论文标题

时间序列和序列的不确定性-DTW

Uncertainty-DTW for Time Series and Sequences

论文作者

Wang, Lei, Koniusz, Piotr

论文摘要

动态时间扭曲(DTW)用于匹配序列对,并在应用程序中庆祝,例如预测时间序列的演变,聚类时间序列或偶数匹配的序列对,以几次拍摄的动作识别。 DTW的运输计划包含一组路径;每条路径在不同程度的扭曲程度下与两个序列之间的帧匹配,以说明各种阶段的动作动力。但是,由于DTW是所有路径之间最小的距离,因此它可能会受到特征不确定性的影响,该功能不确定性随时间步长/帧而变化。因此,在本文中,我们建议对DTW的可区分(软)版本的所谓质地不确定性进行建模。为此,我们通过正常分布的可能性乘积(每个捕获一对框架的差异)对每种路径的异质分裂不确定性进行建模。 (路径距离是路径框架对的特征之间的基本距离的总和。)应用于路径的最大似然估计(MLE)产生两个术语:(i)由方差逆加权加权的欧几里得距离之和(ii)对数差异的差异符合条件的总和。因此,我们的不确定性-DTW是所有路径之间最小的加权路径距离,而正则化项(高不确定性的惩罚)是沿路径的对数变化的汇总。距离和正则项可以用于各种目标。我们展示了预测时间序列的演变,估计了时间序列的平均值,并监督/无监督的几乎没有射击的动作识别对铰接的人类3D身体关节的识别。

Dynamic Time Warping (DTW) is used for matching pairs of sequences and celebrated in applications such as forecasting the evolution of time series, clustering time series or even matching sequence pairs in few-shot action recognition. The transportation plan of DTW contains a set of paths; each path matches frames between two sequences under a varying degree of time warping, to account for varying temporal intra-class dynamics of actions. However, as DTW is the smallest distance among all paths, it may be affected by the feature uncertainty which varies across time steps/frames. Thus, in this paper, we propose to model the so-called aleatoric uncertainty of a differentiable (soft) version of DTW. To this end, we model the heteroscedastic aleatoric uncertainty of each path by the product of likelihoods from Normal distributions, each capturing variance of pair of frames. (The path distance is the sum of base distances between features of pairs of frames of the path.) The Maximum Likelihood Estimation (MLE) applied to a path yields two terms: (i) a sum of Euclidean distances weighted by the variance inverse, and (ii) a sum of log-variance regularization terms. Thus, our uncertainty-DTW is the smallest weighted path distance among all paths, and the regularization term (penalty for the high uncertainty) is the aggregate of log-variances along the path. The distance and the regularization term can be used in various objectives. We showcase forecasting the evolution of time series, estimating the Fréchet mean of time series, and supervised/unsupervised few-shot action recognition of the articulated human 3D body joints.

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