compact disc interactive (CD-I)
The specifications for CD-I(Compact Disc Interactive) were published by Philips back in 1986 and specified in the Green Book. The CD-I format can contain data, graphics, video and audio. Based on this, special CD-I players were developed. Commercially available televisions are suitable as output devices, although an interface for connection to a PC is also available.
CD-Is can be used for POS( point of sale) applications in the public and business sectors, where the prospective customer himself can interactively call up the desired information. Direct branching is possible between the individual sequences and files.
The CD-I operates with a sampling rate of 37.8 kHz and a resulting bandwidth of 17 kHz. There are three different levels, marked "A", "B" and "C". All three levels use adaptive delta pulse code modulation( ADPCM) for coding. The level "A" has an 8-bit, the levels "B" and "C" with 4-bit coding. In addition to the different number of channels 2/4 for A, 4/8 for B and 8/16 for "C", the different levels differ in recording duration and signal-to- noise ratio, which is highest for level A at 96 dB.