crop/resize and preserve interlacing

[tonemgub]

Is there a way to use AVISynth or VirtualDub to crop a .AVI VHS Capture and resize it and at the same time preserve the interlacing (not mess it up). Do I just do it or do I need to do something special?

[daamon]

VirtualDub should be able to crop and / or resize without affecting the interlacing. If resizing, use the "Lanczos" filter.

Just in case...:

"crop" = hiding parts of the picture so they aren't displayed. This will leave a border around the remaining image.

I can't see a "crop" filter in VirtualDub - one may be available. I achieved the same by adding four "fill" filters - one for each border, and filling with a colour of your choice.

"resize" = changes the size of the image, effectively zooming in (maing it bigger), or out (making it smaller) on the image.

[junkmalle]

Resizing interlaced video never gives perfect results. But the best way to do it is to separate the fields, resize, then interlace them back together.

The resize filter in VirtualDub has an "interlaced" option that does this automatically.

To do it manually you could use the following procedure:

In VirtualDub select the deinterlace filter and use the "unfold fields side by side" option. Then resize (note your video is twice as wide and half as tall now so keep that in mind). And finally use another deinterlace filter with "fold side-by-side fields together" selected.

There are similar methods in AVISynth. Use SeparateFields, Lanczos4Resize, then Weave them back together.

[manono]

Simple AviSynth Interlaced resizing:

AssumeTFF()#or AssumeBFF() if bottom field first
SeparateFields()
Crop(xx,xx,xx,xx)
LanczosResize(xxx,xxx)#use resizer of choice. Lanczos4Resize would not be my choice
AddBorders(xx,xx,xx,xx)#if necessary
Weave()

Much better, if slower:

LeakKernelBob(Order=1)#slower but slightly better is TDeint(Mode=0)
Crop(xx,xx,xx,xx)
LanczosResize(xxx,xxx)#use resizer of choice
AddBorders(xx,xx,xx,xx)#if necessary
SeparateFields()
Selectevery(4,0,3)#Or SelectEvery(4,1,2) if BFF
Weave()

Full discussion:

http://forum.doom9.org/showthread.php?t=90950&highlight=interlaced+resize