Videos

1. Opening a Video File

To open a video into a new tab, use the Open button or File|Open menu item. To import a video into an existing tab, use the Video|Import, Video|Replace or File|Import menu item.

In the file chooser, set the file type to Video Files and select the desired file. Tracker will open JPEG images and animated GIFs as well as QuickTime movies and AVI files.

Note: If Tracker cannot open a movie file, you may need to reinstall QuickTime. Tracker does not support MPEG files at this time.

2. Pasting Images from the Clipboard

Images that have been copied to the clipboard may be pasted directly into Tracker for analysis. Choose the Video|Paste Image menu item to create a new video. If an image video is already open, you can paste or import additional images using the Video|Paste Image or Video|Import Image menu choices. You can also remove images from image videos using the Video|Remove This Frame item.

3. Setting Video Clip Properties

A video clip is a subset of frames in a video defined by a start frame, step size (number of frames per step), and end frame. The start frame is the frame number of the first step, the step size is the frame increment between successive steps, and the end frame is the frame number of the last step. For example, a clip with start frame 3, step size 2 and end frame 11 would have step numbers 0, 1, 2, 3 and 4 that map to video frame numbers 3, 5, 7, 9 and 11, respectively.

A clip is defined for every video and even for no video. For single-frame and null videos the clip settings apply to tracks but every step maps to the same video image.

Video clip properties are set in the clip inspector. To display the clip inspector, click the inspector button at the right end of the player.

The clip inspector shows thumbnail images of the start and end frames along with the current video clip settings. In addition, there are fields for setting a start time (time assigned to set 0), the time interval dt between steps (important for high-speed or time-lapse videos) and the play rate as a percent of normal playback speed.

Note: since point mass tracks require that you mark their steps for every frame in the clip, it is most efficient to define the clip before marking. Clip properties may be changed at any time, but previously unmarked frames will then require marking.

4. Using the Video Player

The player includes (from left to right):

- time/step readout
- play/pause button
- slider
- step forward button
- step back button
- loop button
- clip inspector button.

You can drag the entire player by the left end to convert it to a floating window if desired.

Click the Play/Pause button to play the video at the rate specified in the clip inspector; click again to pause the video. Drag the slider to scan a video or move quickly to a desired frame.

Click the readout to choose Frame (number, measured from the beginning of the video), Time (seconds, measured from the start frame) or Step (number, measured from the start frame). The readout displays frame number by default.

Click the Loop button to toggle looping (continuous play).

5. Magnifying (Zooming) a Video

Magnify the video image up to 8x by right-clicking on a point of interest in the main video view and choosing the desired zoom level. The right-click point will stay near the center of the magnified view.

Zooming To Fit forces the video image to always fit the main video view.

6. Applying Filters to a Video

Video filters allow you to modify the video image. Create a new filter with the Video|Filters|New menu.

Set a filter's properties in its properties dialog. The dialog pops up when the filter is created and remains accessible from the Video/Filters menu.

Multiple filters are applied in the order in which they are created and listed in the Video|Filters menu. Existing filters can be temporarily disabled or permanently deleted. Choose Video|Filters|Clear to delete all filters.

Note: Some filters produce an effect that is seen only with moving objects. A ghost filter, for example, leaves a trail of fading ghost images of a moving bright object.

7. Hiding and Closing a Video

Uncheck the Video|Visible menu item to hide the video image and display the tracks on a white background. Choose Video|Close to remove the video permanently.

Note: when removing or replacing a video, a new video clip is created. This may result in some tracks having existing steps that are no longer included or unmarked steps that are newly included in the clip. If this happens, correct the problem by resetting the start frame, step size and step count for the new clip.

8. Recording a Video

Tracker can record the current video clip with filters and visible track overlays as a QuickTime movie or animated gif. The movie or gif will have the dimensions of the current viewport in the main video view.

Note: QuickTime movie file sizes can be large since they are not currently compressed! Animated gif files are always compressed, but have only 256 colors.

To record a video, select the File/Record menu item. This will bring up the Video Capture Tool which allows you to control the frame capture process and preview the video before saving it.

Note that the video dimensions are those of the main view. To produce a smaller video, shrink the main view window and set the Zoom level "To Fit" before starting the recording process.