CD player in 1970. Following litigation, Sony and Philips licensed Russell's patents (then held by a Canadian company, Optical Recording Corp.) in the 1980s. The Compact Disc is an evolution of LaserDisc technology, where a focused laser beam is used that enables the high information density required for high-quality digital audio signals. Prototypes were developed by Philips and Sony independently in the late 1970s. In 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc. After a year of experimentation and discussion, the "Red Book" CD-DA standard was published in 1980. After their
Video CD audio frequency range is limited to those sounds most clearly heard by the human ear. The VCD standard also features the option of DVD-quality still images/slide shows with audio, at resolutions of 704×480 (NTSC) or 704×576 (PAL/SECAM). Version 2.0 also adds the playback control (PBC), featuring a simple menu like DVD-Video. Shortly before the advent of White Book VCD, Philips started releasing movies in the Green Book CD-i format, calling the subformat CD-i Digital Video (CD-i DV). While these used a similar format (MPEG-1), due to minor differences between the standards these discs are not compatible with VCD players. Philips'