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Defining tracking settings (PB only)


    Use the Options dialog box, available from the Tracker/Stabilizer Controls, to specify the second layer or the effect, and to define other tracking settings. The controls are as follows:

    Layer menu

    Specifies the layer you want to attach to the tracked layer.

    Effect Point Control menu

    Specifies an effect to attach to the track point. Note that you can attach only those effects that have position properties.

    Frames per Second

    Specifies a frame rate for tracking. In general, the tracking frame rate should match the frame rate of the footage, which should match the composition's frame rate.

    Tip iconIf you are attaching a motion graphic to the tracked area, be sure to match the frame rates of the two layers.

    Track Fields

    Tracks the motion in both video fields of interlaced video. The Track Fields option doubles the frame rate to ensure that both video fields are tracked.

    Track in Reverse

    Tracks backward in time. For example, if you are tracking an object that comes in from off-screen, you can define your tracking regions at the end of the clip and then track backward in time.

    Use

    Specifies the type of comparison method to use for tracking an object in subsequent frames. RGB bases tracking on all three color channels. Luminance compares the contrast in brightness values in the tracking region. Saturation looks at how much color is present in the tracking region.

    Process Before Match

    Blurs or sharpens an image to enhance the search capabilities. Select Blur to specify the number of pixels that the Tracker/Stabilizer blurs before processing a match. Blurring temporarily reduces noise in the footage to help produce better tracks.

    Note that blurring occurs only for the purpose of tracking. The footage is restored to its original clarity after tracking. Usually a value of 2 to 3 pixels can help produce better tracks, especially on grainy or noisy footage. Enhance exaggerates the edges of an image to make them easier to track.

    Track Adaptiveness

    Controls how much of the original frame and the following frame are used for matching. A value of 100% means that the Tracker/Stabilizer updates the feature information from one frame to the next, based on the location of the feature region. A value of 0% means that the Tracker/Stabilizer uses feature information from only the original image when matching each subsequent frame. Use larger values if your feature changes shape, color, or brightness during the tracked frames. Use smaller values if the feature doesn't vary across the tracked frames or if subpixel drifting is a problem.

    Extrapolate Motion if Accuracy is Below _%

    Specifies a tolerance level that determines when the Tracker/Stabilizer extrapolates the motion of hidden objects. If the accuracy percentage falls below the specified tolerance, the Tracker/Stabilizer extrapolates the position of the feature region while it is obscured by another object. For example, if you track a dog that walks behind a person, the Tracker/Stabilizer can estimate the position of the dog in those frames where it is obscured.

    Subpixel Matching

    Divides each pixel in the feature region into smaller divisions. The Tracker/Stabilizer tracks a selected feature region by matching pixels and fractions of pixels from one frame to the next. The smaller the fraction, the more accurately the Tracker/Stabilizer tracks the selected region. Depending on the size of the feature region, however, selecting a small pixel fraction can significantly increase the tracking time.

    Save button

    Saves a data file that contains the currently selected options, positions for the feature region, search region, and track point, and any tracked areas for the layer.

    Load button

    Loads a saved tracking data file.