Face Recognition from Weakly Labeled Data
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Recognizing the identity of a face or a person in the media usually requires lots of training data to design robust classifiers, which demands a great amount of human effort for annotation. Alternatively, the weakly labeled data is publicly available, but the labels can be ambiguous or noisy. For instance, names in the caption of a news photo provide possible candidates for faces appearing in the image. Names in the screenplays are only weakly associated with faces in the videos. Since weakly labeled data is not explicitly labeled by humans, robust learning methods that use weakly labeled data should suppress the impact of noisy instances or automatically resolve the ambiguities in noisy labels. We propose a method for character identification in a TV-series. The proposed method uses automatically extracted labels by associating the faces with names in the transcripts. Such weakly labeled data often has erroneous labels resulting from errors in detecting a face and synchronization. Our approach achieves robustness to noisy labeling by utilizing several features. We construct track nodes from face and person tracks and utilize information from facial and clothing appearances. We discover the video structure for effective inference by constructing a minimum-distance spanning tree (MST) from the track nodes. Hence, track nodes of similar appearance become adjacent to each other and are likely to have the same identity. The non-local cost aggregation step thus serves as a noise suppression step to reliably recognize the identity of the characters in the video. Another type of weakly labeled data results from labeling ambiguities. In other words, a training sample can have more than one label, and typically one of the labels is the true label. For instance, a news photo is usually accompanied by the captions, and the names provided in the captions can be used as the candidate labels for the faces appearing in the photo. Learning an effective subject classifier from the ambiguously labeled data is called ambiguously labeled learning. We propose a matrix completion framework for predicting the actual labels from the ambiguously labeled instances, and a standard supervised classifier that subsequently learns from the disambiguated labels to classify new data. We generalize this matrix completion framework to handle the issue of labeling imbalance that avoids domination by dominant labels. Besides, an iterative candidate elimination step is integrated with the proposed approach to improve the ambiguity resolution. Recently, video-based face recognition techniques have received significant attention since faces in a video provide diverse exemplars for constructing a robust representation of the target (i.e., subject of interest). Nevertheless, the target face in the video is usually annotated with minimum human effort (i.e., a single bounding box in a video frame). Although face tracking techniques can be utilized to associate faces in a single video shot, it is ineffective for associating faces across multiple video shots. To fully utilize faces of a target in multiples-shot videos, we propose a target face association (TFA) method to obtain a set of images of the target face, and these associated images are then utilized to construct a robust representation of the target for improving the performance of video-based face recognition task. One of the most important applications of video-based face recognition is outdoor video surveillance using a camera network. Face recognition in outdoor environment is a challenging task due to illumination changes, pose variations, and occlusions. We present the taxonomy of camera networks and discuss several techniques for continuous tracking of faces acquired by an outdoor camera network as well as a face matching algorithm. Finally, we demonstrate the real-time video surveillance system using pan-tilt-zoom (PTZ) cameras to perform pedestrian tracking, localization, face detection, and face recognition.