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Creating a QTKit Stop or Still Motion Application

Now that you've worked through the examples in the previous chapters of this guide—building and extending the functionality of your QTKit capture player application, adding audio and DV camera support—you'll be ready to take on another coding assignment. The goal here is, once again, to extend your knowledge of the QTKit capture API.

Because the API supports frame-accurate, real-time motion capture, you'll discover a broad range of possible uses and applications. One such usage is still or stop motion animation. This is a popular animation technique first introduced in Walt Disney’s 1959 classic film Noah’s Ark. Basically, it involves making still objects appear as if they are in motion by adding single frames together into a movie. It’s a way of animating objects and bringing them visually to life on the screen. Stop or still motion animators have employed this technique—making static objects appear to move when played back at normal speed—in countless movies, TV commercials, and TV shows since the days of Disney.

Following the steps outlined in this chapter, you'll construct a simple still motion capture application that lets you capture a live video feed, grab frames one at a time with great accuracy, and then record the output of those frames to a QuickTime movie. You’ll be able to accomplish this with less than 100 lines of Objective-C code, constructing the sample as you’ve done in previous chapters, in Xcode 3 and Interface Builder 3.

In building your still motion capture application, you’ll work with the following three QTKit classes:

• QTCaptureSession. The primary interface for capturing media streams.

• QTCaptureDecompressedVideoOutput. The output destination for a QTCaptureSession object that you can use to process decompressed frames from the video that is being captured. Using the methods provided in this class, you can produce decompressed video frames that are suitable for high-quality video processing.

• QTCaptureDeviceInput. The input source for media devices, such as cameras and microphones.

Contents:

Set Up Your Project
Prototype the Still Motion Capture Application
Create the Project Using Xcode 3
Create the User Interface Using Interface Builder 3
Prepare to Capture Single Frame Video
Complete the Project Nib File in Xcode
Implement and Build Your Still Motion Capture Application

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