What is CD-i?

CD-i is an acronym which stands for Compact Disc Interactive or Interactive Compact Disc. CD-i uses the same basic Compact Disc as an Audio CD, a Video CD or a CD-ROM. All these systems use the same Compact Disc to store digital information. However each system retrieves and uses that information in a different way. A CD Audio player will read the Digital Audio files and play them through a Compact Disc Audio player.A Video CD will not only read Digital Audio files but Digital Video files as well. It then plays these files as Sound and Video on a Television using a Video CD player.CD-i also does this, but goes one stage further and adds Interactivity to the program. Now either the user can determine which order the files are read, or the software, which is also recorded on the disc can control the interactivity. For example, if the program asks a multiple choice question, what it does next can be determined by the answer the user gives. This basically gives the CD-i user control over what they see and in which order. The CD-i system uses a CD-i player to read the files and like Video CD, also displays them on an ordinary Television. Because a CD-i player has only one function in life, to read and display CD-i files it is very simple to operate, very reliable and relatively low in price considering the quality of the output.

Then there is CD-ROM. So why is a CD-ROM different? Well a CD-ROM or 'Read Only Memory' is designed to work with a Computer, which reads the files, processes them and displays them on a Computer Monitor. A Computer is capable of many tasks and comes in many different types, formats and speeds. CD-ROMs can either be made for a specific type and speed computer, in which case that is the only one they will play on, or they can be made down to the lowest common denominator and run on several different types of computer, but at a lower standard of output.

The most obvious example of this is the way the systems show Video. For CD-i the Video is encoded as an MPEG stream and any CD-i player fitted with a Digital Video Cartridge,(They come standard that way now) can play that MPEG stream at 32 frames per second using the full size Television screen, no matter how large. Computers on the other hand, have to use various different types of video most of them very low standard, having either quarter screen size, or half speed (15 frames per second), most computer do both. The results are very unsatisfactory. Some computers are able to play Full Motion MPEG at full screen size, these are still quite rare and very expensive.Annother difference is simplicity of use. Almost every body can place the CD-i disc into a CD-i player and it will work. Very few of us are able to do the same with a CD-ROM in a computer. In short CD-i is a Television Bases multimedia system created for people who prefer Television to Computers and for those of us looking for a platform which is simple, low cost, an International Standard and which we and our users can install and operate without training or being an Einstein.

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