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Shooting 60i for 60p slo-mo


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#1 Tim J Durham

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Posted 03 August 2005 - 09:42 AM

Hi,
I have not tried this yet, but I'd like to be able to shoot in 24p (not 24pA) and intercut some 60p slo-mo footage. Has anyone tried this?

I'd love to hear about any issues it may present in Final Cut or any other link in the chain.

Thanks in advance.
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#2 David Mullen ASC

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Posted 03 August 2005 - 10:19 AM

Do you mean that you want to shoot in 60i and convert it to 60P then play it back at 24P with a 3:2 pulldown for a final 60i product?
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#3 Tim J Durham

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Posted 03 August 2005 - 12:36 PM

Do you mean that you want to shoot in 60i and convert it to 60P then play it back at 24P with a 3:2 pulldown for a final 60i product?

<{POST_SNAPBACK}>


Yes, that's right David. I've not yet abandoned shooting in 30p as it is for TV delivery so that may be how it works should the 60p slo-mo work better with the 30p. As it is, my b-cam is my XL-2 which does NOT have free-run TC in 24p, but DOES in 30p. Not having it will create a problem for times when we need the two cams (nearly as possible) synched to time of day TC. It's not dialogue that needs to be synched, only action so precise synching is not crucial. Just ballpark.

What do you think about 30p? I don't think I've ever seen it on the tube and I can't test because I don't get the SDX900 until two days before the shoot. Whatever I decide will have to be done before I can pick up the camera..

It IS football practice so alot of panning and fast-moving action, that's why I was still leaning toward 30p. I've got til Saturday to decide.
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#4 Brian Wells

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Posted 03 August 2005 - 01:27 PM

...I don't think it's necessary to convert to 60p at all, really.

60i is kind of like 60p except it is lower in resolution. So, converting to 60p isn't really doing anything besides introducting an additional compression stage.

What you'd need to do is capture the 60i, insert in a 24p timeline, then "speed change" it to 40%. This should evenly distribute the 60 fields across 24 frames in the timeline. Render, playback. Voila.

BW
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#5 David Mullen ASC

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Posted 03 August 2005 - 04:54 PM

30P is fine if you don't want a 60i look but only plan on releasing the material in 60i (NTSC or HDTV) or for progressive-scan display devices (like on the internet) -- but 30P is not a good idea if a film transfer is possible or PAL version is needed.
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#6 Tim J Durham

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Posted 03 August 2005 - 05:56 PM

30P is fine if you don't want a 60i look but only plan on releasing the material in 60i (NTSC or HDTV) or for progressive-scan display devices (like on the internet) -- but 30P is not a good idea if a film transfer is possible or PAL version is needed.

<{POST_SNAPBACK}>

Yes, domestic TV Land only, output to DVC-Pro50 or Digi-Beta. It's a taster tape fo a show proposal so it will likely never see the light of day. Only pitch meetings and they happen in dark caves in the bowels of Hollywood, or so I've been told.
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#7 Alvin Pingol

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Posted 03 August 2005 - 07:17 PM

>>60i is kind of like 60p except it is lower in resolution. So, converting to 60p isn't
>>really doing anything besides introducting an additional compression stage.

Not quite. Converting fields to frames (60i --> 60P) is something I do a lot of and have found it to be very useful. Interlaced footage is a pain to work with since the only proper way of viewing it is at full speed on an interlaced display. Converting fields to frames gives you much more flexibility. Plus, if compression is an issue, you can always do the conversion uncompressed.

60i and 60P are different beasts. When interlaced, two points in time are represented in one frame. This can cause major headaches when dealing with speed conversion, since the majority of software alters speed via framerate adjustment. Because each interlaced frame depicts TWO points in time, most software automatically deinterlaces the footage unless you tell it not to, in which case the interlace scan lines will be left in. This does not look pretty; when viewed on an interlaced set, each "frame" has its own sort of motion to it, an artifact of having those interlace lines still there.


>>What you'd need to do is capture the 60i, insert in a 24p timeline, then "speed
>>change" it to 40%. This should evenly distribute the 60 fields across 24 frames
>>in the timeline.

This assumes the software is converting 60i to 60P! You cannot just 'evenly distribute' fields, for one field is only half a frame. This is where fields to frames interpolation comes in, after which 60P can then be evenly distributed across 24 frames, at 40% speed like you said.
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#8 Brian Wells

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Posted 03 August 2005 - 09:59 PM

Converting fields to frames (60i --> 60P) is something I do a lot of and have found it to be very useful.

I'm trying to understand what you're saying, but am coming up short. Please let me know your procedure for converting 60i to 60p, because right now it is not clear.

Thanks,
BW
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#9 Tim J Durham

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Posted 03 August 2005 - 10:40 PM

I'm trying to understand what you're saying, but am coming up short. Please let me know your procedure for converting 60i to 60p, because right now it is not clear.

Thanks,
BW

<{POST_SNAPBACK}>


I was calling it 60p but it's not actually, it's de-interlaced 60i:

http://www.joesfilte...einterlacer.php

But I was planning to do what you proposed a couple of posts back, I was just adding the extra step of de-interlacing it first, then laying it into the 24p (actually 29.97) timeline and stretching it just as you described only 50% instead of 40%. I'm not shooting 24pA, Infact I'm leaning toward 30p due to other problems I'm having currently. AND I'm not an editor, so I'm still a little foggy on how it's all gonna work out.

I guess I'd say I'm on the front side of the learning curve on 24p. I shoot it semi-frequently, but I don't have to deal with it after that. Until now.

So thanks for the comments. Every little bit helps. The worst part is- there is stuff I happen upon, after having reached a point where I thought I had a grip, only to be reminded of stuff I didn't even know that I didn't know. But nobody ever learned anything by succeeding all the time.

It's 11:39pm and I'm drinking coffee.
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#10 Brian Wells

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Posted 03 August 2005 - 11:48 PM

I shoot it semi-frequently, but I don't have to deal with it after that.

I would venture to say we're in the same boat, Tim. Just hand the tapes over when I'm done. I mean, I have a DVX100a sitting here. I have FCP on my laptop (coincidentally with the Joe's filters I bought two years ago...) But, to be quite honest, I've never even tried the method I suggested! Maybe I should give it a spin before making suggestions!

... nobody ever learned anything by succeeding all the time.

I'm interested in learning any approach which works...

Oh, and I'm drinking a Coke. :rolleyes:

BW
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#11 Thomas Worth

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Posted 04 August 2005 - 02:06 AM

I was calling it 60p but it's not actually, it's de-interlaced 60i:

<{POST_SNAPBACK}>

Technically, the resulting footage after deinterlacing is 60p, although at a decreased resolution. That footage can then be played back at 24p to simulate slow motion. If you want to record back to DV tape or intercut with 24p footage with 3:2 pulldown (e.g. NOT 24pA footage), you will need to introduce a 3:2 pulldown into the 24p slow-mo footage. Converting 60i to 60p, then to 24p, then to 29.97 (24p w/3:2 pulldown) can be done with After Effects.

Check out my article on slow motion here:

http://rarevision.co...slow_motion.php

That may help answer some questions.
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#12 Tim J Durham

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Posted 04 August 2005 - 07:06 AM

Technically, the resulting footage after deinterlacing is 60p, although at a decreased resolution. That footage can then be played back at 24p to simulate slow motion. If you want to record back to DV tape or intercut with 24p footage with 3:2 pulldown (e.g. NOT 24pA footage), you will need to introduce a 3:2 pulldown into the 24p slow-mo footage. Converting 60i to 60p, then to 24p, then to 29.97 (24p w/3:2 pulldown) can be done with After Effects.

Check out my article on slow motion here:

http://rarevision.co...slow_motion.php

That may help answer some questions.

<{POST_SNAPBACK}>


BINGO! Man I was wrackin' my brain trying to figure out where I'd read that article!


"You said that, Karl? What a guy!"

-Joseph Bologna (King Kaiser) from "My Favourite Year"


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#13 Alvin Pingol

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Posted 06 August 2005 - 06:19 PM

I'm trying to understand what you're saying, but am coming up short. Please let me know your procedure for converting 60i to 60p, because right now it is not clear.

<{POST_SNAPBACK}>


Hi, I'm hoping Thomas Worth's article may have cleared up some things for you, as it details the same thing I'm describing (60i to 60P to 24P).

My process involves taking the 60i footage through a custom script written for AVISynth, a very handy tool that unfortunately scares most people away because a GUI for it doesn't exist. Once you read the script documentation, it becomes quite easy. Anyway, the script takes the 60i footage and applies a process called Bob deinterlacing, which (1) splits the 60i footage into 60P, thereby doubling the framerate and reducing the vertical size by two, (2) resizing the 60P back up to full frame [bicubic interpolation], and (3) shifting the even and odd frames down a half pixel and up a half pixel, respectively. This is where "bob" comes in; the frames are bobbing up and down to counteract the natural location of even and odd fields, creating a fairly steady image.

AVISynth homepage

I then render the process in VirtualDub.

Hope this helps.
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#14 Thomas Worth

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Posted 08 August 2005 - 05:45 AM

My process involves taking the 60i footage through a custom script written for AVISynth, a very handy tool that unfortunately scares most people away because a GUI for it doesn't exist.

<{POST_SNAPBACK}>

I've tried this, and it works pretty well. But you're right, the lack of a GUI throws some people off. The nice thing about this technique is all the software needed is free!
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