resizing 16:9 interlaced source

[SimonSez07]

there are many instances where you have an interlaced (not telecined) dvd or dv source in anamorphic widescreen that you need to resize to the proper aspect ratio before encoding. most people would simply deinterlace, resize, and encode as progressive, but that looses quality and then you have a final product that is 29.97 fps progressive (not ideal for display on a tv).

i would much rather leave the video interlaced and encode as such to preserve the most quality. for instance encoding to svcd is a perfect example since mpeg2 can handle interlaced source and you will be viewing the final video on a tv.

i came across this avisynth script which will correctly resize to svcd resolution while preserving the video perfectly interlaced.

LoadPlugin("MPEG2DEC.DLL")
MPEG2Source("Video.d2v")
Bob
BilinearResize(480,360)
AddBorders(0,60,0,60)
DoubleWeave
SelectOdd
SelectEven


this method produces far superior encodes as long as you encode with the 'interlaced source' option enabled

for square pixel encodes you would simply replace BilinearResize(480,360) with BilinearResize(640,360)

[lamer_de]

Are there interlaced NTSC DVDs? I live in a PAL country and i'm just curious. Movies are TC'ed, and I think even most series are if they're released on DVD (or some Hybrid mix ;p )

For DV it's clear, but it's even stated in the FAQ that you shouldn't deinterlace if you use a format which can handle interlacing (=mpg2).

CU,
lamer_de

[SimonSez07]

i have come across dvds that are truly interlaced not ivtc'd like sat night live episodes or live concert performances or extra content on movie dvds like behind the scenes interviews just to name a few. but definatly a perfect candidate is dv content that was shot in anamorphic or 16:9 mode.

and yes, indeed, if people would read the guides they would know not to deinterlace when the codec supports interlaced encoding, but if you need to resize the video vertically (anamorphic sources) and you did not know how to properly resize interlaced content, you would have little choice. and i think this is a common scenario, so i hope this avisynth script helps.

-simon

[scmccarthy]

I have given up understanding Weave() and DoubleWeave(). It has to do with fieldbased vs. framebased, which now we know has nothing to do with interlaced vs. progressive and which no one has understood, although clearly it is important. This makes me favor Simon Walters ViewFields() and UnViewFields() which I understand since I played with converting it to avisynth2.5 in YV12 as he now offers it on his site (I hope). What it does is simple and straightforward, although the user is responsible for knowing the the source is interleaved. (Telecine is interleaved too, if you intend to leave it telecined.) All you do is use ViewFields(), Resize, and UnViewFields(). Something like this:

ViewFields()
ResizeLanczos(640,352)
UnViewFields()

This is wrong, because I don't know aspect ratios for interlaced material, but although the aspect ratio would be wrong, it would still be interlaced if we started with an interlaced source.

Personally, I like that ViewFields lets you resize to the target size. Crop after UnViewFields() or before ViewFields() if you know what you are doing.

Stephen