DGIndex deinterlace/croping interlaced NTSC

[XiOUS]

DGIndex shows this info when pressing F5:
AR: 4:3
Frame Rate: 29.970 fps
Video Type: NTSC
Frame Type: Interlaced
...

I have tried to save the project with "Video" -> "Field Operation" set to "None" and to "Forced FILM". I then create an .avs file as below:
LoadPlugin("C:\DGDecode.dll")
LoadPlugin("C:\Decomb.dll")
mpeg2source("G:\DD51\ddi1.d2v")
fielddeinterlace()
crop(0,38,0,-38)
lanczosresize(720,480)
ResampleAudio(44100)
"DGDecode.dll" I've taken from DGIndex files and "Decomb.dll" I've taken from DoItFast4U program as I couldn't find it in DGIndex folder or anywhere else. I guess I need to use it for "fielddeinterlace()" to work.
My problem is that something is wrong because when I add "LoadPlugin("C:\Decomb.dll")" and "fielddeinterlace()" to my .avs file, CCE will load it but the duration shows up as only ~10s when otherwise it shows up as ~35s.
I've also tried "SmoothDeinterlacer.dll" adding this lines to my .avs:
LoadPlugin("SmoothDeinterlacer.dll")
SmoothDeinterlace()
with same result (shows up with ~10s duration).

How can I deinterlace my interlaced NTSC in a proper way?
Because if I use my .avs without the deinterlace-stuff my final VOB will have these irritating horizontal lines in the picture.

[Cyberia]

Some suggestions:

You should be using a Field Operation = "None".

Loose the ResampleAudio command. There is no audio in the script anyway.

Make sure these are the latest versions of your dll's. Decomb should be ~v5.21 and DGDecode should be ~v1.0.12.

Try adding a "ConvertToYV12()" after FieldDeinterlacer. Try the other Converts.....ToRGB32 and ToYUV2.

Try KernelDeinterlace.

[XiOUS]

Ok I now use Video" -> "Field Operation" set to "None" and Decomb v5.21 and DGDecode v1.0.12 with the following .avs:
LoadPlugin("C:\DGDecode.dll")
LoadPlugin("C:\Decomb521.dll")
mpeg2source("G:\DD51\ddi6.d2v")
fielddeinterlace()
crop(0,64,0,-64)
lanczosresize(720,480)
ResampleAudio(44100)
The resample audio I've taken from Getting the best out of CCE (http://www.doom9.org/mpg/cce-advanced.htm) The last line is used to trick CCE into believing that the input file has an audio track. Otherwise CCE would crash when being run on an AMD processor. ( I have an AMD CPU).
It seems to work now anyway, thanks for the help.

The reason that I use crop/lanczosresize is that I want to crop the black bars in my 4:3 source and make it 16:9 (16:9 is selected in CCE). I've used DGIndex clipping feature to see how much to crop so that the black bars is gone completely.
My question is that if the black bars take up lets say 50% of the picture (picture take up the other 50%) and I cut them completely using "crop(0,120,0,-120)" (480/2=240, 240/2=120). Then using "lanczosresize(720,480)" and encoding it with 16:9 (in CCE) will this change the picture like dragging it out (to lets say 400) or will it have the same height (240)?

If so is there some general way in cropping 4:3 to 16:9?
My guess is that 16/9 = 720/x -> x = 405 so a height of 405 gives true 16:9. 480-405=75, 75/2=37.5, so then I can use "crop(0,38,0,-38)" to get nearly true 16:9 (can't use 37.5 I guess)? Is this right?
I've tried some different cropping and to "crop(0,60,0,-60)" seems to be the best as the picture will have the same (or very close) height as original.

What do "ConvertToYV12()" do?