Track matte key. Am I doing something wrong?

Question

Hello everyone. I'd appreciate it if you could help me on the following: On a Premiere sequence, I have 3 video tracks. Tracks Video 1 and Video 2 contain 2 separate clips and track Video 3 contains a jpg static video matte (black and white). What I need to do is I want to use the jpg image as matte, so all I do is place the three assets on top of each other and then apply a track matte to Video 2, set its matte to Video 3, set compositing to luma and bingo! My 2 videos on track 1 and 2 are now playing with the mask I set to them.

Now say I want to scale up in my clip in video track 2, so that I focus on a different part of it, but with the mask applied and not changed at all. What I found out is that no matter whether I scale the clip before or after I apply the track matte key, the result is applied on both the mask AND the clip. Why does this happen? Is it a version bug or do I get something wrong? Shouldn't the clip scale be able to get carried out independently of the applied track matte? And why is this procedure carried out as it should be on After Effects but not in Premiere?

To get a better idea of what I mean, I uploaded a video on YouTube, regarding the issue. As you'll see, to get the exact matte size from one clip change to another, i had to split the mask jpg using the razor and then apply a different scale on it. What would be the case if I had, say, 20 different tracks?

The clip is located here http://youtu.be/da52U9ZfLAw

Thanks in advance

Steven L. Gotz · Accepted Answer

Motion and track mattes do not mix. You need to do the motion in a nested sequence.

Take the track matte and the video that you are applying motion to into a new sequence. Set the matte on top and set the opacity to 50%. Use motion on the video just the way you want it. Then poke out the eyeball on the matte's track so you don't see it.

Now you can nest that sequence into the main sequence and apply the track matte to it instead of the original clip. Since Premiere Pro does not see the motion in the main sequence (it is actually happening in the nested sequence) then it does not bother the track matte effect.

Anonymous · Answer

I'd like to clarify a bit on this: you're facing two issues there:

- render order;

- bugs in the Track Matte Key effect.

Regard to the first one, all effects are rendered in a particular order:

- from top to bottom according to their position in a list of applied effects;

- Fixed effects are rendered after Standard effects;

- nested content is rendered in ascending bubble mode: from a greatest depth to a surface.

Therefore, so as to trick the render order you can e.g. instead of manipulating the Motion effect's properties apply the Transform effect prior to any other Standard effects or nest your footage and manipulate the Motion effect's properties inside the nested sequence.

Regard to the Track Matte Key bugs, you can't sometimes trick it with the Transform effect and, hence, as Steven said, have to nest.

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