The Analyze Motion behavior analyzes and stores tracking data from a video clip or image sequence, but does not transform the tracked footage. Analyze Motion data tracks are meant to be referenced by the Match Move, Stabilize, Track Parameter, and Track Shape behaviors. For more information, see Analyze the motion of a clip.
After you apply an Analyze Motion behavior to a clip, the Behaviors Inspector displays the following adjustable controls:
Movement: Two controls used for the motion-tracking analysis.
Analyze: A button to activate a motion-tracking analysis. When you click Analyze, a status window appears and displays the tracking progress. To stop the analysis, click the Stop button in the status window or press Esc.
The start frame of the track analysis is based on the current playhead position, rather than the beginning of the behavior bar in the Timeline.
Reverse: A checkbox that, when selected, reverses the analysis direction, going from the playhead position to the first frame of the clip (or the first frame of the tracking behavior).
Note: You must move the playhead to the frame where you want the reverse analysis to begin.
Tracker: A button to add onscreen trackers to the Analyze Motion behavior. By default, one tracker is available. New trackers are added at the center of the Canvas.
Tracker Preview: A preview providing a magnified view of the tracking reference area for a selected tracker. The preview updates as you adjust the position of the tracker in the Canvas. You can drag in the preview area to adjust the position of the tracker. When you do so, the image in the preview area moves around the red crosshair representing the tracker, and the tracker moves in the Canvas. You can also Option-drag left or right in the preview area to decrease or increase the size reference pattern to be analyzed in the Canvas. (Alternatively, you can adjust the Track Size slider, described below, to achieve the same result.)
Offset Track: A checkbox that, when selected, lets you set a new tracker position when the original reference pattern becomes temporarily obstructed by an obstacle, or goes off the screen. Motion uses the tracker position to continue the same tracking path begun by the original reference pattern. For more information on offset tracking, see Track obscured or off-frame points.
Auto-Zoom: A pop-up menu to choose a magnification level when positioning the tracker in the Canvas. You can zoom in on the Canvas when searching for an ideal tracking reference pattern. There are four choices: None, 2x, 4x, and 8x.
Auto-Zoom Mode: A pop-up menu to set the display of the auto-zoomed tracker in the Canvas. There are three choices:
Normal: Displays a normal pattern.
Contrast: Displays the tracker pattern with contrast detection.
Edge: Displays the tracker pattern with edge detection.
The Auto-Zoom Mode applies to trackers in the Canvas and does not appear in the Tracker Preview in the Behaviors Inspector.
Note: When Auto-Zoom is set to None, the Auto-Zoom Mode setting has no effect.
Look Ahead Frames: A slider and value slider to specify the number of future frames to be analyzed by the tracker. In other words, you can direct the tracker to look in a specific location for its reference point, which helps the tracker follow fast-moving objects. For more information about the Look Ahead Frames control, see Advanced strategies to improve tracking results.
Track list: A list displaying the trackers in the behavior (Track 1, Track 2, and so on). To disable a tracker, deselect its checkbox. To remove a tracker, click its adjacent Remove button. A tracker that is turned off is not analyzed. Click the disclosure triangle next to the track name to reveal additional subparameters:
Position: Value sliders displaying the X and Y positions of the tracker.
Track Size: A slider to set (in pixels) the pattern search size for the tracker. As you adjust the tracker size, the Tracker Preview is updated to show the new pattern search size. However, there’s no visual change in the Canvas tracker. (In a traditional tracker, Track Size would be the pattern searched within the inner tracker box and the outer tracker box.)
Alternatively, you can adjust the Track Size parameter by Option-dragging left or right in the Tracker Preview area.
Search Size: A slider to set search area size for the tracker. In Motion, you do not specify the size of a search area when setting up trackers in the Canvas. If your clip contains a lot of rapid movement, for example, you may have better results increasing the Search Size. For example, if Search Size is set to 150%, the tracker searches 50% further beyond the Track Size setting.
Fail Tolerance: A slider to set the amount of tolerance for error, or confidence value, of the tracker. In other words, Fail Tolerance defines a threshold score at which the tracker determines it can match a reference feature. When the analysis yields a score above the Fail Tolerance value, the tracker accepts the match. When the score is below the value, the tracker rejects the match.
Fail Behavior: A pop-up menu to specify what happens if the track confidence value falls below the Fail Tolerance amount. There are six menu options:
Smart Retry: The tracker attempts to find the reference pattern in a larger search area. If the pattern still cannot be found, the tracker switches to the Predict option (described below). Smart Retry is the default Fail Behavior setting.
Stop: The analysis stops when the tracker loses the reference pattern.
Predict: The tracker predicts a new search area without creating keyframes until it finds a match for the reference pattern. This option is excellent for tracked elements that pass behind foreground elements.
Predict and Key: If a failure is detected, the tracker predicts the location of the next track point (keyframe) based on a vector of the last two keyframes, and continues tracking in the new area.
Don’t Predict: The tracker remains in its position and searches for subsequent matches as the clip’s frames progress. While searching for a match, the tracker does not create keyframes.
Use Existing Keyframes: The tracker uses keyframes you have manually created as a guide. After manually adding keyframes, return to the start frame and start the tracking analysis. If the tracker has difficulty locating the reference pattern, the manually created tracking keyframes are referenced to guide the tracker.
Color: A color control to set a new color for the onscreen tracker. The default tracker color is red. When a tracker is selected, its center point is yellow and the border of its magnified inset is the color set in the color well. To adjust individual color channels, including the tracker’s opacity, click the disclosure triangle. For more information about color controls, see Basic color controls.