This is something not so easy to find on the internet, and once again Linux shows its immense power in the simplest way: CLI.
Question: I have a .ISO file representing the image of a DVD and I want to know the LABEL of that DVD.
Answer: Issue the command
dd if=/<path>/filename.iso bs=1 skip=32808 count=32
on whatever Linux terminal.
For example, here’s what is returned for a backup copy of DVD I legally own:
dd if=Natale\ in\ Casa\ Muppets.iso bs=1 skip=32808 count=32
MUPPETS_CHRISTMAS_CAROL 32+0 records in
32+0 records out
32 bytes (32 B) copied, 0.00129793 s, 24.7 kB/s