Trying to understand the working with fields

[audiohominis]

Hi, guys.
I have a 29.97fps progressive video with a pixel resolution of 1920x1088 and 16:9DAR (effectively 1920x1080p). What I need to do is convert it to a 1440x1088 29.97fps interlaced video whilst maintaining the 16:9 DAR (effectively 1920x1080i).
The docs gave me some king of an idea of the commands for working with fields but I just don't know how to go about it. I use MeGUI. Since the source already is 29.97fps I don't suppose I have to use pull down. (I'm confused aren't I).
Thanks

[Alex_ander]

It is only possible to produce interlaced from progressive in case the source has double framerate. That's because in a true interlaced video each field belongs to its own moment in time and you want to produce twice as many fields. In case of 29.97 progressive you can only produce a fake interlaced video by field shifting between frames (not much useful) or to try frame interpolation with mvtools2' MFlowFPS function (possible, but not always perfect) for getting double framerate, then combine fields.

[nm]

Hi, guys.
I have a 29.97fps progressive video with a pixel resolution of 1920x1088 and 16:9DAR (effectively 1920x1080p). What I need to do is convert it to a 1440x1088 29.97fps interlaced video whilst maintaining the 16:9 DAR (effectively 1920x1080i).

I doubt you really need interlaced video. Resize to 1440x1088 and encode it "as interlaced" (2:2 pulldown, doesn't require additional filtering).