The following is a brief discription of VideoPoind that appears on page 7 of the "VideoPoind User’s Guide".

VideoPoint software in a Nutshell

VideoPoint is designed to help you analyze the motion of features or objects of interest in digital video movies. This software will allow you to define characteristics of a series of points you would like to examine on each frame. These characteristics include the name, the size and shape of the marker,, the mass,, and the coordinate system each point series is associated with. You will also be able to specify the length of objects or distances between features in frames for scaling purposes. In addition to obtaining data via the selection of features or objects of interest on frames, you will be able to define calculated data points such as the location of the center of mass of a system of features or objects. Data that are obtained can be graphed as they are located or calculated. Data can be saved in an electronic file or copied for use with other types of analysis software such as spreadsheets and graphing programs. VideoPoint runs on both the Windows and Macintosh platforms.

The complete manual is on the VideoPoind CD in the USER_GDE directory. It is in both the PS and the QUARK subdirectories of the USER_EDE directory. It is in both Postscript and Quark format. Readers for thest formats are available on the internet as freeware or shareware.

There are hints for use of VideoPoint, a discussion of its features, a section on tips and tricks for VideoPoint, a step-by-step example and a FAQ section on web sight "http://lsw.com/videopoind/ ". This step-by-step example is also available on the VideoPoint CD in the walkthru directory the startup file is Index.htm and can be accessed through an internet browser or by executing the example program when VideoPoint is installed.

The following is Chapter 2 from the VideoPoint version 2.0. This chapter includes sections on the instillation and use of the software.

2.1. How to Install the Software

System Requirements

Versions of VideoPoint are available for use with either Macintosh computers operating under System 7.x or PC’s with Windows 3.1 or Windows95. Both versions are included on the CD. No special hardware is needed when VideoPoint is used to analyze digital movies in the QuickTime format. However, if you wish to create your own digital movies for analysis, you will need to add an additional digitizing card that can capture video information in a QuickTime format. A capture card can have a video camera, VCR or Videodisk player attached to it. For more details consult Chapter 6 on "Creating Digital Movies for Analysis."

Macintosh Requirements

VideoPoint requires a QuickTime compatible computer (LC or later) running System 7.x or later, QuickTime 2.0 or later (QT 2.5 is included on the CD),

2.5 MB of free RAM, 3 MB storage space on your hard drive, and a CD drive

for installation.

Windows Requirements

VideoPoint requires Windows 3.1 or Windows95 with QuickTime (included on the CD), 8 MB RAM, 3 MB storage space on your hard drive and a CD drive for installation.

Installation

Installing the Video Point Software and QuickTime—To install VideoPoint and QuickTime, open the MAC folder on the CD and double click on "VideoPoint 2.0 Installer" This will give you the option of installing VideoPoint and QuickTime or just VideoPoint (for machines that already have the latest QuickTime installed). The Movie Browser can run off the CD directly.

If you do not own a CD drive, you should install VideoPoint onto a machine that does have a CD drive, then copy the VideoPoint program as well as the QuickTime extension(s) in located in the Extensions Folder into the Extensions folder of the machine without the CD drive.

Note that the installer gives you an option to install VideoPoint without curve fitting. Some people want to keep their students from using the curve fitting until they fully understand how to model data. These instructors can install without curve fitting first, then replace it with the curve fitting version later.

Installing the Movie Browser--- The Movie Browser can run off the CD itself. You will probably want to make an alias to the browser and put it on your local machine.

Installing Video Point Software and QuickTime— In either the Program Manager or the File Manager, choose File->Run and type "e:\SETUP" where "e" is the letter of the CD drive. Follow the instructions to install VideoPoint. This will install both the VideoPoint program (vidpoint.exe) and QuickTime for Windows. It will also create a program group in Windows 3.1 or place it in the Start menu in Windows95.

Note that the installer gives you an option to install VideoPoint without curve fitting. Some people want to keep their students from using the curve fitting until they fully understand how to model data. These teachers can install without curve fitting first, then replace it with the curve fitting version later.

Installing the Movie Browser— The Movie Browser can run off the CD itself. A icon will be placed in the Program Manager group.

2.2. A Typical Analysis

The easiest type of movie to analyze is a movie with a single feature of interest that was taken with a camera that does not move or zoom during filming. Let’s start by analyzing a ball launched from a fixed table.

Opening VideoPoint

MAC- Double click on the icon in the finder.WIN- Double click on the Program Item in the VideoPoint group.

A Sample Analysis

Setup Screens

Once VideoPoint is opened the following setup screen will appear. To start, click on "Open Movie..." to open the movie you want to analyze. To work with this example, you should choose the movie entitled "PRJCTILE.MOV" located in the examples directory. Figure 2-1: The Videopoint startup screen.

A screen showing the first frame of the movie should appear. You will be invited to enter the number of features or objects that you want to locate on each frame. Since only one ball is launched during this movie, type 1 into the box and hit "OK."

Figure 2-2: The second screen which allows you to indicate the number of features or objects of interest to be located on each frame of the movie.

The movie should appear along with a Coordinate Systems Window. Initially the Coordinate Systems Window shows two Cartesian systems; the "Origin 1" coordinate system and the "Video Origin" coordinate system. A single video point series (the one specified in the previous dialog box) called "Point s1" has been placed in the "Origin 1" coordinate system; "Point s1" will report all its data relative to the "Origin 1" coordinate system.

Figure 2-3: The default working screen showing the movie and coordinate systems windows.

Playing the Movie

Play the movie by clicking on the play button on the movie controller which is located at the bottom of the screen.

Rewind the movie by either dragging the slider on the movie controller back to the beginning of the controller or by choosing "Movie->Rewind" (Ctrl-R).

MAC users: Use Command-R instead of Ctrl-R

Taking Data

To make locating the points easier, you can increase the size of the movie by either choosing Movie->Double Size or by hitting the keyboard shortcuts of Command-2 (MAC) or F7 (WIN). If you are using a small monitor, you may want to use Movie- >Fill Screen or its shortcuts Command-3 (MAC) or F8 (WIN).

Move the cursor over the movie window area. The cursor should look like this, and the bottom right of the movie window should have the italicized text "Point s1." This is the first video point to be located by you in the frame that currently appears in the movie window.

Be sure to click in the very center of the ball on each frame. The more precise you are in the data collection step, the better your data will be for analysis.

Cursors in the Movie Window

If the cursor looks like this, clicking on the movie window will locate the video point that is currently selected.

If the cursor looks like this, you can select a previously located video point and use a drag and drop technique to move it to another location.

Move the cursor so that the ball being launched out of the projectile launcher is centered in the cursor. Click once to locate this video point.

The movie will automatically advance to the next frame. Continue clicking on the location of the ball in each frame until the last frame of the movie.

You have now collected data for this movie. However, the data are still in pixels since you have not yet scaled the movie.

Scaling the Movie

This process tells VideoPoint how many screen units (pixels) in the Movie Window are in a meter, a centimeter or a millimeter in the actual scene. Conveniently, a 1.00 meter long meter stick was placed in"PRJCTILE.MOV"; this will be used to scale the movie.

Starting the Scaling Process

Click on the scale icon in the toolbar. The following dialog box will appear.

Figure 2-4: The Scale Movie Dialog Box.

The length of the scale object (in this case, the meter stick) is known to be 1.00 meter. Enter this value into the "Known Length" box. Since we want to scale the coordinate system relative to "Origin 1," select "Origin 1" in the "Scale Origin" pop-up menu. Since the camera did not zoom at the instant when the movie was taken, choose a "Fixed" scale type.

Once these values have been set, you are ready to begin the scaling process:

1. Click on "Continue."

2. Click once on one end of the meter stick.

3. Click once on the other end of the meter stick.

Note that three new rows appear on the Coordinate Systems Window. Two rows, Scale1 A and Scale1 B, specify the ends of the object that you clicked on. The third line, called Scale1, stores the ratio of the length of the object relative to the distance between Scale1 A and Scale1 B.

You have now scaled this coordinate system by telling VideoPoint that 1.00 meter is equivalent to the distance (in pixels) between the two video points that you just clicked on.

What are the Scale1 A and Scale1 B video points?

These two video points are used by the program to determine the number of pixels between the ends of an object or the distance between two features used for scaling on a video frame. If the actual distance (in meters, centimeters or millimeters) between the Scale1 A and Scale1 B video points is known, then a scale factor can be determined for the frame. This scale factor is calculated as the ratio between the number of pixels between Scale1 A and Scale1 B and the actual distance between these points specified by you. Moving either of the two scaling video points closer together will decrease the scale factor and moving them farther apart will increase the scale factor.

Graphing Data

Set your movie back to a normal size by choosing Movie>Normal Size or

typing the keyboard shortcuts of Command-1 (MAC) or F6 (WIN). To graph the data that you have collected, click on the graph icon in the toolbar or choose View->New Graph (Ctrl-G) from the menu bar. The following dialog box will appear.

Figure 2-5: The Plot Series dialog.

Leave the horizontal axis at its default setting of "Time". For the vertical axis, choose "Point S1" and "y" from the two pop-up menus, and then select position and velocity from the list. You can select multiple items by simply clicking on them. Clicking on a selected item in the list deselects it.

This will plot both position vs. time and velocity vs. time in the same window on two separate graphs. The plot should look something like this:

Figure 2-6: A Graph window showing a plot of Point s1:Y (m) vs.

Time (s) for a projectile.

Repeat the graph process for an X vs. Time plot for Point s1.

Creating a Mathematical Model of the Data

Since many of the motions of interest in the study of physics can be described by analytic functions, VideoPoint has a graphical modeling feature that enables you to try to develop a mathematical model for a motion. You can do this by comparing a graph of the motion to a graph of an equation. For example, in analyzing a movie of a bungee jumper in free fall, you could select a graph of the experimentally determined values of y vs. t. Then you could choose to model the data with a quadratic equation and then match the parabolic line to the data by changing values of the equation coefficients. Is the coefficient of the t2 term close to -4.9 m/s2?

Figure 2-7: Model of y vs. time for the ball toss. Note that this is a model

and not a fit. To complete a model efficiently a user must understand how

to recognize the type of function that is needed and how each of the equation

parameters affects the mathematical function. Note the Model equation dialog box that follows.

How to Create a Mathematical Model

To model y vs. time for this projectile in Figure 2.6, click on the graph to bring it to the front. The time labels should move up to rest just underneath the position vs. time plot. Then choose Graph->Add/Edit Model or click on the  icon on the edge of that graph.

Figure 2-8: The Modeling Dialog Box

Since Y vs. Time is a parabola for this projectile, choose the "Quadratic" formula. Enter appropriate values in each box that correspond to the constants in the equation. Click on "Apply" to view your modeled graph (shown as a green line) without closing the dialog box. Once you are satisfied with your model, click OK to close the dialog box.

If you entered A:= 4.94, B:=3.00 and C:= 0.368 , your model should like this:

Figure 2-9: A Graph Window showing data points and the line which is a graphical representation of a mathematical model of the data.

The constant A (for the x2 term) should be approximately -4.9 since this is a projectile that can be modeled by the equation y = 1 /2 gt² + v_ot + y_o.

Creating a Fit of the Data

Alternatively, you can fit the data automatically. If you installed without the curve fitting, you can move on to the next section. To fit the velocity versus time data, click once on the velocity plot (the time labels should move back down to the bottom of the window) and then choose Graph->Add/Edit Fit or click on the  icon. The following dialog should appear.

Figure 2-10: Curve fitting dialog.

Leave the "type of Fit" to "Linear". If you want VideoPoint to update the fit every time that you move a point on the movie, click the "Update Automatically" box, otherwise, you can update the file by opening this dialog and choosing "OK" or "Apply" later. For this example, check the box and click on "OK".

The fit of the velocity plot should appear and look something like this:

Figure 2-11: Fit of y component of velocity vs. time.

As you might expect, the slope of this line should be approximately -9.8, since this can be modeled by the

equation v = v_o + at.

Relating the Graphs to the Movie

One of the great features of video analysis is the ability to replay the situation. Bring the movie window to the front by clicking on it. Play the movie by clicking on the play button.

Watch the graphs while the movie plays. A circle should move along the graph points indicating the current time of the movie on the graph.

Play the movie or pass through the frames by using the slider bar.

Live Updating

One of the coolest additions in version 2 is the ability to watch the graphs update while you move points around on the movie.

Advance the movie to about the middle using the step buttons  . Click and drag the "Point S1" marker. Watch the graph window update simultaneously. Note the sensitivity of the velocity plot to the location of the point.

Figure 2-12: Dragging a point on the movie updates it on the graphs automatically.

Viewing the Data in a Table

If you want to view the data that you have taken, click on the table window icon or choose View->Data Table. You can select and copy any portion of the data; clicking on the (x) and (y) headers will select entire columns.

Figure 2-13: The Table Window showing the coordinate data of Point Series 1 in Cartesian coordinates.

Saving Your Work

Choose File->Save. Decide where you want to save your file.

What Information is Saved with a File?

The file contains all your data and open windows as well as the name and location of th movie file. It does NOT contain or change the movie file. This keeps the file sizes small and allows files to be associated with movies that are stored on "read-only" networks.

You have successfully analyzed a movie with VideoPoint. Congratulations.

You can consult the VideoPoint User’s Guide to learn how to analyze movies for which you would like to define more than one video point series or use different coordinate systems. The User’s Guide also contains information about how to deal with movies taken with a moving or zooming camera.