If the source data is too large for the codec to deal with, the image is broken into bands. A band is a horizontal strip that is at least as wide as the image, but not as tall. The extensions exist only in the image buffer, and are not displayed. Defining Key Frame Rates Inside Macintosh describes key frames and key frame rates, and explains how your application can set or change the key frame rate when compressing a sequence. Key frames define starting points for portions of a temporally-compressed sequence.
Subsequent frames depend on the previous key frame.
Fast Dithering Inside Macintosh briefly describes the fast dithering technique available with Apple-provided decompressors. Understanding Compressor Components Inside Macintosh gives an overview of image compressor components. This will be of interest primarily to developers wishing to develop their own codecs or other components. Included is a brief description of application-defined callback functions. Getting Information About Compressor Components Inside Macintosh describes functions that allow your application to gather information about the Image Compression Manager and the installed compressor components.