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(Invisible) Buttons over Video in DVD Studio Pro

Using track buttons to add interactivity to a stream By Dave Nagel
It can be a tremendous pain to work with buttons over video when authoring a DVD. But, then again, they can be of tremendous benefit when you want to add interactivity to your presentation. They can do anything menu buttons can do but have the advantage of being active while a track is playing, so the viewer doesn't have to return to a menu to make navigation decisions. What's more, buttons over video don't have to be visible at all; users can interact with them via their remotes without ever knowing they're there. That means more creative freedom in your authoring projects.

There's any number of reasons you might want your viewers to be able to interact with your title via the numeric keypad on their remotes, although it isn't terribly common. You might have a "choose your own adventure" type of program where you want viewers to make choices while the track is running. You might want users to be able to switch to specific viewing angles directly. You might want to provide contextual navigation options without building tons of individual menus or scripts. Whatever. The possibilities are pretty much endless.

For this example, I'm going to set up a series of buttons over video that will be used for navigation. This is just an example to show you how to set up invisible buttons over video that activate automatically (without the need to hit Select after choosing a button) to perform a specific task. Using this example, you should be able to extrapolate whatever you need to add your own interactivity to your project using invisible buttons over video.

As it is, DVD players can access chapters through numeric keypad input from the viewer's remote control. But when buttons are active over video--even invisible ones--it's possible to override this functionality, so that when the viewer, for example, hits the number 4 on the keypad, he or she isn't taken to chapter 4 in the track, but, rather, taken to wherever button 4 points. And the button, of course, can point to anything a regular button can point to--an audio setting, a chapter in another track, a script, a slideshow, etc. And this is what I want to do. I want a number on the keypad to redirect the viewer to a particular chapter in a different track. So here's how that works.

Step 1: Creating a subtitle stream
Buttons over video operate within one or more subtitle streams, so you'll need to add such a stream to your track. To begin, you need to select the track to which you will apply your buttons. Double-click the track in the Outline tab to bring it up in the Track Editor.

Then, in the S1 slot in the Track Editor, right-click (or Control-click), and choose "Add Subtitle" or "Add Subtitle at Playhead." This will add a small, blank subtitle to your track.

Step 2: Button highlight marker
Now, in order to convert this subtitle stream into a stream capable of carrying interactive buttons, you must create a button highlight marker. This can be a new marker that you create at the point where you want the buttons to become active, or it can be an existing chapter marker that you use also as a button highlight marker. So create your new marker or select an existing chapter marker. Then, in the Inspector palette, click on the checkbox labeled "Button Highlight."

Note that if you do not want this marker to be a chapter marker, go ahead and deselect the checkbox for "Chapter Marker" in the Inspector palette.

Now that you've made this marker into a button highlight marker, you'll notice that your subtitle has expanded in duration to the end of your track, or to the next marker, depending on how you have your track set up. Buttons over video can never cross over marker boundaries, so, if you want the same set of buttons to be available over the entire stretch of your track, you'll need to create multiple instances of the buttons. We'll get to that later.

Step 3: Adding buttons
Now that your subtitle stream is prepared, you can add interactive buttons to it. To do this, double-click the subtitle stream. This will open up the Viewer window, and, by default, you'll be provided with a cursor for entering subtitle text. Click somewhere on the canvas to dismiss this cursor.

Now, to add your buttons, you create them in the same way as you would in a menu. In this case, since I want the buttons to be invisible, I'm simply going to click and drag on the canvas in the Viewer window to create boxes representing my buttons. (The size and placement of the buttons don't matter; these buttons will be invisible, remember.)

Note that the maximum number of buttons over video is determined by the type of track you're working with. For a 4:3 track, the maximum is 36. For a 16:9 track either letterbox or pan & scan, the maximum is 18. For a 16:9 track with both letterbox and pan & scan options enabled, your maximum is 12.

Now, one thing to keep in mind about these buttons is that they each have a numeric equivalent on the viewer's remote, just like menu buttons. Button 1 is 1; button 2 is 2; et cetera. And, just as with menu buttons, you have the option of offsetting these numerical values. So, for example, if you want button 1 to have the numerical equivalent on the remote of 40, then the offset value would be 39 (1+39=40). You set this offset value in the Inspector palette when you have a stream segment selected in the Track Editor.

Now, a couple comments about all of this. First off, not all players allow you to enter numerical values for navigation, and this includes especially the software players on some computers, include Apple's own player. Second, some viewers are going to be using universal remotes, which don't always allow you to enter values above 9. So just make sure that if you're going to have a widespread audience for your title that you don't make the numerical keypad entry a critical function of the presentation, or some people might not be able to view it properly.

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Related Keywords:apple dvd studio pro, dvd authoring, buttons over video, track buttons, interactive tracks

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