This is a misconception. Images and videos "on Nostr" are simply uploaded to normal HTTP servers, and native Nostr notes only contain links to them.
What a client does or does not render inline (so it looks like it's part of the Nostr note) depends entirely on the client.
Don’t know about your client, but on #damus, images are uploaded to an ordinary HTTP server and linked into the note, not inlined.
Advantage: simple
Disadvantage: very centralized and not very censorship resistant
That was my point. A livestream would work the same way, and it's just a matter of the client rendering it inline or not.
By the way, this is usually done via oEmbed around the rest of the Web: https://oembed.com
