I want part of my video to be visible and the rest masked out using a rectangular matte. Garbage matte or track matte are obvious choices. Now comes the difficult part: I want to animate the video's position or scale without the matte being affected by this.
Let's say my matte hides the right half of the video. Then I add some key frames to move the video 400 pixels to the left. What I see happening in PrE is that the track matte moves with the video, i.e. no new content is revealed by that movement.
In Photoshop I would click the little chain icon next to the layer mask to unlink the two. How can I achieve this with PrE ?
Unfortunately, that is a limitation of the Track Matte.
One workaround would be to create a Project, just for the material that you will be animating, and do the Keyframing there - nothing else on the Timeline. Then, Export/Share that Timeline, to be Imported and then limited with the Track Matte Keying in the main Project.
You might want to create a "guide" to see the "window," that will be provided by the Track Matte, when doing the initial animation. For more info, see this ARTICLE.
The choice of that Export/Share format will depend on what you are working with. I like using one of the Lossless CODEC's (which handles either SD, or HD material), like Lagarith Lossless, or UT Lossless. There is more info in this ARTICLE. For SD material, DV-AVI is a good choice too. While it is lossey, the compression is only about 5%, and for just one generation, will never be noticed.
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