There are various tools and commands to find duplicate files (i.e. find command), but those usually find exact matches which does not help with media files (music,video,images) that have been resized,reencoded,contain watermarks, etc). The following tools help find those duplicates.

Video Duplicate Finder (Win/Linux) finds Videos and Images based on similarity:

https://github.com/0x90d/videoduplicatefinder/releases

wget "https://github.com/0x90d/videoduplicatefinder/releases/download/2.0.7/VDF.Linux-x64.tar.gz"
tar -xvzf VDF.Linux-x64.tar.gz
rm VDF.Linux-x64.tar.gz
cd VDF.Linux-x64
./VideoDuplicateFinderLinux

Dupeguru (Win/Linux/Mac) finds Music, Images and general files:

https://dupeguru.voltaicideas.net/

sudo apt-add-repository ppa:dupeguru/ppa
sudo apt-get update

#The apps are:
dupeguru-se = standard edition
dupeguru-me = music edition
dupeguru-pe = picture edition

FSlint is a find frontend and finds exact matches, temp files, bad symlinks etc on linux

sudo apt-get install fslint