[keithwinstein]

Not so -- 1080p24 and 1080p30 sequences (and the 1000/1001-rate versions) were part of the original A/53 specification in 1995. This is for H.262 video (MPEG-2 part 2). It's also in the 2007 revision (see A/53:2007 part 4, table 6.1.2 [1]). In practice, what broadcasters really do is send a sequence labeled 1080i30 for everything, but during the 24P content, they send 24 progressive-scan frame pictures per second, with picture flags that instruct the decoder how to perform the 3:2 pulldown to manufacture 60 fields per second at the receiver. This kind of "1080p24" is very common and they've been doing it since the 90s or early 2000s. The same basic technique is used on NTSC DVDs.

([1] https://prdatsc.wpenginepowered.com/wp-content/uploads/2021/.... Pedantic note: What the FCC adopted is slightly more generous than the ATSC spec; they excluded this table, both pre- and post-2007. So technically speaking, anything "Main Profile @ High Level" is allowed on the U.S. airwaves, but it doesn't matter in practice.)