No video after rendering

[LunaBright]

hello, May I ask why there are only images but no videos after rendering with render_video.py file? As shown in the figure below:

[LunaBright]

And there are black part of the top of every image after rendering, like this. I am confused why is this occured:

[LunaBright]

I understand the problem I had earlier. But I would like to ask if I want to render a video, do I need to assemble the rendered images into a video? Is there a way to output the video directly?