User Guide

CHAPTER 13

398

Using Property and Tracking Controls (PB only)

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.

UG.book Page 398 Wednesday, February 21, 2001 12:05 PM