wan2.2 如果要训练首尾帧，是不是需要把训练数据变换到81帧以内，不然就被截断了

class LoadVideo(DataProcessingOperator, FrameSamplerByRateMixin):
def init(self, num_frames=81, time_division_factor=4, time_division_remainder=1, frame_processor=lambda x: x, frame_rate=24, fix_frame_rate=False):
FrameSamplerByRateMixin.init(self, num_frames, time_division_factor, time_division_remainder, frame_rate, fix_frame_rate)
# frame_processor is build in the video loader for high efficiency.
self.frame_processor = frame_processor

def __call__(self, data: str):
    reader = self.get_reader(data)
    raw_frame_rate = reader.get_meta_data()['fps']
    num_frames = self.get_num_frames(reader)
    total_raw_frames = reader.count_frames()
    frames = []
    for frame_id in range(num_frames):
        frame_id = self.map_single_frame_id(frame_id, raw_frame_rate, total_raw_frames)
        frame = reader.get_data(frame_id)
        frame = Image.fromarray(frame)
        frame = self.frame_processor(frame)
        frames.append(frame)
    reader.close()
    return frames

Start with LoadVideo and trace FrameSamplerByRateMixin, especially get_num_frames and map_single_frame_id. Verify how videos longer than 81 frames are sampled and whether first/last-frame training data is truncated; done means documenting the behavior or defining the required handling for those inputs.