 | |
| Media type | Optical disc |
|---|---|
| Encoding | Various |
| Capacity | Typically up to 800MB[citation needed] (up to 80 minutes audio) |
| Read mechanism | 780nm wavelength semiconductor laser |
| Standard | Red Book for audio |
| Developed by | Philips &Sony |
| Usage | Audio with primitive visuals |
| Extended from | CD-DA |
| Extended to | CD+EG |
CD+G (also known asCD-G,CD+Graphics andTV-Graphics[1]) is an extension of thecompact disc standard that can present low-resolution graphics alongside theaudio data on the disc when played on a compatible device. CD+G discs are often used forkaraoke machines, which use this functionality to present on-screen lyrics for the song contained on the disc. The CD+G specifications were published byPhilips andSony as an extension of theRed Book (CD standard) specifications.[2][1]
The first CD to be released with CD+G graphics wasEat or Be Eaten byFiresign Theatre in 1985.[3] TheCD+EG is a similar format that allows for better graphics, but has very rarely been implemented in releases.[2]
The CD+G format takes advantage of the sixCompact Disc subcode channels R through W (which are unused in standardCompact Disc Digital Audio), to provide 6 extra bits in CD+G for graphics information per 24 bytes of audio data. When a disc is read at normal speed, these six channels provide only 28.8kbit/s for graphics, which is enough to provide primitive visuals but which is dwarfed by modern bitrates (for comparison seebit rate § Video).[2][a]
In the CD+G system, 16-color (4-bit)raster graphics are constructed usingtiled rendering with 6×12pixel tiles (6 pixels wide and 12 lines high). These tiles are typically font definitions for text (such as for karaoke or info about the music). But the tiles can be used in any manner that tile rending permits, such as for fragments which combine together to represent a picture, or simply for patterns to decorate the background. These tiles are displayed in the main central 288×192 pixel area which is surrounded by a 1-tile thick border (for a total raster field of 300×216 pixels). The 16 colors are defined in acolor table, which can be manipulated to change the color scheme and simulate primitive animations.
The maininstructions for manipulating graphics are:
Compact Disc + Extended Graphics (CD+EG, also known asCD+XG andExtended TV-Graphics[1]) is an improved variant of theCompact Disc + Graphics (CD+G) format. Like CD+G, CD+EG utilizes basicaudio CD features to display text and video information in addition to the music being played. This extra data is stored in thesubcode channels R-W. Very few CD+EG discs have been published.[4]
Along with dedicated karaoke machines, other consumer devices that play CD+G format CDs include the NECTurboGrafx-CD (a CD-ROM peripheral for theTurboGrafx-16) andTurbo Duo, as well as the Japan-only successor thePC-FX, thePhilips CD-i, theSega CD,Sega Saturn,[5] the JVCX'Eye, the3DO Interactive Multiplayer, theAmiga CD32 andCommodore CDTV, and theAtari Jaguar CD (an attachment for theAtari Jaguar). Some CD-ROM drives can also read this data. Pioneer'sLaserActive player can also play CD+G discs, as long as either the PAC-S1/S-10 or PAC-N1/N10 game modules are installed.
Since 2003, some standaloneDVD players have supported the CD+G format. Regularaudio CD players will output only the audio tracks as if it was a normal music CD, unless otherwise designed to read the extra data (lyrics and images).[6]
CD+G karaoke albums are still made today by several UK and US manufacturers including Sunfly, Zoom Entertainments, SBI Karaoke and Vocal Star. Although the popularity of CD sales are dwindling the format is still widely used asMP3+G downloads.
Although CD+G found its market in karaoke entertainment, some music labels were keen to experiment with the format and a number of albums were released which featured graphic images, animations and text. These special edition CD+G releases are now very rare and have become collectible items as a result. Some albums released include:
Daiichi Kosho is a former karaoke music manufacturer and their high-quality edit-a-vision range of 99 CD+Gs is still highly sought after by karaoke presenters today.
CD+G karaoke CDs are often ripped onto computer hard drives asMP3+G, with the audio encoded in the standard audio format, MP3, and the graphics encoded in a RAW format. These can then be played on computers usingVLC media player, Karafun, or professionally byDJs and karaoke presenters using software such as Karma or AtomixVirtualDJ often in conjunction with aDJ controller manufactured byPioneer,Denon,Roland orNumark.
