Help with proper AfterEffects settings!

ericmanche

New member
Hello,

I’m a long-time reader, first-time poster.

I have a question regarding an issue I’ve been running into doing special effects work for a feature film. The effects are being done in After Effects CS3, and the effects themselves comprise a large portion of the film (probably about 25 percent of all shots are vfx shots). We’re doing explosions, laser blasts, earthquakes, head decapitations, compositing, and slo-down. I’m nearing completion with effects, and am finally now beginning to deal with this issue.

We shot the film with a DVX-100B, on 24p NON-ADVANCED and are editing with Final Cut Pro. In order to bring the shots into After Effects, I exported a Quicktime reference movie out of FCP (in order to maintain correct in and out points) and then brought that clip into After Effects.

Here is where the problem begins.

In order to keep the correct aspect ration and frame rate, I had been interpreting the QT footage with these After Effects specs:


CONFORM TO FRAME RATE: 29.97
SEPARATE FIELDS : LOWER FIELDS FIRST
REMOVE PULLDOWN: OFF
PIXEL ASPECT RATIO: D1/DV NTSC WIDESCREEN 1.2

These specs served me well, but brought down the image quality slightly. Other than the image quality loss, the interlacing and frame rate worked in conjunction with our FCP timeline and our raw footage, The only times we ran into any problems was when we did a time-ramp or slow-down in both FCP and After Effects. When we applied any kind of time-adjustment, the entire frame jittered up and down, being most obvious in the widescreen bars. As a temporary fix, I had been blowing up the image slightly and masking off a new widescreen bar. This works well enough, but the loss of quality from a blow-up is undesirable.

I decided to experiment more with my interpret footage settings. On a shot in which I was doing an After Effects slo-down, I tried to set my REMOVE PULLDOWN to SSWWW.
I was surprised to see a crystal clear image with no jitter or noticeable de-interlaced frames. I looked through my After Effects timeline at previous shots that were referencing the same Quicktime media and saw a noticeable increase in image quality. Lines and pixels were clear and less blurry and grainy, as they had been using the previous INTERPRET FOOTAGE settings.

So, thinking I had found the solution to all of my FCP/After Effects problems, I went into another scene and applied the same settings to that Quicktime reference movie. This is where things got strange.

From this QT reference movie, I had about 10 effects shots that were referencing it. Of those 10, half of them looked great from this SSWWW pulldown change, but the other half resulted in clear pictures – but distracting deinterlaced frames, where the upper and lower fields were de-registered. This doesn’t make any sense to me because these shots were all shot using the same DVX settings, and uploaded into FCP using the same import settings.

We’re just about wrapping this movie up and I’m desperate to get a correct answer for this. I’ve talked to a few people who had recommended the initial settings I used, but after seeing the image quality improvement that the SSWWW pulldown settings SOMETIMES gave me, I’m hesitant to go any further before figuring this out.

Has anyone here run onto any similar situations? Does anyone know why only some of the shots would be plagued with these nasty video interlace artifacts? I would appreciate any kind of response!

Thanks,
Eric Manche
 
Sorry I don't have an answer to your question, but I have been using AE for quite a while now and don't understand working interlaced in AE fully. If you interpret as lower fields, you still have your duplicated fields at 29.97 (since you shot 24), but the ripped fields go away. If you import an interlaced image sequence, you will see tearing. When you interpret as lower and render back out, you'll see that tearing is gone from your output as well. AE isn't deinterlacing I don't think, but I can't figure out how the interpretation works.

Similarly, guessing 3:2 pulldown will pick cadences that are inconsistent for each clip even though the clips are from the same camera. I usually go to the first torn frame and then guess 3:2 in the interpret footage dialogue, but it's still somewhat mysterious. I wonder if your quality improvement with 3:2 instead of interpreting 29.97 lower is due to some sort of field blending algorithm AE applies when you interpret to make it look nice on your RGB screen? Sorry I can't be of more help, but I'm curious to see if anyone knows anything...
 
Hi Eric.
I was a longtime reader once...Ooh those days.

Anyways.
Why did you interp the footage?
Are using stockfootage explotions?
You shoot 24p,edit 24p and the vfx you do in 29.97i (60i)?WHy not leave it 24p?IS your output going to be broadcast?
No wonder your footage looks jerky when you do time strechting and stuff.
IF you leave it @24p all should be fine.
 
Hey Eric,

Try different pulldown cadences. Instead of SSWWW, try some of the other ones. I once did a commercial a while back that was shot at 24p on a Varicam, and the footage was downconverted and transferred to DigiBeta and I had to try several different cadences before I found one that worked. Oddly enough, several of the shots worked better with several different cadences, so try playing with those and see what happens.
 
Hey guys,
Thanks for the responses...
to Cannes, yes - I ended up eventually trying out all of the cadences, and for whatever reason different shots require different interpretation settings. There doesn't seem to be any kind of logic to it, but it works great so I just have to experiment with these settings for every shot.
Everts - yes, they were stock explosions... sometimes, sometimes animated. The 24p Non-advanced is actually 29.97 in editing time-bases so the footage has always been 29.97.
Thanks for the answers! I'll be posting a link to the final project when all is said and done. There's an old effects demo reel from the project online, but most of the effects have been overhauled.
http://www.ericmanche.com/demo2008.html
Thanks again!
Eric
 
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