Wired Movies and Sprites

Assigning Group IDs

Before QuickTime 3, sprites could only display images with the same image description. This restriction has been relaxed, but you must assign group IDs to sets of equivalent images in your key frame sample. For example, if the sample contains 10 images where the first 2 images are equivalent, and the last 8 images are equivalent, you could assign a group ID of 1000 to the first 2 images, and a group ID of 1001 to the last 8 images. This divides the images in the sample into two sets. The actual ID does not matter; it just needs to be a unique positive integer.

Each image in a sprite media key frame sample is assigned to a group. You add an atom of type kSpriteImageGroupIDAtomType as a child of the kSpriteImageAtomType atom and set its leaf data to a long containing the group ID.

You must assign group IDs to your sprite sample if you want a sprite to display images with non-equivalent image descriptions (i.e., images with different dimensions).