CASIA-B
    001 (subject)
        bg-01 (type)
            000 (view)
                001-bg-01-000-001.png (frame)
                001-bg-01-000-002.png (frame)
                ......
            ......
        ......
    ......

Run python misc/pretreatment.py --input_path CASIA-B --output_path CASIA-B-pkl

Processed

CASIA-B-pkl
    001 (subject)
        bg-01 (type)
                000 (view)
                    000.pkl (contains all frames)
            ......
        ......
    ......