Originally Posted by BrianO
The overall bandwidth restriction eliminates 1080p at 60 frames per second from the ATSC standard but 1080p at 24 fps and 30 fps are valid ATSC OTA broadcast formats that have been part of the standard since Day 1. Disregarding the fact that progrssive scan has been found to be a little easier to compress using MPEG-2, 1080p/30 requires the same bandwidth that 1080i requires and 1080p/24 takes less bandwidth than 720p/60. The oft quoted factoid that 1080p requires too much bandwidth for OTA broadcasting is nothing more than a myth that won't die, propagated by people who do not understand that progressive scan involves multiple frame rates.
You have a point here, but there are several practical issues concerning the different variants of 1080p that need to be kept in mind. 1080p/24 especially, and 1080p/30 to a lesser degree, have readily perceived flicker on a number of displays; more to the point, these aren't formats used by any broadcast networks or syndicators, and much of our HD studio equipment does not even support these frame rates. Are they valid under the ATSC standard? Sure... but as a practial matter they are irrelevant to over-the-air broadcasters.
On the other hand, 1080p/60 represents a qualitative improvement over both 720p and 1080i as generally implemented, and is the frame rate most people infer when you talk about 1080p.
To say that we can't encode 1080p into an ATSC system isn't so much a myth as a shorthand that addresses the only variant someone would likely want
to encode, and ignores the others.