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Interpret composition? (Not footage)

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Marc Brown
Interpret composition? (Not footage)
on May 5, 2010 at 9:03:03 pm

Subject says it all.

Here's my specific situation. I've got some film footage as a 29.97fps mpeg2. I want to be able to do some noise reduction on this footage. But I also plan to remove pulldown and get a 23.976fps video out of it.

After Effects lets me do both of these things. But I can't seem to do them in the right order. It lets me interpret the footage to remove pulldown. That works. And I can apply an adjustment layer to footage for noise removal purposes. But what it doesn't seem to want to let me do is interpret a composition.

In this case, I want to remove noise FIRST, and THEN remove pulldown. Why? Because removing pulldown complicates the noise by interlacing it at intervals, which in turn causes the noise removal to be both less than ideal and less than consistent.

And it is a mystery why I can't "interpret footage" on a composition, because there's nothing stopping me from, say, rendering my noise-reduced comp as RAW, and then interpreting THAT.

So am I missing something?


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Dave LaRonde
Re: Interpret composition? (Not footage)
on May 5, 2010 at 9:22:01 pm

[Marc Brown] "So am I missing something? "

Yup! Quite a bit, if I'm reading your post correctly....


[Marc Brown] " It lets me interpret the footage to remove pulldown."

When you remove the pulldown in AE, the footage becomes 23.976. And it needs to go into a 23.976 comp.



[Marc Brown] "Because removing pulldown complicates the noise by interlacing it at intervals, which in turn causes the noise removal to be both less than ideal and less than consistent."

Well, yeah, if you put 23.976 footage in a 29.97 comp, it gets all screwed up. But wait, there's more.....




[Marc Brown] "I've got some film footage as a 29.97fps mpeg2."

Aha! The ultimate culprit! Unless you've just installed the brand-new AE 10, you're going to have problems with that footage. Here's why:

Dave's Stock Answer #1:

If the footage you imported into AE is any kind of the following -- footage in an HDV acquisition codec, MPEG1, MPEG2, AVCHD, mp4, mts, m2t, H.261 or H.264 -- you need to convert it to a different codec.

These kinds of footage use temporal, or interframe compression. They have keyframes at regular intervals, containing complete frame information. However, the frames in between do NOT have complete information. Interframe codecs toss out duplicated information.

In order to maintain peak rendering efficiency, AE needs complete information for each and every frame. But because these kinds of footage contain only partial information, AE freaks out, resulting in a wide variety of problems.

-------------------------------------------------------------------

As a Mac guy, I'd convert it to a Quicktime movie in the Animation, PNG or ProRes 422 (if you have FCP6+) codecs, using Adobe Media Encoder, MPEG Streamclip (free download for either Mac or Win), Apple's Compressor or even QT Pro.


Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Marc Brown
Re: Interpret composition? (Not footage)
on May 5, 2010 at 9:45:03 pm

Okay. Actually, my old AE CS4 handles the mpeg2 footage quite well.

But if you're saying that the reason I can't interpret my 29.97fps comp as 23.976 with pulldown removal (the option is grayed out) is specifically because it contains interframe video, well, I suppose that's that.

Seems a bit odd, though. As I said, I do not experience any anomalies which would suggest AE is freaking out over the footage. I have even loaded the AE comp up into PPro, and even that kind of boat rocking hasn't generated problems.


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Dave LaRonde
Re: Interpret composition? (Not footage)
on May 5, 2010 at 10:11:30 pm

[Marc Brown] "I can't interpret my 29.97fps comp as 23.976 with pulldown removal (the option is grayed out)"

See? I thought I might be reading your first post improperly. I thought you were mixing 23.976 footage in 29.97 comp.

No. You can't interpret a comp like you can footage. To do what you want, you'll have to use a two-step process: remove the noise in one render, then reimport the footage and remove the pulldown to make 23.976 footage.

But that's a bunch of foolishness: just convert the footage, then remove pulldown and remove the noise as any sane person would.

I still don't understand how noisy 29.97 interlaced footage is easier to work with than noisy 23.976 footage. It makes no sense whatsoever.



[Marc Brown] "Actually, my old AE CS4 handles the mpeg2 footage quite well. "

To which I say the following: you've been lucky. And luck doesn't last forever.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Marc Brown
Re: Interpret composition? (Not footage)
on May 5, 2010 at 10:40:44 pm

Pretty simple, actually. The noise in question is largely of the mpeg2 mosquito and megapixel variety. These artifacts are of a consistent nature on their individual frames - ie the two fields of an interlaced frame, which are stored as two half-frames in one image.

Any kind of interlace-related modification to these frames (pulldown removal, for example) will chop these megapixels into an interlaced weave of artifacts. If a noise reduction effect is designed to work on whole frames (meaning both fields in a frame), it should be obvious why allowing such interlace manipulation prior to the noise reduction would complicate matters. Instead of working its magic on predictable noise, it has to deal with noise that has been woven together at the finest vertical level.

Perhaps this might help: Have you ever seen a video that was encoded while still being interlaced? It just doesn't work out too well. There are reasons.


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Dave LaRonde
Re: Interpret composition? (Not footage)
on May 5, 2010 at 10:54:39 pm

[Marc Brown] " Have you ever seen a video that was encoded while still being interlaced?"

Sure: every time I don't want to miss a football game, I set up the DVD recorder. Compressed. Interlaced.

Mpeg2 compression NEVER holds up to a critical eye.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Marc Brown
Re: Interpret composition? (Not footage)
on May 6, 2010 at 4:43:13 am

Nah, what I meant was, say, XviD or Divx compression on progressive video which happens to consist of interlaced frames - both fields already interwoven. The reason this gives a poor (and more importantly, less than ideal) result, as well as the fact that such a result is intuitable, is similar to the reason why noise reduction in my case is also less than ideal if done in the wrong order.

In my frank opinion, the "remove pulldown" feature in After Effects should have been something one could put on an adjustment layer, not a one-shot process that has to be done at a specific point in one's workflow. In terms of its ultimate purpose, it differs little from similar effects like Timewarp. The fact that I'm having to resort to the good ol' raw video to get my job done attests to the validity of this opinion.


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Dave LaRonde
Re: Interpret composition? (Not footage)
on May 6, 2010 at 3:30:39 pm

[Marc Brown] "The fact that I'm having to resort to the good ol' raw video to get my job done attests to the validity of this opinion. "

I say it attests to the fact that you're smoking the drapes or something. Are you trying to tell me that you actually PREFER working with footage whose quality has been compromised by encoding to a lossy codec as opposed to the same footage in its original state?

If that's true, you deserve the hassles you're going through, pal.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Marc Brown
Re: Interpret composition? (Not footage)
on May 7, 2010 at 1:04:19 am

No argument. If I had a raw 1080p file in front of me, I'd be rather happier. Unfortunately, what I do have is a DVD encode of a VHS tape.

Anyway, it looks a lot better now that I've gone through the considerable hassle of rendering off a 130GB raw file. I again question the wisdom of tucking pulldown removal away as a file interpretation rather than a temporal effect (or, ideally, both, so long as the need for raw renders is minimized).


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