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Deinterlacing for down-scaled web video?

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Craig Reed
Deinterlacing for down-scaled web video?
on May 25, 2006 at 6:12:49 pm

I have heard arguments for both sides of this in other forums, though neither were authoritative. So I pose it to you here, and if anyone can cite a source, that would be great. Short of that, I'll just have to do a bunch of tests myself.

In preprocessing, is it necessary to deinterlace video coming from an interlaced source if you are going to scale it down in size? Does it matter what percentage you scale it down when deciding to deinterlace or not?

In other words, depending on the tool used to scale size, (we are using FlixPro, Cleaner, and Compressor for various jobs), one way or another, scan line info is going to be thrown away or merged. So if I am scaling down to 50% original size or less, will interlacing comb artifacts still show up in the output?

I ask because, particularly in FlixPro, deinterlacing adds a ridiculous amount of time to the process.

Thanks,
-Craig


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cow
Ed
Re: Deinterlacing for down-scaled web video?
by
on May 25, 2006 at 7:36:22 pm

Interlacing will look horrible on a progressive computer monitor, no matter how scaled the video is.
Do a short test to see just how bad.
Ed


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daniel_l
Re: Deinterlacing for down-scaled web video?
on May 26, 2006 at 10:04:14 am

I would always deinterlace, preferably adaptive, over just a resize.

Here's a great page illustrating the potential issues.

http://www.100fps.com/


DL

Video AllSorts


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Craig Reed
Re: Deinterlacing for down-scaled web video?
on May 26, 2006 at 6:14:31 pm

Thanks, Daniel.
The site you referenced mentions that if you resize video down to 1/2 or less, the effect is the same as using a blend deinterlace setting, (though all their work was done with Virtualdub, a tool we do not use on Mac).

So I did my own tests, just to see for myself.
See my test results here.

The results were very revealing. I scaled the video down to half size, as I proposed(320x240).

Interlacing artifacts were very evident if you simply resized the video. The best deinterlacing settings I found in Cleaner were "Automatic" with "Adaptive" turned on. Adaptive means it only applies deinterlacing were it is necessary. Blend mode merges the two fields and gives a sort of double-image. but it doesn't look anything like the simple resize results.

Thanks,
Craig


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