Bi-label Propagation for Generic Multiple Object Tracking

Transcription

1 Bi-label Propagaion for Generic Muliple Objec Tracking Wenhan Luo, Tae-Kyun Kim, Björn Senger 2, Xiaowei Zhao, Robero Cipolla 3 Imperial College London, 2 Toshiba Research Europe, 3 Universiy of Cambridge {w.luo2,k.kim,x.zhao}@imperial.ac.uk, [email protected], [email protected] Absrac In his paper, we propose a label propagaion framework o handle he muliple objec racking (MOT) problem for a generic objec ype (cf. pedesrian racking). Given a arge objec by an iniial bounding box, all objecs of he same ype are localized ogeher wih heir ideniies. We rea his as a problem of propagaing bi-labels, i.e. a binary class label for deecion and individual objec labels for racking. To propagae he class label, we adop clusered Muliple Task Learning (cmtl) while enforcing spaio-emporal consisency and show ha his improves he performance when given limied raining daa. To rack objecs, we propagae labels from rajecories o deecions based on affiniy using appearance, moion, and conex. Experimens on public and challenging new sequences show ha he proposed mehod improves over he curren sae of he ar on his ask.. Inroducion Muliple Objec Tracking (MOT) plays an imporan role in he compuer vision lieraure. The problem is difficul due o frequen occlusions and appearance similariy beween objecs. Owing o advances in objec deecion (especially in pedesrian deecion [9, ]), in some cases he ask can be solved efficienly using a racking-as-deecion approach. However, generalizing he ask o oher objecs (see our daa ses in Sec. 4) would require raining a deecor for each new objec ype, which is impracical. In his paper we deal wih he problem of racking muliple objecs of he same generic ype given only one iniial bounding box [8], and our ask is o recover muliple rajecories from image observaions. Treaing sliding windows as poins in a spaio-emporal cuboid and he iniial bounding box as a single labeled poin, we aim o discover and rack new objecs by propagaing labels o similar candidaes. From his perspecive, our problem shares grea similariy wih semanic video segmenaion [3] which aims o label all he pixels in a video given pixel labels in he firs frame. However, hese wo problems have significan dif + Figure : The proposed framework. Yellow arrows indicae he propagaion of class labels wihin he same frame and whie arrows indicae objec label propagaion over ime (bes viewed in color). ferences: labels in video segmenaion involve only a fixed number of pre-defined classes, whereas labels in our problem involve boh binary classes (objec vs. background) and muliple classes (specific objec ideniies). Thus he number of classes in our problem varies as objecs appear or disappear. Also, in video segmenaion more han one pixel can share he same label while in our case objec labels are exclusive. We rea he labels as a combinaion of binary class labels and objec labels (ideniies), and we refer o deecion responses as an inermediae layer beween image observaions and rajecory esimaions. Furhermore, we propose a sequenial label propagaion framework (Fig. ) o propagae class labels and objec labels in boh spaial and emporal domains. This so called bi-label propagaion framework coincides wih a racking-by-deecion sraegy: hrough spaially propagaing he class labels (yellow arrows in Fig. ), we solve he deecion problem, discovering he appearance and disappearance of objecs; by emporally propagaing objec labels (whie arrows in Fig. ), we ackle he muli-objec racking problem. Learning a robus deecor from a single raining insance is challenging and sandard mehods end o eiher overfi (e.g. using a kernel Suppor Vecor Machine (SVM)) or underfi (e.g. using a linear SVM). To address he generalizaion issue, we rain muliple deecors inspired by ensemble learning. Muliple deecors are inherenly relaed o each oher since hey are dealing wih he same ype of objecs.

2 The moivaion of Muliple Task Learning (MTL) [0] is o learn muliple relaed asks simulaneously raher han independenly. Thus, we rea raining each of he deecors as one ask and adop clusered MTL (cmtl) [32] o regularize he raining process of muliple deecors. In addiion, we assume ha images and hence deecion resuls do no change drasically from frame o frame. We model his spaio-emporal consisency by inegraing i ino he cmtl formula during he class label propagaion. Our key conribuions are () proposing a probabilisic framework for joinly propagaing class and objec labels in spaial and emporal domains for generic MOT and (2) inroducing cmtl for generic objec deecion and improving i by considering he spaio-emporal consisency. 2. Relaed work MOT mehods can be grouped ino wo caegories [23]: sequenial (or online) approaches, which oupu rajecories on he fly, and bach (or off-line) approaches, which oupu resuls afer processing all frames. Sequenial approaches derive a cos funcion and esimae he lowes cos sae based on sophisicaed appearance, moion and ineracion models. For example, o mainain discriminaion of individual objecs, Yang e al. [29] fuse muliple componens: bags of local feaures, a head model, and a color model of orso regions. In [6], generic objec caegory and insance-specific informaion are inegraed o rack muliple objecs in a paricle filer framework. Inspired by crowd simulaion models, a dynamic model considering social moion paerns is inroduced in [2]. Similarly, Yamaguchi e al. [27] develop an agen-based behavior model aking social and environmenal facors ino accoun o predic desinaions of pedesrians. The work in [4] esimaes objec moion based on srucured crowd paerns and learns spaio-emporal variaions using a se of hidden Markov models. Bach approaches exhibi a delay in oupuing resuls, bu hey end o be more robus as hey can access all observaions simulaneously. Typical bach approaches [7, 2, 5, 28] cas he problem as a daa associaion problem, linking shor-erm observaions such as single deecion responses or rackles ino longer rajecories using mehods such as he Hungarian algorihm [25], greedy biparie maching [24], min-cos nework flow [8, 26], KShores Pahs [4], or discree-coninuous Condiional Random Fields (CRF) [9]. Mehods for generic objec deecion in video daa require eiher pre-rained deecors [30] or off-line raining []. Models are adaped o a given inpu video in order o improve he deecion accuracy, e.g. by ieraive boosing []. The closes work o ours is coupled deecion and racking [6, 26]. However, mos work assumes ha a deecor X X2 Xn Y0 Y Y2 Yn Z0 Z Z2 Zn (a) (b) Figure 2: (a) Our graphical model. (b) Top o boom: sliding windows X, deecion responses Y, and rajecories Z. For sake of display, we only show wo rajecories (bes viewed in color). is available ha has been rained off-line. For example, [26] use a dicionary of foreground images for pedesrian deecion ogeher wih background subracion. The work in [6] employs off-line rained pedesrian and car deecors. In erms of problem seing, we follow he model-free approaches in [8, 3]. The mehod of Zhang and van der Maaen requires iniializaion wih bounding boxes of all objecs and in conras o our mehod does no discover new similar objecs [3]. Luo and Kim firs rain a generic objec deecor, and subsequenly employ he deecor o regularize he raining of muliple rackers [8]. In conras o his approach, we learn deecion wih he help of racking, i.e. he spaio-emporal consisency, as well as racking based on deecion, in a join opimizaion framework. 3. Bi-label Propagaion 3.. Bayesian perspecive Le X, Y and Z represen sliding windows (image observaions), deecion responses and rajecories, respecively. Fig. 2(a) shows our graphical model which has hree layers: image observaion, deecion, and rajecory layer, respecively. The darkly shaded nodes are observed nodes, he ransparen nodes are hidden (or laen) nodes, and he lighly shaded nodes (Y0 and Z0 ) are parly observed as we are given only a single iniial bounding box in he firs frame. From he image layer o he deecion response layer we propagae class labels. From he deecion response layer o he rajecory layer we propagae objec labels. Solving our problem corresponds o maximizing P (Z X). Inroducing variable Y, we obain max P (Z X) max P (Z X, Y )P (Y X) Z Z,Y P (Z X, Y, Z0: )P (Y X, Y ), = max Z,Y ()

3 where P (Y X) models class label propagaion (deecion) and P (Z X, Y ) models objec label propagaion (racking). We expand i sequenially as max P (Z X, Y, Z 0: )P (Y X, Y ), (2) Z,Y and solve his esimaion problem by decomposiion. Taking he negaive logarihm of Eq. 2, we rewrie i as: min W,Θ L C (W ) + L O (Θ ), (3) where L C (W ) models class label propagaion, L O (Θ ) models objec label propagaion and W, Θ are parameers represening he deecor and propagaion configuraion a ime. To minimize he funcion, we () fix Θ o minimize L C via W ; (2) fix W, minimize L O via Θ ; (3) + (go o he nex frame) Class label propagaion Le us review he Bayesian formula of class label propagaion P (Y X, Y ) in Eq. 2. We wan o maximize he likelihood of Y condiioned on observaions X (spaial domain) and he previous esimaion Y (emporal domain). Our deecion problem differs from he radiional deecion problem as we do no have sufficien daa o handle large inra-class variaion. Fig. 3 illusraes he exen of inra-class variaion in hree es videos. As raining a single classifier leads o underfiing or overfiing, we rain muliple deecors and make a decision based on all of hem. Moreover, by reaing raining each deecor as one ask, we invesigae he relaionship among muliple deecors and adop clusered MTL o rain hese deecors simulaneously, improving he generalizaion abiliy. In he firs frame, we add small perurbaions o he iniial bounding box (sligh shif, roaion, scale changes) o augmen he posiive daa. Sliding windows wih an overlap (inersecion/union) of he posiive samples beween 0.2 and 0.3 are negaive samples. In he following frames, we collec confiden insances as posiive samples and augmen he raining daa in he same way. By randomly sampling a subse of insances from he whole raining daa wihou placemen m imes, we obain m ses of raining daa X l,,i R d N,i, i =,..., m and heir labels Y,i {, } N,i, where he subscrip l means labeled, d is he feaure space dimension and N,i is he number of insances. Le he muliple deecors be W = [w,..., w m ] R d m. Using he leas square error he daa cos erm is m i= XT l,,iw,i Y,i 2. The deecors are relaed as hey are dealing wih objecs of he same ype. Meanwhile, as a resul of daa disribuion a cluser of insances are more similar o each oher compared wih (a) (b) (c) Figure 3: Illusraion of inra-class variance. Shown are cropped regions from (a) he Airshow sequence, (b) he Goose sequence and (c) he Hockey sequence. ohers, e.g. some insances exhibi a similar viewpoin while some do no. Consequenly, some deecors will be closer o each oher in he model parameer space. We herefore assume ha he deecors form k clusers as C j, j =,..., k, and model he coupling among all deecors following [32]: k j= v C j w v w j 2 = r(w T W) r(f T W T WF), (4) where w j is he mean of he deecors wihin he same cluser, r( ) is he race norm, and F R m k is an orhogonal cluser indicaor marix wih F i,j = nj if i C j and F i,j = 0 oherwise. Along wih regularizaion of each deecor m i= w i 2 = r(w T W), we have a regularizaion erm r(w(( + η)i FF T )W T ), where η is a weigh parameer. Following he convex relaxaion of cmtl [32], his regularizaion erm is relaxed o r(w(ηi+m) W T ), subjec o r(m) = k, M I, M S m +, where S m + is he se of posiive semi-definie (PSD) marices and M I means I M is PSD. Tradiional MOT applies a deecor o every frame independenly. By conras, we find ha deecion responses in wo subsequen frames should no change drasically. To uilize such informaion, we rack confiden insances via a weak racker (KLT in our implemenaion) from frame o frame, and produce a densiy map P (see an example in Fig. 4(d)) by smoohing he confidence scores wih a Gaussian (σ = 5). Based on P, sliding windows X u, R d N (here he subscrip u means unlabeled ) can be weakly labeled as Ψ(P ) which is he summaion of he densiy of pixels close o heir ceners (wihin a circle of radius 4). The cos erm m m i= XT u,w,i Ψ(P ) 2 can be considered as a weakly supervised erm which propagaes labels in he emporal domain. Inuiively, i assiss he deecor o recall more insances; Fig. 4 shows his concep. Yellow boxes indicae he deecion resuls (also posiive insances), black boxes are negaive insances, and whie boxes are unlabeled samples. Wih he help of spaio-emporal consisency, some candidaes have weak labels indicaed by he orange boxes in frame shown in Fig. 4(e), and he weak labels help o recover missed deecions, see he dashed yellow box in frame in Fig. 4(f) which is a missed deecion caused by occlusion in Fig. 4(c). Based on he erms de-

4 P ȣ௧ 50 (a) (d) (b) (e) where TiA, TiM and TiC indicae appearance, moion, and conex informaion, and le he m deecion responses a ime be - (c) Figure 5: Objec labels are propagaed from rajecories (differen colors mean differen objecs) in frame o deecion responses in frame. Noe he proximiy of a flower indicaed by he black dashed circle (bes viewed in color). (f) D = {Dj Dj =< DjA, DjL, DjC >, j =,..., m}, (8) (5) where DjA, DjL and DjC represen he appearance, locaion and conex informaion. Tracking is carried ou by propagaing objec labels from rajecories o deecion responses via a configuraion variable Θ Rn m. Iniially, all he elemens of Θ are 0. If an elemen Θij is swiched o, hen he label of rajecory Ti is propagaed o deecion response Dj, and he propagaed quaniy depends on he affiniy S(Ti Dj ) beween Ti and Dj (here means considering Dj as a componen of Ti a ime ), which is deermined by appearance, moion and conex. Fig. 5 shows his process. Objecs are assumed o move smoohly, so we only consider deecion responses wihin Ti s spaioemporal proximiy Ωi (a circle wih radius dt h ) and minimize he following energy funcion: LO (Θ ) = S(Ti Dj )Θij. (9) We rea his as a join convex problem wih regard o W and M [2]. Following [32], we adop he Acceleraed Projec Gradien mehod o opimize his funcion. Labels of Xu, are obained by averaging he scores of all deecors as: Appearance Model. We simply consider he inensiy cue for appearance affiniy. The appearance model TiA of rajecory Ti consiss of he las 5 emplaes of his objec, and he appearance similariy beween Dj and Ti is - - Figure 4: Illusraion of how he spaio-emporal consisency guides he deecion procedure (bes viewed in color). scribed above, we have LC (W ) = α r(w (ηi + M ) WT ) + {z } regularizaion λ 2 m m i= XTu, w,i Ψ(P) 2 + {z } m i= XT w,i Y,i 2 2N,i l,,i {z } spaio emporal consisency loss s.. r(m ) = k, M I, M Sm + T X w,i m i= u, m Yu, = (6) We choose candidaes wih a score greaer han zero and apply non-maximum suppression o oupu final class labels Yu, {, }N Objec label propagaion In he Bayesian formula Eq. 2, objec label propagaion is P (Z X, Y, Z0: ), where he esimaion of Z is condiioned on deecion responses Y and he hisory of esimaions Z0:. Le he n rajecories a ime be T = {Ti Ti =< TiA, TiM, TiC >, i =,..., n}, (7) i j Ωi SA (Ti Dj ) = med(ncc(tia, DjA )), (0) where NCC(, ) is he normalized cross-correlaion (NCC) similariy measure and med( ) is he median. Moion Model. We mainain he pas hree displacemens and predic a displacemen veci weighed by [ 47, 27, 7 ], where older values are weighed higher. Given Dj, he acual displacemen vecj is he difference beween DjL and he mos recen locaion of he objec corresponding o Ti. The moion affiniy is SM (Ti Dj ) = cos(veci, vecj ). () Conex Model. In modeling conex informaion, we follow he work in [22] and employ 2D hisograms of

5 T 2 T T 3 T 4 T 5 (a) Figure 6: Conex model. Conexs of (a) rajecories and (b) deecion responses are modeled by hisograms, couning objecs wihin an objec s proximiy. nearby objecs o improve he robusness. As shown in Fig. 6, here are (a) five rajecories and (b) four deecion responses. To compue a hisogram for T i, we divide he neighborhood of T i ino M pariions (here M = 4 for sake of display). For each objec locaed in his neighborhood we compue a disance vecor relaive o T i. According o he disance vecor, we accumulae he disance values for each pariion. By normalizaion, we obain an M-bin hisogram H i. The conex affiniy is S C (T i D j ) = exp( Bha(H i, H j )). (2) Having obained affiniies based on hree cues, we combine hem as follows: S(T i D j ) = S A (T i D j ) S M (T i D j ) S C (T i D j ). (3) We minimize he energy (Eq. 9) by greedy search in an ieraive way. Firs we urn off all propagaion swiches. We hen compue he affiniies of all propagaion pairs and urn on he propagaion swich (say T i and D j ) which mos decreases he energy. A he same ime, D j is labeled as he exension of T i. We remove his pair of rajecory and deecion response from he search space. This procedure is repeaed unil here is no furher energy decrease. Finally, rajecories ouside he search space are updaed considering he exended componen. The remaining rajecories in he search space are erminaed, and new rajecories are iniialized based on deecion responses in he search space. For clariy, he algorihm is summarized in Algorihm. 4. Experimens 4.. Daa ses & Seup We es our algorihm on eigh daa ses, Airshow, Goose, Sailing, Zebra, Crab, Anelope, Flower and Hockey. The firs hree are new sequences obained from YouTube videos, and he las five are public sequences [8, 20, 3]. These daa ses are challenging as hey conain () crowd This sequence is par of he original sequence in [3] (500 frames of he original 2249 frames) D 2 D 4 D (b) D 3 Algorihm : Objec label propagaion for MOT Daa: T, D, proximiy se Ω. Resul: Θ, labels of deecion responses. Iniializaion: Θ = 0. 2 while L O decrease, do 3 foreach T i T and D j Ω i, do 4 compue he energy decrease of T i and D j. 5 find T i and D j wih he greaes decrease via Eq. 9 6 se Θ ij =, propagae he label of T i o D j. 7 remove T i and D j, updae he proximiy se Ω. 8 Terminae rajecories in T, iniialize rajecories according o deecion responses in D. scenarios wih similar objecs, (2) parial or complee occlusions, (3) background cluer, and (4) ou-of-plane roaions. Parameers λ, α and η in Eq. 5 are se o be 0., 0.00 and 0.00 respecively. The proximiy parameer d T h is 20. The number of deecors is 2. For each ask, we sample 2 3 insances from he whole raining daa. We exrac HoG [9], LBP and colors as feaures for objec deecion. The hreshold o deermine he confiden insances is 0.5. Noe ha for he public daa ses, we refer o resuls repored in [8]. For daa ses which are no public, we obain resuls by running he auhors code ([3, 3]) or by re-implemening he mehod ([8] and K-SVM) Generic objec deecion We conduced experimens on generic objec deecion o verify he effeciveness of he proposed cmtl based deecion mehod. Five mehods were compared: () TLD [3] which uses a deecor based on Random Ferns; (2) K-SVM. We rain K independen SVMs on clusered raining daa from K-means clusering and deec objecs by classificaion. This is a ypical way o handle inra-class variance. The number of SVMs is four; we use he same number of clusers in our algorihm; (3) GMOT [8] is a framework which handles he same problem wih a deecor based on a Laplacian SVM; (4) our baseline mehod BL which uses cmtl wihou he spaio-emporal consisency; (5) our full mehod. Table shows he resuls. A deecion response is defined as rue posiive if is overlap wih he ground ruh bounding box is a leas 0.5. The resuls indicae ha: () TLD only discovers a small porion of objecs on some sequences. We suspec ha his is due o limiaions of he TLD deecor which uses wopixel comparisons and herefore canno handle large inraclass variance; (2) K-SVM and GMOT show good performance, and BL generally ouperforms hese, showing he effeciveness of cmtl o handle inra-class variance; (3) he full mehod ouperforms all oher mehods; in comparison wih BL he recall rae is increased due o he spaio-

6 Table : Generic objec deecion resuls in erms of recall and precision values. The bes resuls are shown in bold, he second bes are underlined. Sequence Recall TLD GMOT K-SVM BL Ours Precision TLD GMOT K-SVM BL Anelope Goose Zebra Crab Flower Airshow Sailing Hockey Avg Ours Table 2: Comparaive resuls for differen values of K (number of SVMs in K-SVM and, correspondingly, number of clusers in our mehod). Sequence Mehod Recall Precision K= Avg Avg. Anelope K-SVM Ours Zebra K-SVM Ours emporal consisency. In a separae experimen we vary he number K in K- SVM as well as he corresponding number of clusers in our algorihm. Two represenaive public sequences (Anilope and Zebra) are used in his experimen. Table 2 shows he resuls, which demonsrae ha our algorihm ouperforms K-SVM for mos K in erms of recall rae, which is imporan in our seing. Noe ha we keep K fixed for he oher experimens; a suiable choice of K is beyond he scope of his paper. In a more exensive comparison of he baseline mehod wih TLD we obain he precision-recall curves for he Anelope and Zebra sequences, shown in Fig. 7. BL uses a hreshold on he score value o deermine wheher a candidae is an objec, and TLD [3] uses he percenage of ferns voing for a posiive decision. The resuls show ha our baseline mehod ouperforms TLD consisenly. To es he variaion of performance resuling from differen iniial bounding boxes, we run our algorihm five imes on he Goose sequence, each ime labelling a differen iniial objec. The recall raes are ± and he precision raes ± 0.004, indicaing low dependence on he iniializaion (see Fig. 8). Precision Anelope BL TLD Recall Precision BL TLD Zebra Recall Figure 7: Precision-Recall performance of TLD and BL on he Anelope and Zebra sequences Recall Precision MOTA MOTP MT ML Figure 8: Performance variaion of five differen iniializaions on he Goose sequence Generic MOT We carried ou experimens o compare our framework wih several sae-of-he-ar mehods on he ask of deecing and racking muliple objecs. The experimens are presened in hree pars: () For each sequence we compare wih TLD [3] and GMOT [8]. TLD was originally developed for single objec racking, and we exended i o muliple objecs by decreasing he hreshold o le i deec some similar objecs and rack hem. I is iniialized wih he same bounding box as oher mehods. (2) For he Zebra, Crab, Flower, Airshow and Sailing sequences, we apply SPOT [3] o rack muliple objecs (four in our experimens) in each sequence. To compare he performance, we excerp resuls corresponding o hese four objecs from our whole resul in each sequence and evaluae he resuls. I is worh noing ha our algorihm sars wih

7 a single bounding box while SPOT [3] sars wih all four bounding boxes for each sequence. (3) For he Hockey sequence, we addiionally compare wih [7, 6, 20] using he resuls from [8]. Example images are shown in Fig. 9. We adop he crieria of Muliple Objec Tracking Accuracy (MOTA), Muliple Objec Tracking Precision (MOTP) proposed in [5] as well as Mosly Tracked (MT) rajecories and Mosly Loss (ML) rajecories [7] o give quaniaive resuls. MOTA akes he missed deecion, false posiives and false maches ino consideraion. MOTP measures he average overlap beween he ground ruh and he rue posiive. MT is he raio of he ground ruh rajecories which are covered by racking resuls for more han 80% in lengh. ML is he raio of he ground ruh rajecories which are covered by racking resuls for less han 20% in lengh. As shown in Table 3, he arrows following he crieria indicae he rend of beer performance. Resuls in Table 3 show ha: () compared wih TLD and GMOT, our mehod ouperforms oher mehods on mos sequences; (2) compared wih SPOT, our approach achieves beer resuls excep on he MOTP meric. We suspec ha his is due o SPOT rackers being objec-specific, hereby obaining greaer overlap scores, i.e. larger MOTP values; (3) for he Hockey sequence, our mehod obains resuls comparable wih mehods ha use a specific off-line rained human deecor. In order o es he sensiiviy on differen iniializaions, we run our algorihm on he Goose sequence five imes wih differen iniial bounding boxes. The MOTA, MOTP, MT and ML are ± 0.02, ± 0.009, ± and 0.07 ± respecively (see Fig. 8), indicaing low sensiiviy o he iniial labeling. 5. Conclusion This paper proposed a framework for racking muliple objecs of he same general ype, where class and objec labels are propagaed in he spaio-emporal domain. We inroduced cmtl for generic objec deecion and have shown he benefi of including spaio-emporal consisency. The proposed mehod akes a sequenial approach, enailing he limiaion ha objec rajecories may be more fragmened han when aking a more global view of he daa. Comparaive experimens on eigh sequences (five public and hree new daa ses) confirmed he effeciveness of he proposed mehod. From a pracical viewpoin an advanage of our mehod over mos oher work in he area is he requiremen of labeling jus a single iniial bounding box, hereby providing a muli-objec racker wihou resoring o an off-line rained deecor. Table 3: Generic Muliple Objec Tracking resuls. The able shows resuls in erms of four performance crieria from he lieraure (arrows indicaing direcion of beer performance) on five public and hree new daases. Sequence Mehod MOTA MOTP MT ML TLD [3] Anelope GMOT [8] Our mehod TLD[3] Goose GMOT [8] Our mehod TLD [3] GMOT [8] Zebra Our mehod SPOT [3] Our mehod TLD [3] GMOT [8] Crab Our mehod SPOT [3] Our mehod TLD [3] GMOT [8] Flower Our mehod SPOT [3] Our mehod TLD [3] GMOT [8] Airshow Our mehod SPOT [3] Our mehod TLD [3] GMOT [8] Sailing Our mehod SPOT [3] Our mehod TLD [3] GMOT [8] Hockey Our mehod Brendel e al. [7] Breiensein e al. [6] Okuma e al. [20] Avg. References TLD [3] GMOT [8] Our mehod SPOT [3] Our mehod [] K. Ali, D. Hasler, and F. Fleure. FlowBoos-appearance learning from sparsely annoaed video. In CVPR, 20. [2] A. Argyriou, M. Ponil, Y. Ying, and C. A. Micchelli. A specral regularizaion framework for muli-ask srucure learning. In NIPS, 2007.

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