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Estimating 3D poses from a monocular video is still a challenging task, despite the significant progress that has been made in the recent years. Generally, the performance of existing methods drops when the target person is too small/large, or the motion is too fast/slow relative to the scale and speed of the training data. Moreover, to our knowledge, many of these methods are not designed or trained under severe occlusion explicitly, making their performance on handling occlusion compromised. Addressing these problems, we introduce a spatio-temporal network for robust 3D human pose estimation. As humans in videos may appear in different scales and have various motion speeds, we apply multi-scale spatial features for 2D joints or keypoints prediction in each individual frame, and multi-stride temporal convolutional networks (TCNs) to estimate 3D joints or keypoints. Furthermore, we design a spatio-temporal discriminator based on body structures as well as limb motions to assess whether the predicted pose forms a valid pose and a valid movement. During training, we explicitly mask out some keypoints to simulate various occlusion cases, from minor to severe occlusion, so that our network can learn better and becomes robust to various degrees of occlusion. As there are limited 3D ground truth data, we further utilize 2D video data to inject a semi-supervised learning capability to our network. Experiments on public data sets validate the effectiveness of our method, and our ablation studies show the strengths of our network's individual submodules.

Automatic player detection, labeling and tracking in broadcast soccer video are significant while quite challenging tasks. In this paper, we present a solution to perform automatic multiple player detection, unsupervised labeling and efficient tracking. Players' position and scale are determined by a boosting based detector. Players' appearance models are unsupervised learned from hundreds of samples automatically collected by detection. Thereafter, these models can be utilized for player labeling (Team A, Team B and Referee). Player tracking is achieved by Markov Chain Monte Carlo (MCMC) data association. Some data driven dynamics are proposed to improve the Markov chain's efficiency. The testing results on FIFA World Cup 2006 video demonstrate that our method can reach high detection and labeling precision, and reliably tracking in cases of scenes such as multiple player occlusion, moderate camera motion and pose variation. IntroductionAutomatic player localization, labeling and tracking is critical for team tactics, player activity analysis and enjoyment in broadcast sports videos. It is quite challenging due to many difficulties such as player-to-player occlusion, similar player appearance, varying number of players, abrupt camera motion, various noises, video blur, etc.Many algorithms have been presented to deal with the multiple target tracking problem, such as particle filter [1 of these two works, a multi-camera system was used to get a stationary, high-resolution and wide-field view of soccer game. This setting ensured a reliable background subtraction can be obtained. In our application, the camera is not fixed, which results in moving background. Thus, we need robust and adaptive background modeling and effective object association technologies. In another aspect, unsupervised player labeling is preferred for its generalization ability. In this paper, we propose a solution for player detection, labeling and tracking in broadcast soccer video. The system framework is illustrated in Figure 1. The whole procedure is a two-pass video scan. In the first scan, we (1) learn video dominant color via accumulated color histograms, and (2) unsupervised learn players' appearance models over hundreds of player samples collected by a boosted player detector. In the second scan, that is the testing procedure, we first use the dominant color for playfield segmentation and view-type classification. Then we apply a boosting player detector to localize players. Afterwards, the players are labeled as Team A, Team B or Referee with prior learned models. Finally, we perform data-driven MCMC association to generate players' trajectories, in which track length, label consistency and motion consistency are used as criterions for associating observations across frames.The main contributions of our method are: (1) robust player detection achieved by background filtering and a boosted cascade detector; (2) unsupervised player appearance modeling, the referee can be identified in addition to two teams players without any ...

Although gait recognition has drawn increasing research attention recently, it remains challenging to learn discriminative temporal representation, since the silhouette differences are quite subtle in spatial domain. Inspired by the observation that human can distinguish gaits of different subjects by adaptively focusing on temporal clips with different time scales, we propose a context-sensitive temporal feature learning (CSTL) network for gait recognition. CSTL produces temporal features in three scales, and adaptively aggregates them according to the contextual information from local and global perspectives. Specifically, CSTL contains an adaptive temporal aggregation module that subsequently performs local relation modeling and global relation modeling to fuse the multi-scale features. Besides, in order to remedy the spatial feature corruption caused by temporal operations, CSTL incorporates a salient spatial feature learning (SSFL) module to select groups of discriminative spatial features. Particularly, we utilize transformers to implement the global relation modeling and the SSFL module. To the best of our knowledge, this is the first work that adopts transformer in gait recognition. Extensive experiments conducted on three datasets demonstrate the state-of-the-art performance. Concretely, we achieve rank-1 accuracies of 98.7%, 96.2% and 88.7% under normal-walking, bag-carrying and coat-wearing conditions on CASIA-B, 97.5% on OU-MVLP and 50.6% on GREW.

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