In this paper, we deal with the problem of temporal action localization for a large-scale untrimmed cricket videos dataset. Our action of interest for cricket videos is a cricket stroke played by a batsman, which is, usually, covered by cameras placed at the stands of the cricket ground at both ends of the cricket pitch. After applying a sequence of preprocessing steps, we have 73 million frames for 1110 videos in the dataset at constant frame rate and resolution. The method of localization is a generalized one which applies a trained random forest model for CUTs detection(using summed up grayscale histogram difference features) and two linear SVM camera models(CAM1 and CAM2) for first frame detection, trained on HOG features of CAM1 and CAM2 video shots. CAM1 and CAM2 are assumed to be part of the cricket stroke. At the predicted boundary positions, the HOG features of the first frames are computed and a simple algorithm was used to combine the positively predicted camera shots. In order to make the process as generic as possible, we did not consider any domain specific knowledge, such as tracking or specific shape and motion features. The detailed analysis of our methodology is provided along with the metrics used for evaluation of individual models, and the final predicted segments. We achieved a weighted mean TIoU of 0.5097 over a small sample of the test set.
Some of the above approaches need pre-trained models that can be fine-tuned on their own problem specific datasets, while some other use large benchmark datasets for training purpose. Applying such techniques for a sporting event requires a lot of hand-annotated training data, which is hard to get or may include a lot of noise. Automated ways of creating datasets may involve using a third party API, like YouTube Data API (as done in @cite_35 ), or extraction using text meta-data of videos, which may not, at all, be accurate. @cite_31 proposed a method to extract action videos based on the tags. Deciding the relevancy of a tag, in itself, is a research problem. Due to these reasons, content-based action extraction from videos is a good choice for automatic construction of large-scale action dataset. @cite_15 provide a survey of the content-based methods for video extraction.
@cite_35 @cite_31 @cite_15
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Convolutional Neural Networks (CNNs) have been established as a powerful class of models for image recognition problems. Encouraged by these results, we provide an extensive empirical evaluation of CNNs on large-scale video classification using a new dataset of 1 million YouTube videos belonging to 487 classes. We study multiple approaches for extending the connectivity of a CNN in time domain to take advantage of local spatio-temporal information and suggest a multiresolution, foveated architecture as a promising way of speeding up the training. Our best spatio-temporal networks display significant performance improvements compared to strong feature-based baselines (55.3 to 63.9 ), but only a surprisingly modest improvement compared to single-frame models (59.3 to 60.9 ). We further study the generalization performance of our best model by retraining the top layers on the UCF-101 Action Recognition dataset and observe significant performance improvements compared to the UCF-101 baseline model (63.3 up from 43.9 ). Video sharing websites have recently become a tremendous video source, which is easily accessible without any costs. This has encouraged researchers in the action recognition field to construct action database exploiting Web sources. However Web sources are generally too noisy to be used directly as a recognition database. Thus building action database from Web sources has required extensive human efforts on manual selection of video parts related to specified actions. In this paper, we introduce a novel method to automatically extract video shots related to given action keywords from Web videos according to their metadata and visual features. First, we select relevant videos among tagged Web videos based on the relevance between their tags and the given keyword. After segmenting selected videos into shots, we rank these shots exploiting their visual features in order to obtain shots of interest as top ranked shots. Especially, we propose to adopt Web images and human pose matching method in shot ranking step and show that this application helps to boost more relevant shots to the top. This unsupervised method of ours only requires the provision of action keywords such as ''surf wave'' or ''bake bread'' at the beginn ing. We have made large-scale experiments on various kinds of human actions as well as non-human actions and obtained promising results.