详见3D Skeleton-based Human Action Classification: a Survey

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数据预处理:

In 3D skeleton-based action classification, an action is described as a collection of time series of 3D positions (i.e., 3D trajectories) of the joints in the skeleton.

同一动作的关节3D坐标可能会出现较大差异

1.subject所处的位置距离kinect不同
2.subject具有个体差异性，也是intraclass variation
解决方法：

1. 可以选取关节角度作为特征，角度不会受限于个体差异性
2. human poses are normalized by aligning torsos and shoulders
3. all of the 3D joint coordinates are transformed from world coordinate system to person centric coordinate system by placing the Hip Center (以胯部为中心)
4. 以头部为中心进行归一化
5. 所有坐标归一化到[0,1]

论文翻译

HOJ3D

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解决序列长短问题

globalfeatures 将所有同一类的所有样本提取特征，如KMEANS BOW VLAD