Re: It doesn't matter how good the display is if there's nothing to display
The BBC some time ago (at least) transmitted BBC 1 HD with an output that swapped between interlaced and progressive at the GOP boundaries depending on which they were getting a better compression from.
This has now been rolled out to all services on the PSB3 Freeview HD multiplex (BBC One/Two/Three HD, ITV HD, 4hd) and I believe it is also used on COM7 (CBeebies/BBC Four, Channel 4+1, 4seven, Al Jazeera HD).
I don't think it is used on satellite - changing the interlacing mode on a GOP basis was not part of the Freesat or Sky specifications. Doing this caused a problem on early Freeview HD units, and in some cases TVs using external Freeview HD boxes (it depended whether the box passes through the 1080p25 GOPs or converts to 1080i50). There tended to be brief switches to black and audio glitches on mode switches - annoying but bearable on programme transitions, not acceptable when it could switch more than once per second (a GOP is usually shorter than 25 frames)
Biting the hand that feeds IT
