Deinterlace or preserve interlace (DVD to AVI)?

[Mildew]

I'm converting some DVDs to AVI (Xvid and DivX). I'm experimenting with Handbrake and DivX 6, but I've read some contradictory information about encoding from interlaced sources.

The DivX 6 setup guide recommends the following:

You can encode the video as progressive or interlaced. If your original source is interlaced, then encoding it as interlaced may result in a better looking picture, although it may increase file size. Similarly, encoding the video as progressive if the source is progressive will be benefitial.

The middle option allows you to "De-interlace source", which is just a way to convert the interlaced source into a progressive one. This is not really recommended, as it can lower picture quality.

But the complete DivX guide says this:

There are some circumstances where it is desirable to maintain the original interlaced fields discreetly so as they can be recreated without artifacting for display on an interlaced device. One example of such a situation is playback via a DivX Certified device to an interlaced television.

If your source video is interlaced you should select to de-interlace all frames to progressive unless you have a specific reason for preserving interlacing. Encoding as interlaced requires substantially higher bitrates in order to achieve equal perceptual quality to progressive content.

The first one says not to de-interlace because it'll lower the image quality of the resulting AVI file. But the second one says that you should de-interlace because maintaining interlace wastes CPU cycles. You should maintain interlace if you're going to play the AVI on a DivX certified machine.

Well, what if I want to watch the AVI on my computer and on a DivX capable DVD player?

Will deinterlace really degrade the quality that much? Should I deinterlace or maintain interlace?

[havema-1]

You should keep the material interlaced if you intend to playback it on an interlaced TV. Interlaced material has smoother motion on a TV monitor. Watching progressive material on a TV gives me headache

You should deinterlace if you intend to playback it only on a computer. Interlacing lines look awful on a computer monitor!

If you intend to playback the material on a computer monitor OR a TV, you must make a choice. If you deinterlace, you effectively throw away as much as 50% of the input... Many computer apps can deinterlace on-the-fly (and then you can even choose which deinterlacing method to use) so keeping the material interlaced might be OK even then. But some users might not be knowledgeable enough to do that and may complain about the ugly comb lines on their computer displays... So sometimes it might be best to deinterlace if you intend to playback the material on a computer monitor OR a TV.

[drewzor]

I was once told - and i dont know if this is right - but its always worked for me..

If its progressive and you want to watch it on tv
interlace the footage bottom field first

If its interlaced and you want to watch it on tv
Interlace top Field First

If its Interlaced and you wanna watch it on pc
Progressive de-interlace

[sdm]

I would de-interlace it, even if I'm going to watch it on TV
(sorry, I'm not gonna get specific about my reasoning)

note: don't choose de-interlace for progressive stuff (like most movies).

-- sdm.