> </span>in<span class="_ _b"> </span>a<span class="_ _b"> </span>specific<span class="_ _a"> </span>domain.<span class="_ _b"> </span>Objects<span class="_ _b"> </span>can<span class="_ _b"> </span>be<span class="_ _a"> </span>represented<span class="_ _b"> </span>by</div><div class="t m1 x1 h7 y7d ff4 fs1 fc0 sc0 ls0 ws0">their<span class="_ _e"> </span>shapes<span class="_ _a"> </span>and<span class="_ _e"> </span>appearances.<span class="_ _e"> </span>In<span class="_ _a"> </span>this<span class="_ _e"> </span>section,<span class="_ _a"> </span>we<span class="_ _a"> </span>will<span class="_ _e"> </span>first<span class="_ _a"> </span>describe<span class="_ _a"> </span>the<span class="_ _e"> </span>object<span class="_ _a"> </span>shape</div><div class="t m1 x1 h7 y7e ff4 fs1 fc0 sc0 ls0 ws0">representations<span class="_ _8"> </span>commonly<span class="_"> </span>employed<span class="_ _8"> </span>for<span class="_ _8"> </span>tracking<span class="_"> </span>and<span class="_ _8"> </span>then<span class="_ _8"> </span>address<span class="_"> </span>the<span class="_ _8"> </span>joint<span class="_ _8"> </span>shape<span class="_"> </span>and</div><div class="t m1 x1 h7 y7f ff4 fs1 fc0 sc0 ls0 ws0">appearance<span class="_"> </span>representations<span class="_ _1"></span>.</div><div class="t m1 x1 h7 y80 ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span><span class="ff3">P<span class="_ _3"></span>oints<span class="_ _1"></span>.<span class="_ _13"> </span><span class="ff4">The<span class="_ _13"> </span>object<span class="_ _13"> </span>is<span class="_ _13"> </span>represented<span class="_ _13"> </span>by<span class="_ _13"> </span>a<span class="_ _13"> </span>point,<span class="_ _13"> </span>that<span class="_ _13"> </span>is<span class="_ _1"></span>,<span class="_ _13"> </span>the<span class="_ _13"> </span>centroid<span class="_ _13"> </span>(Figure<span class="_ _13"> </span>1(a))</span></span></div><div class="t m1 x9 h7 y81 ff4 fs1 fc0 sc0 ls0 ws0">[V<span class="_ _0"></span>eenman<span class="_ _8"> </span>et<span class="_ _8"> </span>al.<span class="_ _8"> </span>2001]<span class="_ _8"> </span>or<span class="_ _8"> </span>by<span class="_ _8"> </span>a<span class="_ _8"> </span>set<span class="_ _8"> </span>of<span class="_ _8"> </span>points<span class="_ _8"> </span>(Figure<span class="_ _8"> </span>1(b))<span class="_ _8"> </span>[Serby<span class="_ _5"> </span>et<span class="_ _8"> </span>al.<span class="_ _8"> </span>2004].<span class="_ _8"> </span>In<span class="_ _8"> </span>general,</div><div class="t m1 x9 h7 y82 ff4 fs1 fc0 sc0 ls0 ws0">the<span class="_"> </span>point<span class="_"> </span>representation<span class="_"> </span>is<span class="_"> </span>suitable<span class="_"> </span>for<span class="_"> </span>tracking<span class="_"> </span>objects<span class="_"> </span>that<span class="_"> </span>occupy<span class="_"> </span>small<span class="_ _4"> </span>regions<span class="_"> </span>in</div><div class="t m1 x9 h7 y83 ff4 fs1 fc0 sc0 ls0 ws0">an<span class="_"> </span>image.(see<span class="_"> </span>Section<span class="_"> </span>5.1).</div><div class="t m1 x1 h7 y84 ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span><span class="ff3">Primitive<span class="_ _14"> </span>geometric<span class="_ _14"> </span>shapes<span class="_ _3"></span>.<span class="_ _13"> </span><span class="ff4">Object<span class="_ _14"> </span>shape<span class="_ _14"> </span>is<span class="_ _13"> </span>represented<span class="_ _14"> </span>by<span class="_ _14"> </span>a<span class="_ _13"> </span>rectangle,<span class="_ _14"> </span>ellipse</span></span></div><div class="t m1 x9 h7 y85 ff4 fs1 fc0 sc0 ls0 ws0">(Figure<span class="_"> </span>1(c),<span class="_"> </span>(d)<span class="_ _6"> </span>[Comaniciu<span class="_"> </span>et<span class="_ _6"> </span>al.<span class="_"> </span>2003],<span class="_ _6"> </span>etc.<span class="_"> </span>Object<span class="_"> </span>motion<span class="_ _6"> </span>for<span class="_"> </span>such<span class="_ _6"> </span>representations</div><div class="t m1 x9 h7 y86 ff4 fs1 fc0 sc0 ls0 ws0">is<span class="_"> </span>usually<span class="_ _4"> </span>modeled<span class="_"> </span>by<span class="_"> </span>translation,<span class="_ _8"> </span>affine,<span class="_"> </span>or<span class="_"> </span>projective<span class="_ _4"> </span>(homography)<span class="_"> </span>transformation</div><div class="t m1 x9 h7 y87 ff4 fs1 fc0 sc0 ls0 ws0">(see<span class="_ _8"> </span>Section<span class="_ _4"> </span>5.2<span class="_ _8"> </span>for<span class="_ _4"> </span>details).<span class="_ _8"> </span>Though<span class="_ _4"> </span>primitive<span class="_ _8"> </span>geometric<span class="_ _4"> </span>shapes<span class="_ _8"> </span>are<span class="_ _4"> </span>more<span class="_ _8"> </span>suitable<span class="_ _8"> </span>for</div><div class="t m1 x9 h7 y88 ff4 fs1 fc0 sc0 ls0 ws0">representing<span class="_"> </span>simple<span class="_"> </span>rigid<span class="_"> </span>objects<span class="_ _1"></span>,<span class="_"> </span>they<span class="_"> </span>are<span class="_"> </span>also<span class="_"> </span>used<span class="_"> </span>for<span class="_"> </span>tracking<span class="_"> </span>nonrigid<span class="_"> </span>objects<span class="_ _1"></span>.</div><div class="t m1 x1 h7 y89 ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span><span class="ff3">Object<span class="_ _9"> </span>silhouette<span class="_ _b"> </span>and<span class="_ _9"> </span>contour<span class="_ _f"></span>.<span class="_ _9"> </span><span class="ff4">Contour<span class="_ _b"> </span>representation<span class="_ _9"> </span>defines<span class="_ _b"> </span>the<span class="_ _9"> </span>boundary<span class="_ _b"> </span>of<span class="_ _9"> </span>an</span></span></div><div class="t m1 x9 h7 y8a ff4 fs1 fc0 sc0 ls0 ws0">object<span class="_ _e"> </span>(Figure<span class="_ _6"> </span>1(g),<span class="_ _e"> </span>(h).<span class="_ _e"> </span>The<span class="_ _e"> </span>region<span class="_ _e"> </span>inside<span class="_ _e"> </span>the<span class="_ _e"> </span>contour<span class="_ _e"> </span>is<span class="_ _e"> </span>called<span class="_ _e"> </span>the<span class="_ _a"> </span>silhouette<span class="_ _e"> </span>of<span class="_ _e"> </span>the</div><div class="t m1 x9 h7 y8b ff4 fs1 fc0 sc0 ls0 ws0">object<span class="_ _8"> </span>(see<span class="_ _5"> </span>Figure<span class="_ _8"> </span>1(i)<span class="_ _8"> </span>).<span class="_ _5"> </span>Silhouette<span class="_ _8"> </span>and<span class="_ _8"> </span>contour<span class="_ _8"> </span>representations<span class="_ _8"> </span>are<span class="_ _5"> </span>suitable<span class="_ _8"> </span>for<span class="_ _8"> </span>track-</div><div class="t m1 x9 h7 y8c ff4 fs1 fc0 sc0 ls0 ws0">ing<span class="_"> </span>complex<span class="_"> </span>nonrigid<span class="_"> </span>shapes<span class="_"> </span>[Yilmaz<span class="_"> </span>et<span class="_"> </span>al.<span class="_"> </span>2004].</div><div class="t m1 x1 h6 y2c ff4 fs3 fc0 sc0 ls0 ws0">ACM<span class="_"> </span>Computing<span class="_"> </span>Surveys,<span class="_"> </span>V<span class="_ _3"></span>ol.<span class="_"> </span>38,<span class="_"> </span>No.<span class="_"> </span>4,<span class="_"> </span>Artic<span class="_ _1"></span>le<span class="_"> </span>13,<span class="_"> </span>Publication<span class="_"> </span>date:<span class="_"> </span>December<span class="_"> </span>2006.</div></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div>
<div id="pf4" class="pf w0 h0" data-page-no="4"><div class="pc pc4 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6258e36bbe9ad24cfaacba87/bg4.jpg"><div class="t m1 x4 h7 y2d ff4 fs1 fc0 sc0 ls0 ws0">4<span class="_ _d"> </span><span class="ff3">A.<span class="_"> </span>Yilmaz<span class="_"> </span>et<span class="_"> </span>al.</span></div><div class="t m1 xa h5 y8d ff1 fs2 fc0 sc0 ls0 ws0">Fig.<span class="_ _6"> </span>1<span class="ff4">.<span class="_ _15"> </span>Object<span class="_ _6"> </span>representations.<span class="_ _6"> </span>(a)<span class="_ _e"> </span>Centroid,<span class="_ _e"> </span>(b)<span class="_ _6"> </span>multiple<span class="_ _e"> </span>points,<span class="_ _6"> </span>(c)<span class="_ _e"> </span>rectangular</span></div><div class="t m1 xa h5 y8e ff4 fs2 fc0 sc0 ls0 ws0">patch,<span class="_ _2"> </span>(d)<span class="_ _6"> </span>elliptical<span class="_ _6"> </span>patch,<span class="_ _6"> </span>(e)<span class="_ _6"> </span>part-based<span class="_ _2"> </span>multiple<span class="_ _6"> </span>patches,<span class="_ _2"> </span>(f)<span class="_ _6"> </span>object<span class="_ _6"> </span>skeleton,<span class="_ _6"> </span>(g)</div><div class="t m1 xa h5 y8f ff4 fs2 fc0 sc0 ls0 ws0">complete<span class="_"> </span>object<span class="_"> </span>contour<span class="_ _0"></span>,<span class="_"> </span>(h)<span class="_"> </span>control<span class="_"> </span>points<span class="_"> </span>on<span class="_"> </span>object<span class="_"> </span>contour<span class="_ _3"></span>,<span class="_"> </span>(i)<span class="_"> </span>object<span class="_"> </span>silhouette.</div><div class="t m1 x4 h7 y90 ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span><span class="ff3">Articulated<span class="_ _b"> </span>shape<span class="_ _a"> </span>models<span class="_ _1"></span>.<span class="_ _a"> </span><span class="ff4">Articulated<span class="_ _b"> </span>objects<span class="_ _b"> </span>are<span class="_ _a"> </span>composed<span class="_ _b"> </span>of<span class="_ _a"> </span>body<span class="_ _b"> </span>parts<span class="_ _a"> </span>that<span class="_ _b"> </span>are</span></span></div><div class="t m1 x5 h7 y91 ff4 fs1 fc0 sc0 ls0 ws0">held<span class="_"> </span>together<span class="_ _4"> </span>with<span class="_"> </span>joints<span class="_ _1"></span>.<span class="_"> </span>F<span class="_ _0"></span>or<span class="_"> </span>example,<span class="_"> </span>the<span class="_ _4"> </span>human<span class="_"> </span>body<span class="_ _4"> </span>is<span class="_"> </span>an<span class="_ _4"> </span>articulated<span class="_"> </span>object<span class="_"> </span>with</div><div class="t m1 x5 h7 y92 ff4 fs1 fc0 sc0 ls0 ws0">torso,<span class="_"> </span>legs,<span class="_ _6"> </span>hands,<span class="_"> </span>head,<span class="_ _e"> </span>and<span class="_ _6"> </span>feet<span class="_ _e"> </span>connected<span class="_ _6"> </span>by<span class="_ _e"> </span>joints.<span class="_"> </span>The<span class="_ _e"> </span>relationship<span class="_ _6"> </span>between<span class="_ _e"> </span>the</div><div class="t m1 x5 h7 y93 ff4 fs1 fc0 sc0 ls0 ws0">parts<span class="_ _8"> </span>are<span class="_ _8"> </span>governed<span class="_ _8"> </span>by<span class="_ _5"> </span>kinematic<span class="_ _8"> </span>motion<span class="_ _8"> </span>models,<span class="_ _8"> </span>for<span class="_ _5"> </span>example,<span class="_ _8"> </span>joint<span class="_ _8"> </span>angle,<span class="_ _5"> </span>etc.<span class="_ _8"> </span>In<span class="_ _8"> </span>order</div><div class="t m1 x5 h7 y94 ff4 fs1 fc0 sc0 ls0 ws0">to<span class="_ _5"> </span>represent<span class="_ _5"> </span>an<span class="_ _8"> </span>articulated<span class="_ _5"> </span>object,<span class="_ _5"> </span>one<span class="_ _8"> </span>can<span class="_ _5"> </span>model<span class="_ _5"> </span>the<span class="_ _8"> </span>constituent<span class="_ _5"> </span>parts<span class="_ _5"> </span>using<span class="_ _5"> </span>cylinders</div><div class="t m1 x5 h7 y95 ff4 fs1 fc0 sc0 ls0 ws0">or<span class="_"> </span>ellipses<span class="_"> </span>as<span class="_"> </span>shown<span class="_"> </span>in<span class="_"> </span>Figure<span class="_"> </span>1(e).</div><div class="t m1 x4 h7 y96 ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span><span class="ff3">Skeletal<span class="_ _9"> </span>models<span class="_ _3"></span>.<span class="_ _9"> </span><span class="ff4">Object<span class="_ _9"> </span>skeleton<span class="_ _9"> </span>can<span class="_ _b"> </span>be<span class="_ _9"> </span>extracted<span class="_ _9"> </span>by<span class="_ _9"> </span>applying<span class="_ _b"> </span>medial<span class="_ _9"> </span>axis<span class="_ _9"> </span>trans-</span></span></div><div class="t m1 x5 h7 y97 ff4 fs1 fc0 sc0 ls0 ws0">form<span class="_"> </span>to<span class="_"> </span>the<span class="_ _6"> </span>object<span class="_"> </span>silhouette<span class="_ _6"> </span>[Ballard<span class="_"> </span>and<span class="_ _6"> </span>Brown<span class="_"> </span>1982,<span class="_ _6"> </span>Chap.<span class="_"> </span>8].<span class="_"> </span>This<span class="_"> </span>model<span class="_ _6"> </span>is<span class="_"> </span>com-</div><div class="t m1 x5 h7 y98 ff4 fs1 fc0 sc0 ls0 ws0">monly<span class="_ _5"> </span>used<span class="_ _5"> </span>as<span class="_ _5"> </span>a<span class="_ _8"> </span>shape<span class="_ _5"> </span>representation<span class="_ _5"> </span>for<span class="_ _5"> </span>recognizing<span class="_ _5"> </span>objects<span class="_ _8"> </span>[Ali<span class="_ _7"> </span>and<span class="_ _8"> </span>Aggarw<span class="_ _1"></span>al<span class="_ _5"> </span>2001].</div><div class="t m1 x5 h7 y99 ff4 fs1 fc0 sc0 ls0 ws0">Skeleton<span class="_"> </span>representation<span class="_"> </span>can<span class="_"> </span>be<span class="_"> </span>used<span class="_"> </span>to<span class="_"> </span>model<span class="_"> </span>both<span class="_"> </span>articulated<span class="_"> </span>and<span class="_"> </span>rigid<span class="_"> </span>objects<span class="_"> </span>(see</div><div class="t m1 x5 h7 y9a ff4 fs1 fc0 sc0 ls0 ws0">Figure<span class="_"> </span>1(f).</div><div class="t m1 x6 h7 y9b ff4 fs1 fc0 sc0 ls0 ws0">There<span class="_ _a"> </span>are<span class="_ _a"> </span>a<span class="_ _a"> </span>number<span class="_ _b"> </span>of<span class="_ _e"> </span>ways<span class="_ _e"> </span>to<span class="_ _b"> </span>represent<span class="_ _e"> </span>the<span class="_ _b"> </span>appearance<span class="_ _e"> </span>features<span class="_ _a"> </span>of<span class="_ _b"> </span>objects<span class="_ _3"></span>.<span class="_ _b"> </span>Note</div><div class="t m1 x4 h7 y9c ff4 fs1 fc0 sc0 ls0 ws0">that<span class="_"> </span>shape<span class="_ _4"> </span>representations<span class="_"> </span>can<span class="_ _4"> </span>also<span class="_"> </span>be<span class="_ _4"> </span>combined<span class="_"> </span>with<span class="_ _4"> </span>the<span class="_"> </span>appearance<span class="_"> </span>representations</div><div class="t m1 x4 h7 y9d ff4 fs1 fc0 sc0 ls0 ws0">[Cootes<span class="_ _9"> </span>et<span class="_ _9"> </span>al.<span class="_ _9"> </span>2001]<span class="_ _9"> </span>for<span class="_ _b"> </span>tracking.<span class="_ _9"> </span>Some<span class="_ _9"> </span>common<span class="_ _9"> </span>appearance<span class="_ _b"> </span>representations<span class="_ _9"> </span>in<span class="_ _9"> </span>the</div><div class="t m1 x4 h7 y9e ff4 fs1 fc0 sc0 ls0 ws0">context<span class="_"> </span>of<span class="_"> </span>object<span class="_"> </span>tracking<span class="_"> </span>are:</div><div class="t m1 x4 h7 y9f ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span><span class="ff3">Probability<span class="_ _a"> </span>densities<span class="_ _a"> </span>of<span class="_ _a"> </span>object<span class="_ _a"> </span>appearance.<span class="_ _e"> </span><span class="ff4">The<span class="_ _a"> </span>probability<span class="_ _a"> </span>density<span class="_ _a"> </span>estimates<span class="_ _e"> </span>of<span class="_ _a"> </span>the</span></span></div><div class="t m1 x5 h7 ya0 ff4 fs1 fc0 sc0 ls0 ws0">object<span class="_"> </span>appearance<span class="_"> </span>can<span class="_"> </span>either<span class="_ _4"> </span>be<span class="_"> </span>parametric,<span class="_ _4"> </span>such<span class="_"> </span>as<span class="_"> </span>Gaussian<span class="_"> </span>[Zhu<span class="_ _4"> </span>and<span class="_"> </span>Y<span class="_ _f"></span>uille<span class="_"> </span>1996]</div><div class="t m1 x5 h7 ya1 ff4 fs1 fc0 sc0 ls0 ws0">and<span class="_"> </span>a<span class="_"> </span>mixture<span class="_"> </span>of<span class="_"> </span>Gaussians<span class="_"> </span>[Paragios<span class="_"> </span>and<span class="_"> </span>Deriche<span class="_"> </span>2002],<span class="_"> </span>or<span class="_"> </span>nonparametric<span class="_ _1"></span>,<span class="_"> </span>such<span class="_"> </span>as</div><div class="t m1 x5 h7 ya2 ff4 fs1 fc0 sc0 ls0 ws0">P<span class="_ _3"></span>arzen<span class="_"> </span>windows<span class="_ _8"> </span>[Elgammal<span class="_ _4"> </span>et<span class="_ _8"> </span>al.<span class="_"> </span>2002]<span class="_ _8"> </span>and<span class="_ _4"> </span>histograms<span class="_ _8"> </span>[Comaniciu<span class="_"> </span>et<span class="_ _8"> </span>al.<span class="_ _8"> </span>2003].<span class="_"> </span>The</div><div class="t m1 x5 h7 ya3 ff4 fs1 fc0 sc0 ls0 ws0">probability<span class="_ _6"> </span>densities<span class="_ _e"> </span>of<span class="_ _e"> </span>object<span class="_ _e"> </span>appearance<span class="_ _e"> </span>features<span class="_ _e"> </span>(color<span class="_ _0"></span>,<span class="_ _e"> </span>texture)<span class="_ _e"> </span>can<span class="_ _e"> </span>be<span class="_ _e"> </span>computed</div><div class="t m1 x5 h7 ya4 ff4 fs1 fc0 sc0 ls0 ws0">from<span class="_"> </span>the<span class="_ _8"> </span>image<span class="_"> </span>regions<span class="_"> </span>specified<span class="_ _4"> </span>by<span class="_"> </span>the<span class="_ _4"> </span>shape<span class="_"> </span>models<span class="_ _8"> </span>(interior<span class="_"> </span>region<span class="_"> </span>of<span class="_ _4"> </span>an<span class="_"> </span>ellipse<span class="_ _8"> </span>or</div><div class="t m1 x5 h7 ya5 ff4 fs1 fc0 sc0 ls0 ws0">a<span class="_"> </span>contour).</div><div class="t m1 x4 h7 ya6 ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span><span class="ff3">T<span class="_ _3"></span>emplates<span class="_ _3"></span>.<span class="_ _14"> </span><span class="ff4">T<span class="_ _3"></span>emplates<span class="_ _14"> </span>are<span class="_ _13"> </span>formed<span class="_ _14"> </span>using<span class="_ _14"> </span>simple<span class="_ _13"> </span>geometric<span class="_ _14"> </span>shapes<span class="_ _13"> </span>or<span class="_ _14"> </span>silhouettes</span></span></div><div class="t m1 x5 h7 ya7 ff4 fs1 fc0 sc0 ls0 ws0">[Fieguth<span class="_ _6"> </span>and<span class="_ _e"> </span>T<span class="_ _1"></span>erzopoulos<span class="_ _e"> </span>1997].<span class="_ _e"> </span>An<span class="_ _e"> </span>advantage<span class="_ _e"> </span>of<span class="_ _e"> </span>a<span class="_ _a"> </span>template<span class="_ _e"> </span>is<span class="_ _e"> </span>that<span class="_ _e"> </span>it<span class="_ _e"> </span>carries<span class="_ _e"> </span>both</div><div class="t m1 x5 h7 ya8 ff4 fs1 fc0 sc0 ls0 ws0">spatial<span class="_"> </span>and<span class="_"> </span>appearance<span class="_ _6"> </span>information.<span class="_"> </span>T<span class="_ _3"></span>emplates,<span class="_"> </span>however<span class="_ _f"></span>,<span class="_ _6"> </span>only<span class="_"> </span>encode<span class="_ _6"> </span>the<span class="_"> </span>object<span class="_"> </span>ap-</div><div class="t m1 x5 h7 ya9 ff4 fs1 fc0 sc0 ls0 ws0">pearance<span class="_ _9"> </span>generated<span class="_ _b"> </span>from<span class="_ _9"> </span>a<span class="_ _9"> </span>single<span class="_ _9"> </span>view<span class="_ _f"></span>.<span class="_ _b"> </span>Thus,<span class="_ _b"> </span>they<span class="_ _9"> </span>are<span class="_ _9"> </span>only<span class="_ _9"> </span>suitable<span class="_ _b"> </span>for<span class="_ _9"> </span>tracking</div><div class="t m1 x5 h7 yaa ff4 fs1 fc0 sc0 ls0 ws0">objects<span class="_"> </span>whose<span class="_"> </span>poses<span class="_"> </span>do<span class="_"> </span>not<span class="_"> </span>vary<span class="_"> </span>considerably<span class="_"> </span>during<span class="_"> </span>the<span class="_"> </span>course<span class="_"> </span>of<span class="_"> </span>tracking<span class="_ _1"></span>.</div><div class="t m1 x7 h6 y2c ff4 fs3 fc0 sc0 ls0 ws0">ACM<span class="_"> </span>Computing<span class="_"> </span>Surveys,<span class="_"> </span>V<span class="_ _3"></span>ol.<span class="_"> </span>38,<span class="_"> </span>No.<span class="_"> </span>4,<span class="_"> </span>Artic<span class="_ _1"></span>le<span class="_"> </span>13,<span class="_"> </span>Publication<span class="_"> </span>date:<span class="_"> </span>December<span class="_"> </span>2006.</div></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div>
<div id="pf5" class="pf w0 h0" data-page-no="5"><div class="pc pc5 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6258e36bbe9ad24cfaacba87/bg5.jpg"><div class="t m1 x1 h7 y2d ff3 fs1 fc0 sc0 ls0 ws0">Object<span class="_"> </span>T<span class="_ _3"></span>racking:<span class="_"> </span>A<span class="_"> </span>Survey<span class="_ _12"> </span><span class="ff4">5</span></div><div class="t m1 x1 h7 y5d ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span><span class="ff3">Active<span class="_ _b"> </span>appearance<span class="_ _b"> </span>models<span class="_ _3"></span>.<span class="_ _b"> </span><span class="ff4">Active<span class="_ _b"> </span>appearance<span class="_ _b"> </span>models<span class="_ _b"> </span>are<span class="_ _b"> </span>generated<span class="_ _b"> </span>by<span class="_ _b"> </span>simultane-</span></span></div><div class="t m1 x9 h7 y5e ff4 fs1 fc0 sc0 ls0 ws0">ously<span class="_ _e"> </span>modeling<span class="_ _e"> </span>the<span class="_ _e"> </span>object<span class="_ _e"> </span>shape<span class="_ _e"> </span>and<span class="_ _e"> </span>appearance<span class="_ _a"> </span>[Edwards<span class="_ _6"> </span>et<span class="_ _e"> </span>al.<span class="_ _e"> </span>1998].<span class="_ _e"> </span>In<span class="_ _a"> </span>general,</div><div class="t m1 x9 h7 y5f ff4 fs1 fc0 sc0 ls0 ws0">the<span class="_ _4"> </span>object<span class="_ _4"> </span>shape<span class="_ _4"> </span>is<span class="_ _4"> </span>defined<span class="_ _4"> </span>by<span class="_ _4"> </span>a<span class="_ _4"> </span>set<span class="_ _4"> </span>of<span class="_ _8"> </span>landmarks.<span class="_ _4"> </span>Similar<span class="_ _4"> </span>to<span class="_ _4"> </span>the<span class="_ _4"> </span>contour<span class="_ _3"></span>-based<span class="_"> </span>repre-</div><div class="t m1 x9 h7 y60 ff4 fs1 fc0 sc0 ls0 ws0">sentation,<span class="_ _8"> </span>the<span class="_ _8"> </span>landmarks<span class="_ _8"> </span>can<span class="_ _8"> </span>reside<span class="_ _8"> </span>on<span class="_ _8"> </span>the<span class="_ _8"> </span>object<span class="_ _5"> </span>boundary<span class="_ _8"> </span>or<span class="_ _0"></span>,<span class="_ _8"> </span>alternatively<span class="_ _f"></span>,<span class="_ _8"> </span>they<span class="_ _8"> </span>can</div><div class="t m1 x9 h7 y61 ff4 fs1 fc0 sc0 ls0 ws0">reside<span class="_ _a"> </span>inside<span class="_ _a"> </span>the<span class="_ _a"> </span>object<span class="_ _a"> </span>region.<span class="_ _a"> </span>F<span class="_ _3"></span>or<span class="_ _b"> </span>each<span class="_ _e"> </span>landmark,<span class="_ _a"> </span>an<span class="_ _a"> </span>appearance<span class="_ _a"> </span>vector<span class="_ _b"> </span>is<span class="_ _e"> </span>stored</div><div class="t m1 x9 h7 y62 ff4 fs1 fc0 sc0 ls0 ws0">which<span class="_ _9"> </span>is<span class="_ _9"> </span>in<span class="_ _9"> </span>the<span class="_ _9"> </span>form<span class="_ _9"> </span>of<span class="_ _9"> </span>color<span class="_ _0"></span>,<span class="_ _9"> </span>texture,<span class="_ _9"> </span>or<span class="_ _9"> </span>gradient<span class="_ _9"> </span>magnitude.<span class="_ _9"> </span>Active<span class="_ _9"> </span>appearance</div><div class="t m1 x9 h7 y63 ff4 fs1 fc0 sc0 ls0 ws0">models<span class="_ _b"> </span>require<span class="_ _b"> </span>a<span class="_ _b"> </span>training<span class="_ _b"> </span>phase<span class="_ _b"> </span>where<span class="_ _b"> </span>both<span class="_ _b"> </span>the<span class="_ _b"> </span>shape<span class="_ _b"> </span>and<span class="_ _b"> </span>its<span class="_ _b"> </span>associated<span class="_ _b"> </span>appear-</div><div class="t m1 x9 h7 y64 ff4 fs1 fc0 sc0 ls0 ws0">ance<span class="_ _a"> </span>is<span class="_ _a"> </span>learned<span class="_ _b"> </span>from<span class="_ _e"> </span>a<span class="_ _b"> </span>set<span class="_ _e"> </span>of<span class="_ _b"> </span>samples<span class="_ _a"> </span>using,<span class="_ _e"> </span>for<span class="_ _a"> </span>instance,<span class="_ _a"> </span>the<span class="_ _a"> </span>principal<span class="_ _b"> </span>component</div><div class="t m1 x9 h7 y65 ff4 fs1 fc0 sc0 ls0 ws0">analysis.</div><div class="t m1 x1 h7 yab ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span><span class="ff3">Multiview<span class="_"> </span>appearance<span class="_ _8"> </span>models<span class="_ _1"></span>.<span class="_"> </span><span class="ff4">These<span class="_ _8"> </span>models<span class="_"> </span>encode<span class="_ _8"> </span>different<span class="_"> </span>views<span class="_ _4"> </span>of<span class="_ _4"> </span>an<span class="_"> </span>object.<span class="_ _8"> </span>One</span></span></div><div class="t m1 x9 h7 yac ff4 fs1 fc0 sc0 ls0 ws0">approach<span class="_ _6"> </span>to<span class="_ _e"> </span>represent<span class="_ _e"> </span>the<span class="_ _e"> </span>different<span class="_ _6"> </span>object<span class="_ _e"> </span>views<span class="_ _e"> </span>is<span class="_ _e"> </span>to<span class="_ _e"> </span>generate<span class="_ _e"> </span>a<span class="_ _e"> </span>subspace<span class="_ _6"> </span>from<span class="_ _e"> </span>the</div><div class="t m1 x9 h7 yad ff4 fs1 fc0 sc0 ls0 ws0">given<span class="_ _8"> </span>views<span class="_ _3"></span>.<span class="_ _8"> </span>Subspace<span class="_ _8"> </span>approaches<span class="_ _3"></span>,<span class="_ _8"> </span>for<span class="_ _8"> </span>example,<span class="_ _5"> </span>Principal<span class="_ _8"> </span>Component<span class="_ _8"> </span>Analysis<span class="_ _5"> </span>(PCA)</div><div class="t m1 x9 h7 yae ff4 fs1 fc0 sc0 ls0 ws0">and<span class="_ _9"> </span>Independent<span class="_ _b"> </span>Component<span class="_ _9"> </span>Analysis<span class="_ _9"> </span>(ICA),<span class="_ _b"> </span>have<span class="_ _9"> </span>been<span class="_ _9"> </span>used<span class="_ _b"> </span>for<span class="_ _9"> </span>both<span class="_ _9"> </span>shape<span class="_ _b"> </span>and</div><div class="t m1 x9 h7 yaf ff4 fs1 fc0 sc0 ls0 ws0">appearance<span class="_ _8"> </span>representation<span class="_"> </span>[Mughadam<span class="_ _8"> </span>and<span class="_ _8"> </span>Pentland<span class="_ _8"> </span>1997;<span class="_ _4"> </span>Black<span class="_ _8"> </span>and<span class="_ _4"> </span>Jepson<span class="_ _8"> </span>1998].</div><div class="t m1 x8 h7 yb0 ff4 fs1 fc0 sc0 ls0 ws0">Another<span class="_ _4"> </span>approach<span class="_ _4"> </span>to<span class="_ _4"> </span>learn<span class="_ _4"> </span>the<span class="_ _4"> </span>different<span class="_ _4"> </span>views<span class="_ _4"> </span>of<span class="_ _4"> </span>an<span class="_ _4"> </span>object<span class="_ _4"> </span>is<span class="_"> </span>by<span class="_ _8"> </span>training<span class="_"> </span>a<span class="_ _8"> </span>set<span class="_"> </span>of<span class="_ _8"> </span>clas-</div><div class="t m1 x1 h7 yb1 ff4 fs1 fc0 sc0 ls0 ws0">sifiers,<span class="_"> </span>for<span class="_"> </span>example,<span class="_"> </span>the<span class="_ _6"> </span>support<span class="_"> </span>vector<span class="_ _6"> </span>machines<span class="_"> </span>[Avidan<span class="_"> </span>2001]<span class="_"> </span>or<span class="_ _6"> </span>Bayesian<span class="_"> </span>networks</div><div class="t m1 x1 h7 yb2 ff4 fs1 fc0 sc0 ls0 ws0">[P<span class="_ _3"></span>ark<span class="_"> </span>and<span class="_"> </span>Aggarwal<span class="_"> </span>2004].<span class="_"> </span>One<span class="_"> </span>limitation<span class="_"> </span>of<span class="_"> </span>multiview<span class="_"> </span>appearance<span class="_"> </span>models<span class="_ _4"> </span>is<span class="_"> </span>that<span class="_"> </span>the</div><div class="t m1 x1 h7 yb3 ff4 fs1 fc0 sc0 ls0 ws0">appearances<span class="_"> </span>in<span class="_"> </span>all<span class="_"> </span>views<span class="_"> </span>are<span class="_"> </span>required<span class="_"> </span>ahead<span class="_"> </span>of<span class="_"> </span>time.</div><div class="t m1 x8 h7 yb4 ff4 fs1 fc0 sc0 ls0 ws0">In<span class="_ _4"> </span>general,<span class="_"> </span>there<span class="_ _8"> </span>is<span class="_"> </span>a<span class="_ _8"> </span>strong<span class="_"> </span>relationship<span class="_ _8"> </span>between<span class="_"> </span>the<span class="_ _8"> </span>object<span class="_"> </span>representations<span class="_ _4"> </span>and<span class="_ _4"> </span>the</div><div class="t m1 x1 h7 yb5 ff4 fs1 fc0 sc0 ls0 ws0">tracking<span class="_ _b"> </span>algorithms<span class="_ _3"></span>.<span class="_ _b"> </span>Object<span class="_ _b"> </span>representations<span class="_ _b"> </span>are<span class="_ _b"> </span>usually<span class="_ _b"> </span>chosen<span class="_ _b"> </span>according<span class="_ _b"> </span>to<span class="_ _a"> </span>the<span class="_ _b"> </span>ap-</div><div class="t m1 x1 h7 yb6 ff4 fs1 fc0 sc0 ls0 ws0">plication<span class="_ _b"> </span>domain.<span class="_ _9"> </span>F<span class="_ _3"></span>or<span class="_ _b"> </span>tracking<span class="_ _b"> </span>objects,<span class="_ _b"> </span>which<span class="_ _9"> </span>appear<span class="_ _b"> </span>very<span class="_ _b"> </span>small<span class="_ _9"> </span>in<span class="_ _b"> </span>an<span class="_ _b"> </span>image,<span class="_ _b"> </span>point</div><div class="t m1 x1 h7 yb7 ff4 fs1 fc0 sc0 ls0 ws0">representation<span class="_ _9"> </span>is<span class="_ _9"> </span>usually<span class="_ _9"> </span>appropriate.<span class="_ _9"> </span>F<span class="_ _3"></span>or<span class="_ _9"> </span>instance,<span class="_ _9"> </span>V<span class="_ _0"></span>eenman<span class="_ _9"> </span>et<span class="_ _9"> </span>al.<span class="_ _9"> </span>[2001]<span class="_ _9"> </span>use<span class="_ _9"> </span>the</div><div class="t m1 x1 h7 yb8 ff4 fs1 fc0 sc0 ls0 ws0">point<span class="_"> </span>representation<span class="_"> </span>to<span class="_"> </span>track<span class="_"> </span>the<span class="_ _4"> </span>seeds<span class="_"> </span>in<span class="_"> </span>a<span class="_"> </span>moving<span class="_"> </span>dish<span class="_"> </span>sequence<span class="_ _3"></span>.<span class="_"> </span>Similarly<span class="_ _f"></span>,<span class="_"> </span>Shafique</div><div class="t m1 x1 h7 yb9 ff4 fs1 fc0 sc0 ls0 ws0">and<span class="_ _a"> </span>Shah<span class="_ _b"> </span>[2003]<span class="_ _a"> </span>use<span class="_ _b"> </span>the<span class="_ _a"> </span>point<span class="_ _b"> </span>representation<span class="_ _a"> </span>to<span class="_ _b"> </span>track<span class="_ _a"> </span>distant<span class="_ _b"> </span>birds<span class="_ _1"></span>.<span class="_ _a"> </span>F<span class="_ _3"></span>or<span class="_ _b"> </span>the<span class="_ _a"> </span>objects</div><div class="t m1 x1 h7 yba ff4 fs1 fc0 sc0 ls0 ws0">whose<span class="_ _8"> </span>shapes<span class="_ _8"> </span>can<span class="_ _4"> </span>be<span class="_ _8"> </span>approximated<span class="_ _8"> </span>by<span class="_ _4"> </span>rectangles<span class="_ _8"> </span>or<span class="_ _8"> </span>ellipses,<span class="_ _8"> </span>primitive<span class="_ _8"> </span>geometric<span class="_ _4"> </span>shape</div><div class="t m1 x1 h7 ybb ff4 fs1 fc0 sc0 ls0 ws0">representations<span class="_ _6"> </span>are<span class="_ _6"> </span>more<span class="_ _6"> </span>appropriate.<span class="_ _6"> </span>Comaniciu<span class="_ _6"> </span>et<span class="_ _e"> </span>al.<span class="_ _6"> </span>[2003]<span class="_ _6"> </span>use<span class="_ _e"> </span>an<span class="_ _6"> </span>elliptical<span class="_ _6"> </span>shape</div><div class="t m1 x1 h7 ybc ff4 fs1 fc0 sc0 ls0 ws0">representation<span class="_ _a"> </span>and<span class="_ _a"> </span>employ<span class="_ _a"> </span>a<span class="_ _a"> </span>color<span class="_ _a"> </span>histogram<span class="_ _a"> </span>computed<span class="_ _a"> </span>from<span class="_ _a"> </span>the<span class="_ _a"> </span>elliptical<span class="_ _a"> </span>region<span class="_ _a"> </span>for</div><div class="t m1 x1 h7 ybd ff4 fs1 fc0 sc0 ls0 ws0">modeling<span class="_ _8"> </span>the<span class="_ _8"> </span>appearance<span class="_ _1"></span>.<span class="_ _8"> </span>In<span class="_ _5"> </span>1998,<span class="_ _8"> </span>Black<span class="_ _8"> </span>and<span class="_ _8"> </span>J<span class="_ _1"></span>epson<span class="_ _8"> </span>used<span class="_ _5"> </span>eigenvectors<span class="_ _8"> </span>to<span class="_ _8"> </span>represent<span class="_ _8"> </span>the</div><div class="t m1 x1 h7 ybe ff4 fs1 fc0 sc0 ls0 ws0">appearance.<span class="_ _6"> </span>The<span class="_ _e"> </span>eigenvectors<span class="_ _a"> </span>were<span class="_ _e"> </span>generated<span class="_ _e"> </span>from<span class="_ _e"> </span>rectangular<span class="_ _a"> </span>object<span class="_ _e"> </span>templates.<span class="_ _6"> </span>F<span class="_ _3"></span>or</div><div class="t m1 x1 h7 ybf ff4 fs1 fc0 sc0 ls0 ws0">tracking<span class="_"> </span>objects<span class="_"> </span>with<span class="_"> </span>complex<span class="_"> </span>shapes,<span class="_"> </span>for<span class="_"> </span>example,<span class="_"> </span>humans<span class="_ _1"></span>,<span class="_"> </span>a<span class="_"> </span>contour<span class="_"> </span>or<span class="_ _6"> </span>a<span class="_"> </span>silhouette-</div><div class="t m1 x1 h7 yc0 ff4 fs1 fc0 sc0 ls0 ws0">based<span class="_"> </span>representation<span class="_"> </span>is<span class="_"> </span>appropriate.<span class="_"> </span>Haritaoglu<span class="_"> </span>et<span class="_"> </span>al.<span class="_"> </span>[2000]<span class="_"> </span>use<span class="_ _6"> </span>silhouettes<span class="_"> </span>for<span class="_"> </span>object</div><div class="t m1 x1 h7 yc1 ff4 fs1 fc0 sc0 ls0 ws0">tracking<span class="_"> </span>in<span class="_"> </span>a<span class="_"> </span>surveillance<span class="_"> </span>application.</div><div class="t m1 x1 h8 yc2 ff1 fs4 fc0 sc0 ls0 ws0">3.<span class="_ _9"> </span>FEA<span class="_ _0"></span>TURE<span class="_"> </span>SELECTION<span class="_"> </span>FOR<span class="_"> </span>TRACKING</div><div class="t m1 x1 h7 yc3 ff4 fs1 fc0 sc0 ls0 ws0">Selecting<span class="_ _e"> </span>the<span class="_ _a"> </span>right<span class="_ _e"> </span>features<span class="_ _a"> </span>plays<span class="_ _e"> </span>a<span class="_ _a"> </span>critical<span class="_ _e"> </span>role<span class="_ _a"> </span>in<span class="_ _e"> </span>tracking.<span class="_ _e"> </span>In<span class="_ _e"> </span>general,<span class="_ _a"> </span>the<span class="_ _e"> </span>most<span class="_ _a"> </span>de-</div><div class="t m1 x1 h7 yc4 ff4 fs1 fc0 sc0 ls0 ws0">sirable<span class="_ _6"> </span>property<span class="_ _e"> </span>of<span class="_ _e"> </span>a<span class="_ _e"> </span>visual<span class="_ _6"> </span>feature<span class="_ _e"> </span>is<span class="_ _e"> </span>its<span class="_ _e"> </span>uniqueness<span class="_ _e"> </span>so<span class="_ _6"> </span>that<span class="_ _e"> </span>the<span class="_ _e"> </span>objects<span class="_ _e"> </span>can<span class="_ _e"> </span>be<span class="_ _6"> </span>easily</div><div class="t m1 x1 h7 yc5 ff4 fs1 fc0 sc0 ls0 ws0">distinguished<span class="_ _8"> </span>in<span class="_"> </span>the<span class="_ _8"> </span>feature<span class="_ _8"> </span>space.<span class="_ _8"> </span>F<span class="_ _3"></span>eature<span class="_"> </span>selection<span class="_ _8"> </span>is<span class="_ _8"> </span>closely<span class="_ _8"> </span>related<span class="_"> </span>to<span class="_ _8"> </span>the<span class="_ _8"> </span>object<span class="_"> </span>rep-</div><div class="t m1 x1 h7 yc6 ff4 fs1 fc0 sc0 ls0 ws0">resentation.<span class="_ _a"> </span>F<span class="_ _3"></span>or<span class="_ _b"> </span>example<span class="_ _1"></span>,<span class="_ _a"> </span>color<span class="_ _a"> </span>is<span class="_ _b"> </span>used<span class="_ _a"> </span>as<span class="_ _a"> </span>a<span class="_ _b"> </span>feature<span class="_ _a"> </span>for<span class="_ _a"> </span>histogram-based<span class="_ _a"> </span>appearance</div><div class="t m1 x1 h7 yc7 ff4 fs1 fc0 sc0 ls0 ws0">representations<span class="_ _1"></span>,<span class="_"> </span>while<span class="_"> </span>for<span class="_"> </span>contour<span class="_ _3"></span>-based<span class="_"> </span>representation,<span class="_"> </span>object<span class="_"> </span>edges<span class="_"> </span>are<span class="_"> </span>usually<span class="_"> </span>used</div><div class="t m1 x1 h7 yc8 ff4 fs1 fc0 sc0 ls0 ws0">as<span class="_"> </span>features<span class="_ _3"></span>.<span class="_"> </span>In<span class="_"> </span>general,<span class="_ _8"> </span>many<span class="_"> </span>tracking<span class="_"> </span>algorithms<span class="_ _8"> </span>use<span class="_"> </span>a<span class="_"> </span>combination<span class="_ _4"> </span>of<span class="_"> </span>these<span class="_ _8"> </span>features.</div><div class="t m1 x1 h7 yc9 ff4 fs1 fc0 sc0 ls0 ws0">The<span class="_"> </span>details<span class="_"> </span>of<span class="_"> </span>common<span class="_"> </span>visual<span class="_"> </span>features<span class="_"> </span>are<span class="_"> </span>as<span class="_"> </span>follows.</div><div class="t m1 x1 h7 yca ff4 fs1 fc0 sc0 ls0 ws0">—<span class="_ _0"></span><span class="ff3">Color<span class="_ _f"></span>.<span class="_"> </span><span class="ff4">The<span class="_ _8"> </span>apparent<span class="_"> </span>color<span class="_ _8"> </span>of<span class="_"> </span>an<span class="_ _4"> </span>object<span class="_ _4"> </span>is<span class="_ _4"> </span>influenced<span class="_"> </span>primarily<span class="_ _8"> </span>by<span class="_"> </span>two<span class="_ _8"> </span>physical<span class="_"> </span>factors<span class="_ _3"></span>,</span></span></div><div class="t m1 x9 h7 ycb ff4 fs1 fc0 sc0 ls0 ws0">1)<span class="_ _b"> </span>the<span class="_ _a"> </span>spectral<span class="_ _b"> </span>power<span class="_ _b"> </span>distribution<span class="_ _a"> </span>of<span class="_ _b"> </span>the<span class="_ _a"> </span>illuminant<span class="_ _b"> </span>and<span class="_ _b"> </span>2)<span class="_ _a"> </span>the<span class="_ _b"> </span>surface<span class="_ _b"> </span>reflectance</div><div class="t m1 x9 h7 ycc ff4 fs1 fc0 sc0 ls0 ws0">properties<span class="_ _6"> </span>of<span class="_ _6"> </span>the<span class="_ _6"> </span>object.<span class="_ _6"> </span>In<span class="_ _6"> </span>image<span class="_ _6"> </span>processing,<span class="_"> </span>the<span class="_ _6"> </span>RGB<span class="_ _6"> </span>(red,<span class="_ _6"> </span>green,<span class="_ _6"> </span>blue)<span class="_ _6"> </span>color<span class="_ _6"> </span>space</div><div class="t m1 x9 h7 ycd ff4 fs1 fc0 sc0 ls0 ws0">is<span class="_"> </span>usually<span class="_ _4"> </span>used<span class="_"> </span>to<span class="_ _8"> </span>represent<span class="_"> </span>color<span class="_ _0"></span>.<span class="_"> </span>However<span class="_ _f"></span>,<span class="_"> </span>the<span class="_"> </span>RGB<span class="_ _8"> </span>space<span class="_"> </span>is<span class="_"> </span>not<span class="_ _4"> </span>a<span class="_"> </span>perceptually<span class="_ _4"> </span>uni-</div><div class="t m1 x9 h7 yce ff4 fs1 fc0 sc0 ls0 ws0">form<span class="_"> </span>color<span class="_"> </span>space,<span class="_"> </span>that<span class="_"> </span>is,<span class="_"> </span>the<span class="_"> </span>differences<span class="_"> </span>between<span class="_"> </span>the<span class="_"> </span>colors<span class="_"> </span>in<span class="_"> </span>the<span class="_ _6"> </span>RGB<span class="_"> </span>space<span class="_"> </span>do<span class="_"> </span>not</div><div class="t m1 x9 h7 ycf ff4 fs1 fc0 sc0 ls0 ws0">correspond<span class="_ _a"> </span>to<span class="_ _a"> </span>the<span class="_ _a"> </span>color<span class="_ _b"> </span>differences<span class="_ _e"> </span>perceived<span class="_ _b"> </span>by<span class="_ _e"> </span>humans<span class="_ _b"> </span>[P<span class="_ _3"></span>aschos<span class="_ _a"> </span>2001].<span class="_ _a"> </span>Addition-</div><div class="t m1 x9 h7 yd0 ff4 fs1 fc0 sc0 ls0 ws0">ally<span class="_ _f"></span>,<span class="_ _6"> </span>the<span class="_ _e"> </span>RGB<span class="_ _e"> </span>dimensions<span class="_ _e"> </span>are<span class="_ _e"> </span>highly<span class="_ _e"> </span>correlated.<span class="_ _e"> </span>In<span class="_ _6"> </span>contrast,<span class="_ _b"> </span><span class="ff3">L</span></div><div class="t m1 xb h9 yd1 ff6 fs3 fc0 sc0 ls0 ws0">∗</div><div class="t m1 xc ha yd2 ff3 fs1 fc0 sc0 ls0 ws0">u</div><div class="t m1 xd h9 yd1 ff6 fs3 fc0 sc0 ls0 ws0">∗</div><div class="t m1 xe ha yd2 ff3 fs1 fc0 sc0 ls0 ws0">v</div><div class="t m1 xf h9 yd1 ff6 fs3 fc0 sc0 ls0 ws0">∗</div><div class="t m1 x10 h7 yd2 ff4 fs1 fc0 sc0 ls0 ws0">and<span class="_ _b"> </span><span class="ff3">L</span></div><div class="t m1 x11 h9 yd1 ff6 fs3 fc0 sc0 ls0 ws0">∗</div><div class="t m1 x12 ha yd2 ff3 fs1 fc0 sc0 ls0 ws0">a</div><div class="t m1 x13 h9 yd1 ff6 fs3 fc0 sc0 ls0 ws0">∗</div><div class="t m1 x14 ha yd2 ff3 fs1 fc0 sc0 ls0 ws0">b</div><div class="t m1 x15 h9 yd1 ff6 fs3 fc0 sc0 ls0 ws0">∗</div><div class="t m1 x16 h7 yd2 ff4 fs1 fc0 sc0 ls0 ws0">are</div><div class="t m1 x9 h7 yd3 ff4 fs1 fc0 sc0 ls0 ws0">perceptually<span class="_"> </span>uniform<span class="_ _8"> </span>color<span class="_"> </span>spaces<span class="_ _1"></span>,<span class="_"> </span>while<span class="_ _8"> </span>HSV<span class="_"> </span>(Hue,<span class="_ _8"> </span>Saturation,<span class="_"> </span>V<span class="_ _0"></span>alue)<span class="_"> </span>is<span class="_ _4"> </span>an<span class="_"> </span>approx-</div><div class="t m1 x9 h7 yd4 ff4 fs1 fc0 sc0 ls0 ws0">imately<span class="_"> </span>uniform<span class="_ _8"> </span>color<span class="_"> </span>space<span class="_ _1"></span>.<span class="_"> </span>However<span class="_ _f"></span>,<span class="_"> </span>these<span class="_ _8"> </span>color<span class="_"> </span>spaces<span class="_ _4"> </span>are<span class="_"> </span>sensitive<span class="_ _8"> </span>to<span class="_"> </span>noise<span class="_ _4"> </span>[Song</div><div class="t m1 x1 h6 y2c ff4 fs3 fc0 sc0 ls0 ws0">ACM<span class="_"> </span>Computing<span class="_"> </span>Surveys,<span class="_"> </span>V<span class="_ _3"></span>ol.<span class="_"> </span>38,<span class="_"> </span>No.<span class="_"> </span>4,<span class="_"> </span>Artic<span class="_ _1"></span>le<span class="_"> </span>13,<span class="_"> </span>Publication<span class="_"> </span>date:<span class="_"> </span>December<span class="_"> </span>2006.</div></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div>