If you need to find duplicate films/music files on a large hard drive quickly there is a version of fdupes which does this job in seconds.
fdupe -cr will find the duplicates and fdupe -crd will allow you to choose which duplicate to keep.
When you are done choosing you can press delete to delete all the files not marked to keep or you can type prune to do the same.
To compile and install use these instructions on your RPi
apt install build-essential git libpcre2-dev pkg-config make automake autoconf libncurses-dev
git clone https://github.com/Arseney300/fdupes.git
git checkout large_files
autoreconf --install
autoconf
./configutre
make
make install
fdupes -crd /mnt/your-disk-drive/your-films
example:
fdupes -crd /mnt/5d3564f4-dbc6-414f-8cf2-3a4352ed7133/films
explicit; note that duplicate detection is based only on file size when using -c and the files are never really fully compared.