In Lightroom 4.1 (Windows 7 64 bit) when I create a slideshow in the Slideshow Module, use Export Video 720p or 1080p, the properties of the export do not agree with the name of the preset suggesting a fundamental discrepancy in what is stated and what is.
The MediaInfo properties readout for this type of export is showing Scan Type = Interlaced and Scan Order = Top Field First. How is this possible for 720p and 1080p which are designations for progressive video (no Fields)? However, the readout will show the expected frame rates, 1280 x 720 or 1920 x 1080 for 720p and 1080p respectively.
I suspect that this is not a misread by MediaInfo since a Mac user shows the same "interlaced" & "upper field first" information using a Mac Video Specs application for the properties readout for the Slideshow Module Export Video 1080p.