What is a real-time system?
in section 3 of this FAQ), it is very important that the audio and video are placed in the correct way on the disc. Unlike other non-realtime systems like PCs with a CD-ROM drive which can store large amounts of audio and video data in memory for later playback (and hence requiring more complicated and expensive systems), a CD-i player reproduces the audio and video data in realtime when it is being read from the disc.