Compact disc format used primarily for karaoke discs
CD+G
(also known as
CD-G
,
CD+Graphics
and
TV-Graphics
[1]
) is an extension of the
compact disc
standard that can present low-resolution graphics alongside the
audio data
on the disc when played on a compatible device. CD+G discs are often used for
karaoke
machines, which use this functionality to present on-screen lyrics for the song contained on the disc. The CD+G specifications were published by
Philips
and
Sony
as an extension of the
Red Book
(CD standard) specifications.
[2]
[1]
The first CD to be released with CD+G graphics was
Eat or Be Eaten
by
Firesign Theatre
in 1985.
[3]
The
CD+EG
is a similar format that allows for better graphics, but has very rarely been implemented in releases.
[2]
Design
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The CD+G format takes advantage of the six
Compact Disc subcode
channels R through W (which are unused in standard
Compact 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 28.8
kbit/s
for graphics, which is enough to provide primitive visuals but which is dwarfed by modern bitrates (for comparison see
bit rate § Video
).
[2]
[a]
In the CD+G system, 16-color (4-bit)
raster graphics
are constructed using
tiled rendering
with 6×12
pixel
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 a
color table
, which can be manipulated to change the color scheme and simulate primitive animations.
Instruction set
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The main
instructions
for manipulating graphics are:
- Memory Preset: Set the screen to a particular color.
- Border Preset: Set the border of the screen to a particular color.
- Tile Block (Normal): Load a 12×6 tile, 2 color tile and display it normally.
- Scroll
Preset: Scroll the image, filling in the new area with a color.
- Scroll Copy: Scroll the image, rotating the bits back around.
- Define Transparent Color: Define a specific color as being transparent.
- Load Color Table (entries 0?7): Load in the lower 8 entries of the color table.
- Load Color Table (entries 8?15): Load in the upper 8 entries of the color table.
- Tile Block (
XOR
): Load a 12×6 tile, 2 color tile and display it using the XOR method.
Improvements
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Compact Disc + Extended Graphics
(
CD+EG
, also known as
CD+XG
and
Extended TV-Graphics
[1]
) is an improved variant of the
Compact Disc
+ Graphics (CD+G) format. Like CD+G, CD+EG utilizes basic
audio CD
features to display text and video information in addition to the music being played. This extra data is stored in the
subcode channels
R-W. Very few, if any, CD+EG discs have been published.
[2]
- 288
pixels
per line
- 192 lines
- up to 256 colors
Usage
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Along with dedicated karaoke machines, other consumer devices that play CD+G format CDs include the NEC
TurboGrafx-CD
(a CD-ROM peripheral for the
TurboGrafx-16
) and
Turbo Duo
, as well as the Japan-only successor the
PC-FX
, the
Philips CD-i
, the
Sega CD
,
Sega Saturn
,
[4]
the JVC
X'Eye
, the
3DO Interactive Multiplayer
, the
Amiga CD32
and
Commodore CDTV
, and the
Atari Jaguar CD
(an attachment for the
Atari Jaguar
). Some CD-ROM drives can also read this data. Pioneer's
LaserActive
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 standalone
DVD players
have supported the CD+G format. Regular
audio 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).
[5]
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 as
MP3+G
downloads.
Notable releases
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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 as
MP3+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 using
VLC media player
, Karafun, or professionally by
DJs
and karaoke presenters using software such as Karma or Atomix
VirtualDJ
often in conjunction with a
DJ controller
manufactured by
Pioneer
,
Denon
,
Roland
or
Numark
.
Notes
[
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]
- ^
The document does contain a number of errors, later discovered.
References
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External links
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]