I figured out this question by discussing with co-working engineers and reading the HLS document: https://datatracker.ietf.org/doc/html/rfc8216#section-4.3.2.6 It seems that there's a m3u8 tag EXT-X-PLAYLIST, which defines whether the content is LIVE. If this tag has a specific event value doesn't have a value, it's defined LIVE.

Thank you. I get it. Is it possible to hide or customize the appearance of the LIVE badge? I try to find live-related property of AVPlayerViewController, but it seems there's no relevant one.