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Leveraging intra-class variations to improve large vocabulary gesture recognition

Large vocabulary gesture recognition using a training set of limited size is a challenging problem in computer vision. With few examples per gesture class, researchers often employ exemplar-based methods such as Dynamic Time Warping (DTW). This paper makes two contributions in the area of exemplar-based gesture recognition: 1) it introduces Multiple-Pass DTW (MP-DTW), a method in which scores from multiple DTW passes focusing on different gesture properties are combined, and 2) it introduces a new set of features modeling intra-class variation of several gesture properties that can be used in conjunction with MP-DTW or DTW. We demonstrate that these techniques provide substantial improvement over DTW in both user-dependent and user-independent experiments on American Sign Language (ASL) datasets, even when using noisy data generated by RGB-D skeleton detectors. We further show that using these techniques in a large vocabulary system with a limited training set provides significantly better results compared to Long Short-Term Memory (LSTM) network and Hidden Markov Model (HMM) approaches.