Hmm. I'm still trying to grasp this, here. So what they simply mean by 60p is that it really is 30 true progressive frames but will be sent out as 60 "segments" so it can be read by 1080i, and that this isn't truly 60 progressive frames?
As you said, it can be re-assembled to make a complete frame, which would end up to be 30 frames. Now how does that differ from 60i? Is it just that the recording process truly does record in progressive instead of interlace right off the bat? Oh, and also when it's re-assembled, is it compatible with 1080p as well as 1080i?
Right, 60 progressive frames is twice as much data as 30p or 60i. It's a stretch to do 60p in high end pro gear, let alone consumer stuff. So, they're definitely not talking about real 60p. They mean 30p, but recorded as if it were 60i. Yet another reason why this is dumb and disgusting.
The big differences between true 60i and 30p recorded in the 60 "segments" that work sort of like fields method are:
1. The segments that make up a progressive frame are both from the same time sample. Moving objects are in the same position in both segments. Interlaced fields represent two different times, 1/60 second apart. Moving objects are in different places in the two fields of interlaced TV, so if you try to just put them together, their edges get "mouse teeth".
2. The image content of 60i has to be low pass filtered to a lower resolution than 30p, because the Nyquist limit for 60i is lower. To do it absolutely right, you'd have to cut the i resolution to exactly half of the p resolution. But, funny thing, people accept a little bit of interline flicker, which means that you can get away with more like 65% instead of just 50%. That's the whole reason for interlace in the first place. That's a kind of lossy compression that works in analog, so it was a useful way to get sharper pictures back in the 1930's when this stuff was developed. Interlace was the right answer for half a century. Now that we have digital compression, it does more harm than good. We can do better compression with less loss, interlace just interferes with that.