Wired Movies and Sprites

About the Sprite Media Handler

The sprite media handler is a media handler that makes it possible to add a track containing a sprite animation to a QuickTime movie. The sprite media handler provides routines for manipulating the sprites and images in a sprite track.

The sprite media handler makes use of routines provided by the sprite toolbox. For background information about sprites, sprite animation, and the sprite toolbox, see Chapter 1, "Introduction to Wired Movies, Sprites, and the Sprite Toolbox."

As with sprites created in a sprite world, sprites in a sprite track have properties that define their locations, images, and appearance. However, you create the sprite track and its sprites differently than you create the sprites in a sprite world.

A sprite track is defined by one or more key frame samples, each followed by any number of override samples. A key frame sample and its subsequent override samples define a scene in the sprite track. A key frame sample is a QT atom container that contains atoms defining the sprites in the scene and their initial properties. The override samples are other QT atom containers that contain atoms that modify sprite properties, thereby animating the sprites in the scene. A sprite track sample is a QT atom container structure. In addition to defining properties for individual sprites, you can also define properties that apply to an entire sprite track.

For more information about QT atoms and atom containers, see Chapter 1, "Introduction to Wired Movies, Sprites, and the Sprite Toolbox."

A key frame sample also contains all of the images used by the sprites. This allows the sprites in a sprite track to share image data. The images consist of two parts, an image description handle (ImageDescriptionHandle ) concatenated with compressed image data. The image description handle describes the compressed image. You can compress the image using any QuickTime codec.

Images are stored in a key frame sample by index; each sprite has an image index property (kSpritePropertyImageIndex ) that specifies the sprite's current image. All images assigned to a sprite must be created using the same image description, unless you use group IDs.

The matrix, layer, visible, and graphics mode sprite properties have the same meaning for a sprite in a sprite track as for a sprite created in a sprite world.

As with sprite worlds, you can create a sprite track that has a solid background color, a background image composed of the images of one or more background sprites, or both a background color and a background image.

About the Sprite Media Handler

Hit Testing Flags

Key Frame Samples and Override Samples

Sprite Track Media Format

Sprite Track Properties

Alternate Sources for Sprite Image Data