How to crop and resize interlaced material

[arnie.d]

I have a DV file that has black bars at the side and top. What is the proper way to crop and resize interlaced material? I want to resize with lanczos4resize. Should I use somthing like this:

seperatefields()
crop()
lanczos4resize(720,288)
weave()

Or are the internal avisynth filters suitable for interlaced material?

[wonkey_monkey]

You need to bob, resize, separatefields, selectevery(4,0,3) and weave (with appropriate assume(b/t)ffs).

If you simply separatefields and resize, your lines don't maintain their original positions in the interlaced frame.

David

[arnie.d]

Thanks for your help. So is this about right?

ConvertToRGB()
Bob(0.0, 1.0)
Crop(0,2,-12,0)
Lanczos4resize(720,576)
SeparateFields()
Selectevery(4,0,3)
Weave()

The original clip is bff. Should I add assumebbf or is it not necessary?
Also, can you please explain what Selectevery(4,0,3) does?

[Guest]

Are you sure it is BFF? PAL DV is TFF if I remember correctly.

The code after your resize takes the bobbed stream and reinterlaces it to the unbobbed frame rate.

[wonkey_monkey]

Are you sure it is BFF? PAL DV is TFF if I remember correctly.

You don't, I'm afraid :) It's BFF, which can cause headaches for me at work :(

Stick an assumebff + bob at the end temporarily to test the output. If it judders, AviSynth has made a bad assumption and you'll need to add an assume before the bob, or the separate, or the weave (there must be some logic to it but I've never found it!).

David

PS Consider a better bobber than bob, like yadif. You should get a noticeably better output.

[zambelli]

Crop(0,2,-12,0)
Lanczos4resize(720,576)
Doesn't this effectively change the aspect ratio though?

[arnie.d]

Yes, but that's no problem.