User`s guide

Chapter 9 Motion Tracking
494
Using Motion Tracker Data in a Filter Track
You can follow a moving point in a file. This technique is useful when using a filter that has
position controls, (for example, Spotlight, Bulge, or Ripple). For example, you could track a
logo on a t-shirt and then use the Mosaic filter to make the logo unrecognizable.
You can also use this technique in filters that have a PixelChooser tab, since the
PixelChooser contains position controls. This allows you to selectively filter a specific area
in a moving image, like a face or logo to blur.
For a list of filters that can be used with the Motion Tracker and parameters in each filter to
which tracker data can be applied, see “Apply Tab (Motion Tracker)” on page 507.
To use Motion Tracker in a filter track:
1. Create a shape track containing the file you want to track. This can be a movie file, a
host video track, or an animated still image file. Name this track Track 1.
2. Apply the filter that you want to follow Track 1 directly to the timeline. Make sure that
the filter track is above Track 1 in the timeline.
3. Apply the Motion Tracker filter to timeline. Drag the Motion Tracker into the filter track
created in Step 2. Ordinarily, you cannot apply one filter to another filter in Avid FX, but
you can apply the Motion filters to other filter tracks.
4. Expand the Motion Tracker track to reveal the Source track. Assign the Track 1 media to
the Source track. You may want to create a duplicate of Track 1 and drag it into the
Source track.
5. The Motion filters support Start Time, Clip Head and Clip Tail parameters which are set
in the Source track’s Media tab. The analysis starts at the Clip Head and ends at the Clip
Tail or the last frame of the effect, whichever is shorter. If you don’t want the filter to
apply to the entire track, set a new Clip Head and Tail—see “Importing Movie Files” on
page 143.
6. Generate tracker data. For information on this process—see “Analyzing Motion” on
page 496.
7. If necessary, you can manually correct any errors in the generated data—see “Manually
Correcting Errors” on page 497.
8. Select the Motion Tracker track in the timeline. In the Controls window, select the
Apply tab. The Apply Tracker Data To menu updates automatically to display
parameters that can be affected by tracker data. The choices vary depending on the filter
you are using. Select the appropriate choice.
The filter now follows the motion in Track 1. You can still animate or otherwise adjust the
filter track and/or the Source track without affecting the Motion Tracker.