[mythtvnz] Difference between Advanced 1x and 2x De-interlacers?

[Tortise]

I've been looking to find information that explains the difference between 1x and 2x advanced - and what they actually do.

Some introductory links:

http://www.mythtv.org/wiki/Deinterlacing
http://en.wikipedia.org/wiki/Interlace

These are useful:

http://www.100fps.com/
http://guru.multimedia.cx/deinterlacing-filters/

This is directly related to our situation

http://http.download.nvidia.com/XFree86/vdpau/doxygen/html/index.html

This one details how advanced is the only method to utilise the data in the preceding and following fields (two fields that together 
comprise a frame), however it does not define what 1x nor 2x actually does.  It also suggests some "p" content can also be enhanced.

It seems to me that 1x possibly turns each field into a frame effectively converting an interlaced stream into progressive display 
and that 2x possibly puts a calculated frame in between each original field to double the rate.  Can anyone advance this from 
speculation to fact.

Also related is out broadcast frame rates as best I can tell here in NZ, it seems our 576i is 50 fields/sec to make 25 frames per 
second.  Perhaps our 720p and 1080i are at the equivalent rates?

I am interested in this as some TV's now feature 100 (and even 200) fps displays that also seem to calculate in between frames to 
effectively increase frame rates while not only preserving but also enhancing movement. They will presumably add intermediate frames 
in for both "i" and "p" streams.  Would they add to, subtract from, or make no difference to HD in mythtv?

It therefore seems that a 100 fps TV may well enhance a 50 fps ?1x or 2x "advanced output" from mythtv however if 2x is 100fps there 
may be little to gain?  One limiting factor here will be the max input fps capacity of the monitor.  That is a 100fps monitor may 
only take in 50 fps and process it to 100 or alternatively it might also receive and display 100fps.

In advance many thanks to anyone who can progress this summary.