Digital video is still far from elegant, both in the way it handles and in the way it looks. Any off the shelf computer, however putatively powerful, is still not able to show full-frame, full-screen video, whatever various manufacturers claim (I even question whether the new MMX Intel chip will be able to do this, although I don't speak from personal experience or knowledge). Imagine! uses full frame video images, but rarely running at full framerate, and only with a minimum of 50MB or RAM allocated to it (at least, that was true the last time I saw it running a few months ago). Director handles digital video badly. The amount of processor overhead the program itself demands leaves too little oomph to drive video well at much beyond 320X240 (half screen size). This has serious implications for performance, of course, where full frame video is highly desirable. Director, at least, can "dress" half-screen nicely, leaving room for text or other full screen still images, it at least goes part way towards alleviating the distress caused by all that empty space.
The solution, of course, is to compress the video data, reducing the required data rate so that the processor (and, particularly in the case of CD-ROM, the disk) has time to catch up. A distinction needs to be drawn here between compressors (or codecs (compressors/decompressors) as they are more typically referred to) which merely reduce the size of the file, and codecs which not only reduce the size of the file, but conform it to a specific data rate. Some codecs are essentially realtime, such as Apple's Video codec, others are much slower, such as JPEG and MPEG. There are a variety of codecs currently in use, but the ones most pertinent to this discussion are Cinepak (used primarily on the Macintosh) and Indeo (used primarily on Windows machines), both of which provide the user with control over the final data rate, in Kbytes per second.
Roll on the day when this is no longer an issue...
