Automaticly download and update youtube playlist

I am using youtube-dl to download my music playlist.

Theres only one problem: youtube-dl doesn't realize which videos it has already downloaded, so it simply redownloads every single video. I would like it to recongize when new videos have been added and then only redownload those, so that I could run it every 10 seconds or so to check whether or not new videos have been added.

Alternatively I would like a way to download all urls present in a yt playlist, so I can download it and check it against the already downloaded ones, so I can simply runt yt download on those instead.

Basicly I would like a way to get an up to date local copy on my pc of my yt playlist.