CD-i, or Compact Disc Interactive, is the name of an interactive multimedia CD player developed and marketed by Royal Philips Electronics N.V. CD-i also refers to the multimedia Compact Disc standard used by the CD-i console, also known as Green Book, which was developed by Philips and Sony (not to be confused with MMCD, the pre-DVD format also co-developed by Philips and Sony). Work on the CD-i began in 1984 and it was first publicly announced in 1986. The first Philips CD-i player, released in 1991 and initially priced around USD $700, is capable of playing interactive CD-i discs, Audio CDs, CD+G (CD+Graphics), Karaoke CDs, and Video CDs (VCDs), though the last requires an optional "Digital Video Card" to provide MPEG-1 decoding.