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Corner Pin with Scaling into layer

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Chris Arnold
Corner Pin with Scaling into layer
on Feb 4, 2010 at 10:34:04 pm

I am doing a screen replacement on a laptop computer. The shot was tracked in Mocha and corner pin data brought into After Effects. Next up I am animating the scale of both the video and the corner pin layer together so that the camera pushes fully into the screen.

Now when I push into the computer, the computer starting a mid distance away, the replaced video (layer with corner pin data) gets extremely pixelated because of the nature of the effect. The corner pin effect stretches the layer small to fit the screen and when it gets scaled up it doesn't have the resolution to play with anymore.

Any Ideas how to make this work so I end with a high resolution screen?

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Dave LaRonde
Re: Corner Pin with Scaling into layer
on Feb 4, 2010 at 11:21:36 pm

[Chris Arnold] "Any Ideas how to make this work so I end with a high resolution screen?"

I presume you're working with something like HD in and SD comp; otherwise, your computer screen is going to get pretty darned ugly-looking as you scale it up.

If that's the case, simply change the order in which you do things: scale up the shot in its own comp, render it, and then track with Mocha.

If you're trying to scale up a shot beyond 100%, you should read this:

Dave's Stock Answer #2:

When you're out on a shoot, and you say, "we'll fix this in post" without knowing PRECISELY HOW you're going to fix it in post, don't shoot it! You'll only end up shooting it over again.

Since post typically costs three times the cost of production, fixing something in post is not a way to save money, but rather a way to spend more of it.

And, before you say "well fix it in post," always consider who's doing the work, especially if you're the one doing the work.

.... and if the shot you're scaling up is on HDV, you should read this:

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, 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.

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

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Chris Arnold
Re: Corner Pin with Scaling into layer
on Feb 6, 2010 at 1:44:56 am

Thanks for the tip. I'm Mastering at HD (1080p). I tried the technique and found out from the camera zoom in I would need about 3 times the resolution, so I sent a scaled up video file (5760 x 3240) to Mocha and then used that corner pin data on a solid of the same size. Then scaling the footage down by 33.33 % to match the 1080p footage it had just the right resolution for the camera zoom in.

The only thing with this method... tracking footage that size can be a real time killer.

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