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Old March 20th, 2007, 10:34 AM   #1
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De-interlace or not to De-interlace

Howdy,

When is it good to de-interlace and when is it good not to?
I film in HDV (capture in DV) with a Sony HDR-FX1 and use FCP for editing if that helps at all.

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Old March 20th, 2007, 10:56 AM   #2
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If you intend to view your footage on a native progressive display (LCD, etc.), then de-interlacing makes sense. If you intend to view your footage on a native interlaced display (CRT television), it doesn't make sense to de-interlace, unless you are doing it to achieve an effect (like imitating film).
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Old March 20th, 2007, 01:15 PM   #3
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Thanks for your reply, in what way would it imitiate film to de-interlace?
Thanks
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Old March 20th, 2007, 01:50 PM   #4
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The de-interlacing in itself does not imitate film, but in order to mimic the motion of film de-interlaced looks closer to film then interlaced.
That is: interlacing is fields interlaced together to form what we precieve as frames, odd and even fields. When watching interlaced you get more temporal resolution and the motion looks more "real". The "half-frame" is updated every 50th of a second (in PAL that is, taking for granted you're a PAL-guy) and in film you usually record 24fps. So de-interlacing can bring you closer to film as you can make whole "progressive" frames out of your interlaced footage.

I hope I didn't confuse you, and if my explantion is insufficient you can try to wiki it and I'll bet you won't be dissapointed.
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Old March 20th, 2007, 02:47 PM   #5
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If you do not deinterlace, which in many situation will provide a better result, be sure that your DV output encoder is using the "lower field first" interlace mode. Upper field first, at least in Premiere, creates a messy looking video.
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Old March 21st, 2007, 05:11 PM   #6
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Quote:
I film in HDV
Can't you use one of the progressive HD modes in the first place? HD is made to deal with progressive video, so if you shoot HD you can just as well shoot progressive from the beginning (or can't you with HDV???)
De-interlacing is always sub-optimal unless the output is viewed on progressive displays only and needs to be compressed really well (like mpeg4 with low bitrates)
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Old March 22nd, 2007, 11:50 AM   #7
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HD is both progressive and interlaced. The FX1/Z1U has a fake progressive mode, but very few people like it.

Chris, if you're shooting HDV and still work SD at the moment, I would suggest you stay interlaced - as pointed out above, deinterlaced looks better only on progressive monitors, but makes your video weird looking on regular CRT based screens (you loose "temporal resolution" or motion resolution). I did some testing myself (edited in HDV and output to SD DVD) and I decided to stay interlaced). Besides, if your footage gets to be watched on a progressive video monitor, either the DVD player or the monitor itself will do the deinterlacing for you anyway.

A good time for deinterlacing is when you prepare your footage for the internet.
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Last edited by Ervin Farkas; March 22nd, 2007 at 11:54 AM. Reason: typo.
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Old March 25th, 2007, 08:04 PM   #8
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Originally Posted by Ervin Farkas View Post
as pointed out above, deinterlaced looks better only on progressive monitors, but makes your video weird looking on regular CRT based screens
i wonder though what percentage of people still use CRT monitors. i'd imagine it's very small.

and can you explain why progressive looks weird on CRT (as opposed to on an LCD or plasma display)
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Old March 26th, 2007, 05:51 AM   #9
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This site is so unbelievably helpful. Thank you all for the time you took to explain things.

Ervin, I don't think I understand what 'fake progressive mode' means. I use the FX1 and I know it isn't true progressive. What exactly is the difference?

Thanks

Last edited by Chris Westerstrom; March 26th, 2007 at 05:52 AM. Reason: mispelling
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Old March 26th, 2007, 03:30 PM   #10
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I dunno if I think the percentage of people that still use CRT monitors is "very small". It probably depends where you are at. And where I'm at the HUGE majority of people are still using CRT.....basically because it's cheaper. So I'd say, look at your market and see what THEY are using.
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Old March 26th, 2007, 04:10 PM   #11
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A true progressive camera (or 'native' progressive) takes one complete picture of the footage you're shooting and stores it on some kind of digital media (tape or SD card or hard drive or what have you). If you shoot 24 frames a second that's 24 complete whole pictures being captured and saved to digital media every second. That's a lot of information going through at a very fast rate.

When you shoot interlaced you only need to capture half the picture so the data load is less. You then take this footage and de-interlace it in post using a pulldown method. After Effects can do it, Vegas can do it and I'm sure a lot of others can do it but I've only tried these two.

Camera companies offer a pulldown progressive mode in some of their cameras. Different cameras use different methods of pulldown. I only remember two methods but I could be wrong about that. When a camera does this, it's called 'fake' progressive mode.

You can probably chalk this all up to the power of an industry buzzword.

P.S. I love my CRT's (all four of them).
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Old March 26th, 2007, 04:19 PM   #12
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Originally Posted by Chris Westerstrom View Post
This site is so unbelievably helpful. Thank you all for the time you took to explain things.

Ervin, I don't think I understand what 'fake progressive mode' means. I use the FX1 and I know it isn't true progressive. What exactly is the difference?

Thanks
I have the FX1, of course NTSC. If in my pricture profiles, I select Cineframe 24, or Cineframe 30, I get a "pseudo" progressive result. Supposed to look more like film. It does have that juttery look. With careful filming, and very slow pans, you might sneek something through.

I'm guessing you might be PAL and be shooting and FX1e, so I don't know what options you have. But my understanding of PAL is that you shoot at 50i with FX1. I assume that is true of HDV also. I have heard that you can actually do a pretty nice "film look" in PAL cameras by deinterlacing 50i in post and adjusting time to run at 24fps. Don't ask me technical aspects of all this..
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Old March 26th, 2007, 06:54 PM   #13
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Originally Posted by Chris Westerstrom View Post
Ervin, I don't think I understand what 'fake progressive mode' means. I use the FX1 and I know it isn't true progressive. What exactly is the difference?
In short it's throwing away one field and doubling the other one. I don't think I will ever be able to explain it better than Adam Wilt: see http://www.adamwilt.com/HDV/cineframe.html
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Old March 31st, 2007, 01:00 PM   #14
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What if your exporting to DVD? Deinterlace, or not?
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Old April 1st, 2007, 10:44 AM   #15
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Unless your DVD will be watched exclusively on a progressive display (LCD, plasma), stay interlaced. Even if your final product will be viewed on a progressive monitor, you can still stay interlaced, the display will take care of it. The advantage of going progressive via software is that, if you use a high quality deinterlacer that makes a good motion prediction, you might end with a better image (not having to rely on the quality of the DVD player's or the display's deinterlacer circuit).
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