How to cut the characters in the photo separately and not put them in the background as video material?

They are both right. Generally, PS is used for matting. One more thing: if it is a character in the video, how to dynamically cut the picture?

With the Chroma Key function with sound and shadow, you can achieve:

First, shoot a video of a character with a blue background, insert it into the audio-video superimposed track, remove the blue background with the "chroma key", and synthesize it with the background video of the video track. This is a common method of video editing today. This is how the announcer and background picture of TV weather forecast are synthesized; Many large-scale violent scenes are generally synthesized in this way. As for the blue background, it is blue that has better matting effect than other colors. Use the chroma key to remove the picture with a monochrome background, not to mention.

This method is only suitable for the matting of photos and videos with monochrome background.

Monochrome background video:

Cut the graph with chroma key, and then synthesize it later;