NTU60 frame names

[MABatin]

Hi,
in skeleton-based action recognition format for ntu60 dataset, 'frame_dir' key contains the name of the video clip of a label. An example of the name of a clip is "S011C001P019R001A023". My question is what does the S, C, P and R values correspond to? I know that the label is included after the A value, e.g. in this case the label is 22.

Thanks in advance.