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Old August 26th, 2007, 11:15 AM   #1
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General question about deinterlacing

Hello all,

I did a quick search in case this thread had already been created. I did not find anything that closely resembled my question, but I apologize if it has been answered/is posted in the wrong forum/is a very naive question.

I understand what it means for footage to be interlaced and deinterlaced, however, I don't really know WHEN to deinterlace. It is to my understanding that video being played back on a tv should be interlaced and video playing back on a computer should be deinterlaced. Is that correct?

Presuming that's true, if I'm making a DVD that is intended to be played back on TV, then I *should* leave the footage interlaced. This leads me to ask: what about the DVDs of Hollywood-made movies that I buy at the store? Those DVDs look fine on a tv and on a computer. So does 'Hollywood' deinterlace or what?

I feel like this is a simple question, but I truly appreciate any and all help I can get to understand this. It could very well be the case that I haven't properly conceptualized deinterlacing. Thanks!
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Old August 26th, 2007, 12:48 PM   #2
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Hi Sunny,

Hollywood films are shot (mostly) on film (24 frames a second, or 25 frames a second) or on digital video taping at 24p or 25p (deinterlaced, or 'the film mimick look'). Deinterlaced footage has the same movement cadence as film, that's why people mostly deinterlace.
It's another look if you compare them artistically. Interlaced seems to move a bit faster, or is better with fast movement, but deinterlaced looks more filmlike, and most of the time better for narrative work.

So the answer to your question is: Hollywood shoots deinterlaced (as you can, if you have the proper video camera that has that function), so they don't need to deinterlace their dvd's (although I don't know the last thing for sure)

I hope this helps,
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Old August 26th, 2007, 02:00 PM   #3
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Ah, okay, that makes sense. I typically use my GL2 in 'frame mode' which I always thought was deinterlaced. I don't know if I'd be better off filming under normal mode and then converting to 24p in post. I guess that's something I need to play around with. Either way, thanks again for clearing things up.
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Old August 27th, 2007, 02:51 AM   #4
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Hi Sunny,

do you have a GL2 PAL or not?
If you have a GL2 NTSC then it's better to shoot 60i and convert to 24p in postproduction, because the frame mode of the GL2 NTSC is 30p. And that can't be transferred to 24p.
If you have a PAL GL2 (which is called the XM2, so I don't think you have that one), if you shoot frame mode, it's 25p (but with a slight resolution drop). 25p can be very easily converted to 24p.
I have a XL1s PAL (I live in Belgium) and I always shoot frame mode.

Best regards,
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Old August 27th, 2007, 04:12 AM   #5
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Below is an interesting site about deinterlacing:
http://www.100fps.com/
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Old August 27th, 2007, 01:14 PM   #6
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There is a difference between deinterlacing and shooting true progressive images.

If you shoot interlaced, you have 50/59.97 fields a second. But in a way, half the information is missing in each field. De-interlacers have to guess that information... therefore deinterlacing doesn't really work (as in, it's not a perfect process). Though the really good de-interlacers will do a decent job.

Interlaced cameras also tend to use row-pair summation, which is a way of dealing with interlaced artifacts and increases sensitivity. This lowers vertical resolution.

Progressively-captured images don't have these problems.
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Old August 27th, 2007, 08:48 PM   #7
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Its just a different look. Remember that interlaced footage is 'twice' as smooth as deinterlaced. De-interlaced is slightly choppy, 24p even more so. Both formats will play fine on both TV's and Computers
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Old August 28th, 2007, 12:28 AM   #8
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Thank for the input, everyone. I have a GL2 NTSC. I mostly do work for local bands (filming live shows and putting them on DVDs). I like the grainy look generated by frame mode as opposed to shooting at 60i. This week I'll shoot some footage at 60i and convert it to 24p in post and see how that turns out.
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Old August 28th, 2007, 10:30 PM   #9
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How would you go about converting from 60i to 24p in Final Cut? I'm a GL2 user also, and have been shooting in frame mode, I'm just curious how to convert so I can test and see a difference.
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Old August 29th, 2007, 08:35 AM   #10
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I attempted to convert 60i to 24p using Magic Bullet in After Effects. I applied the Magic Bullet deinterlace and exported the video. Nowhere in the MB effects toolbar did I see anything or any mention about 24p though, which I thought was strange. When I watched the exported video, it turned out extremely choppy and significantly worse than frame mode (30p). Is there a better way to convert? Are there more settings in MB that I need to tweak?
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Old August 29th, 2007, 12:20 PM   #11
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It's Just Not Advisable

Interlaced videos look much better on a standard definition TV, and that's all there is to it. Deinterlacing is only going to make your video and/or blurry. Hollywood movie producers have to jump a lot of hoops to get rid of the jerkiness in 24fps video, but they only do it because they don't have a choice. You do!
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