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Fields, Interlacing, and Horizontal Motion

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jamski
Fields, Interlacing, and Horizontal Motion
on Apr 11, 2007 at 1:34:11 pm

I'm working on a spot and am having issues with an effect I'm applying.

I have a bunch of shots, shot on white, that I'm trying to "slide" across the screen in a constant horizontal motion, given the effect that it's one long right-to-left pan.

However, I'm seeing what I assume are interlacing anomalies around the edges of the shots due to the slow, constant horizontal motion.

If I scrub thru the clip frame-by-frame, the edges are clean. But if I play the shot in realtime, on the TV monitor, the shots are hard to look at.

Take a look at this short sample. Download this clip and plop it on a SD Premiere timeline and play it. Tell me if you see the same thing I see.

The shots were shot with a Panasonic Vericam at 30P and acquired via SDI with a Panasonic AJ-HD1400 deck. The clips were then affected in a 29.97fps 720x486 composition in After Effects.

I tried lower fields first, frame blending, etc., all have the same interlacing effect when played.

Is this just a limitation of traditional interlaced TV? Is there anything I can "set" to rectify this issue? Should it have been shot or acquired differently to avoid this situation?

Thanks.

Clip: http://www.rynopro.com/stuff/TEST.mov
It's 68MB.

--
James Orlowski
RYNO Production, Inc.
http://www.rynoproduction.com
800-860-7966


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Jeff Brown
Re: Fields, Interlacing, and Horizontal Motion
on Apr 11, 2007 at 3:47:06 pm

James,
I would hazard to say that what you are seeing is a combination of 2 things: the artifacting of 30P images moving horizontally at a "wrong" speed, combined with watching progressive images on an interlaced display-- which will make it look even worse. Take a look a the boy with the hammer: notice how much motion blur is in the original footage? That's what you need to mimic to make the horizontal move look right. Something like re:Vision's SmartBlur, or maybe even simple horizontal motion blur should help. Make sure AE knows the source footage is NOT interlaced. Sounds like your output is interlaced (SD-TV?).

If the destination is SD video/TV, the best source might have been to shoot 60P, which would have more temporal resolution to hold up going to 30i. But it's also an aesthetic choice.

Play with that mo-blur, you should find something that helps.

-jeff


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jamski
Re: Fields, Interlacing, and Horizontal Motion
on Apr 12, 2007 at 2:44:48 pm

Thanks for the input.

For the heck of it, I tried this same effect in Premiere using the same clip files.

And, it seems to be much better.

My question is why? Why does the same right-to-left movement in Premiere do so much better than After Effects?

There's got to be some setting in AE that would let me do this movement in that app; doing this effect in Premiere wasn't as easy as it is creating it in AE.

Here's the clip: http://www.rynopro.com/stuff/TEST2.mov
This one is 175MB for some reason.


--
James Orlowski
RYNO Production, Inc.
http://www.rynoproduction.com
800-860-7966


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Jeff Brown
Re: Fields, Interlacing, and Horizontal Motion
on Apr 19, 2007 at 8:44:45 pm

Did you try what I suggested in AE?


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jamski
Re: Fields, Interlacing, and Horizontal Motion
on May 2, 2007 at 12:25:27 pm

Yea, I tried quite a few things. All had the same issues.

But I did do the same move with the same video clips in Premiere, and the result was MUCH better. I'd like to know why, because that shows that this move can be successfully done with these video clips, just not in AE with my current settings. (See the two video clips samples in the above post.)

There's got to be a reason that AE has such an issue in this situation. I wonder if there's a setting I need to adjust.

I thought it might have been because of the 30P content, but standard 60i BetaCam footage also has the same odd interlacing effect when rendered in AE.

Any other thoughts?


--
James Orlowski
RYNO Production, Inc.
http://www.rynoproduction.com
800-860-7966


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Jeff Brown
Re: Fields, Interlacing, and Horizontal Motion
on May 2, 2007 at 2:29:32 pm

I would have to suggest carefully checking all your AE input/output settings. If you are seeing interlacing artifacts, it is from a misplaced setting somewhere. AE handles interlaced footage just fine. It has since version 1.2, at least...

Or, just use Premiere if it works for you. (to avoid any dead-horse-beating...)

-jeff


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