def extract_frame(frame_info):
    self.fp.seek(frame_info.loc)
    record = self.fp.read(frame_info.length)
    img_str = record[:(len(record) - frame_info.pad)]
    img = self.jpeg_decoder(img_str)
    return img
def extract_frame(frame_info):
    self.fp.seek(frame_info.loc)
    record = self.fp.read(frame_info.length)
    img_str = record[:(len(record) - frame_info.pad)]
    img = self.jpeg_decoder(img_str)
    return img