def get_data_file_path_list(data_file_list_path):
    """Get mappting of video id to sensor data files.

    video id to (original video id, [file 1, ..., file n])
     where file 1, ..., file n are one series data.
    Note.
    - Original video id in input files sometimes mixed lower and upper case.
    - To treat several case, lower case of them are used as key of mapping.
    """
    mapping = {}
    with open(data_file_list_path) as f_in:
        for line in f_in.readlines():
            if line.strip() == '':
                continue
            video_name_prefix, files_txt = line.strip().split('\t')
            mapping[video_name_prefix.lower()] = (
                video_name_prefix, files_txt.split(','))
    return mapping