DVD video playing quality not clear

Hi, recently got a dvd player from a friend. It works fine, but somehow it still has slight wavey lines with i play the video. I tried messing the all the settings still doesn’t improve. It is definitely watchable, but I’d like the lines to go away. Any ideas?

Better cables?

Use RGB cables instead of s-video connection

What connection / cables do you use between the DVD player and the TV? And I take it the DVDs are original, or rather of good quality?