In this paper, we propose a novel multi-class graph boosting algorithm to recognize different visual objects. The proposed method treats subgraph as feature to construct base classifier, and utilizes popular error correcting output code scheme to solve multi-class problem. Both factors, base classifier and error-correcting coding matrix are considered simultaneously. And subgragphs, which are shareable by different classes, are wisely used to improve the classification performance. The experimental results on multi-class object recognition show the effectiveness of the proposed algorithm.

Human action recognition is a significant task in automatic understanding systems for video surveillance. Probabilistic Latent Semantic Analysis (PLSA) model has been used to learn and recognize human actions in videos. Specifically, PLSA employs the expectation maximization (EM) algorithm for parameter estimation during the training. The EM algorithm is an iterative estimation scheme that is guaranteed to find a local maximum of the likelihood function. However its convergence usually takes a large number of iterations. For action recognition with large amount of training data, this would result in long training time. This paper presents an incremental version of EM to speed up the training of PLSA without sacrificing performance accuracy. The proposed algorithm is tested on two challenging human action datasets. Experimental results demonstrate that the proposed algorithm converges with fewer number of full passes compared with the batch EM algorithm. And the trained PLSA models achieve comparable or better recognition accuracies than those using batch EM training.

A multiclass classification problem can be reduced to a collection of binary problems using an error-correcting coding matrix that specifies the binary partitions of the classes. The final classifier is an ensemble of base classifiers learned on binary problems and its performance is affected by two major factors: the qualities of the base classifiers and the coding matrix. Previous studies either focus on one of these factors or consider two factors separately. In this paper, we propose a new multiclass boosting algorithm called AdaBoost.SIP that considers both two factors simultaneously. In this algorithm, informative patterns, which are shareable by different classes rather than only discriminative on specific single class, are generated at first. Then the binary partition preferred by each pattern is found by performing stage-wise functional gradient descent on a margin-based cost function. Finally, base classifiers and coding matrix are optimized simultaneously by maximizing the negative gradient of such cost function. The proposed algorithm is applied to scene and event recognition and experimental results show its effectiveness in multiclass classification.

In this paper, we propose a novel approach to automatically generating, instead of manually designing, discriminative visual features for face detection. The features are composed by multiple local features (e.g., Haar features), and such features can capture not only the local texture information but also their spatial configurations. Therefore, the proposed feature contains rich semantic information so that the classifier built on a set of such features can achieve high accuracy and high efficiency. Experimental results show that the proposed approach outperforms the techniques based on local features and the state-of-the-art discriminative features for face detection.

Multi-instance learning (MIL) has many applications, including image and text categorization. One of the most effective approaches to MIL is by using support vector machines with multi-instance kernels. In this paper we propose a multi-instance kernel, called MIR-kernel, that takes into account the relational information of instances when computing similarities between bags. The relational information of instances are derived from the statistics of the distances between instances in feature space. The aim of MIR-kernel is to efficiently capture the context in which instances occur within bags, so that it is able to better compute the similarities between bags. Experimental results on image and text categorization demonstrate the effectiveness of the proposed method compared to other methods.

In this paper, we propose an efficient approach to moving pedestrian detection in video. This approach incorporates both motion and shape information and learns a codebook of shape context descriptors from a very small number of training samples. During the testing process, moving edgelets are firstly identified between adjacent frames using a local search method. Shape context descriptors for numerous sample points on identified edgelets are then produced and are matched against the instances of the learned codebook to generate initial hypotheses. The final hypotheses for pedestrians are obtained by pruning initial hypotheses. The proposed approach has the following advantages by comparison with the existing techniques: (1) lower computational cost, (2) lower false positive rate, and (3) fewer training samples. Experiments with a publicly available dataset confirm the performance of the proposed approach.

In this paper we propose a new algorithm for region-based image categorization that is formulated as a multiple instance learning (MIL) problem. The proposed algorithm transforms the MIL problem into a traditional supervised learning problem, and solves it using a standard supervised learning method. The features used in the proposed algorithm are the hyperclique patterns which are ldquocondensedrdquo into a small set of discriminative features. Each hyperclique pattern consists of multiple strongly-correlated instances (i.e., features). As a result, hyperclique patterns are able to capture the information that are not shared by individual features. The advantages of the proposed algorithm over existing algorithms are threefold: (i) unlike some existing algorithms which use learning methods that are specifically designed for MIL or for certain datasets, the proposed algorithm uses a general-purpose standard supervised learning method, (ii) it uses a significantly small set of features which are empirically more discriminative than the PCA features (i.e. principal components), and (iii) it is simple and efficient and achieves a comparable performance to most state-of-the-art algorithms. The efficiency and good performance of the proposed algorithm make it a practical solution to general MIL problems. In this paper, we apply the proposed algorithm to both drug activity prediction and image categorization, and promising results are obtained.

Detecting and recognizing pedestrians in video footages are two essential and significant tasks in many automatic video understanding systems. In this paper, we propose an efficient approach to moving pedestrian detection and recognition in video. The testing process of this approach involves two main steps: moving edge detection and hypotheses generation. Moving edges are firstly extracted by comparing the edges identified in adjacent frames. Shape context descriptors are then produced for the edge points sampled from the moving edges and matched against the instances of a codebook that is learned from a set of training samples to generate initial hypotheses. Final hypotheses are formed by pruning initial hypotheses with large overlaps. Experiments with a publicly available dataset show that the proposed approach can reliably detect and recognize moving pedestrians in real scenes that contain either different viewing angles or different degrees of occlusions.

The MPEG-4 video coding standard introduces a novel concept of sprite or mosaic that is a large image composed of pixels belonging to a video object visible throughout a video segment. The sprite captures spatio-temporal information in a very compact way and makes it possible for efficient object-based video compression. In this paper, we propose a practical approach to generating multiple super-resolution sprites for sprite coding. In order to construct super-resolution sprites and reduce coding cost, we firstly partition a video sequence into multiple independent sprites and group the images covering a similar scene into the same sprite. We then propose efficient and practical algorithms for cumulative global motion estimation and super-resolution sprite construction. Experiments with real video sequences show that the proposed approach outperforms the previous single sprite and multiple sprite techniques.

In this paper, the performance of the Earth Mover's Distance (EMD) vs /spl chi//sup 2/ distance as histogram similarity metrics for image retrieval is evaluated experimentally. Ground truth is generated in two ways: through a novel approach of extracting frames from video shots and through random sampling. Quantitative evaluations of the retrieval performance with regular partitioning, clustered and adaptive binning histograms and with various number of bins are given. Meanwhile the influence of ground distance functions to the performance of the EMD is also studied. The findings of the paper may constitute guidelines in adopting the EMD.