The DTS 5.1 Music Disc was a Compact Disc format offering surround sound audio, usually in the 5.1 configuration. The discs conformed to Red Book standard, so could be played in a standard CD player, but without the use of a DTS decoder all that would be heard is white noise. The potential confusion between DTS 5.1 Music Discs and standard Compact Discs meant some retailers were reluctant to stock them. There is some compression applied to the audio, so sound quality is arguably slightly lower than a standard CD.
Formats such as DVD-Audio and Super Audio CD, launched a few years later, could also offer surround sound and meant an end to the DTS 5.1 Music Disc, though several hundred titles were released on the format.
DTS surround sound technology is also used in movie theatres, on DVD-Video and on Blu-ray. It was also used on a small number of LaserDiscs.
QSound is an audio processing system introduced by QSound Labs. It was applied at the sound mixing stage and attempts to produce a surround sound effect from a stereophonic source. It was used on around 65 Compact Disc albums from 1991 to around 2001, which display the QSound logo. The first album to use QSound was Madonna’s ‘The Immaculate Collection’ and all the tracks were either re-mixed or mixed using the system.
No additional equipment was necessary to play a QSound Compact Disc, and the discs comply fully with Red Book standards.
As well as Compact Disc albums, the QSound technology was also applied to computer game audio, television programmes and film soundtracks.
On mono devices, music mixed using the QSound system can have elements missing.
Launched in 2004, The Fujifilm PhotoDisc CD-R is essentially a standard CD-R disc with a black substrate layer that claims to protect the data from ultra-violet and solar radiation. It also uses a different dye (phthalocyanine rather than the usual cyanine) in the recording layer, which should offer more resistance to heat and sunlight.
Although they are reported to be very reliable, for archival purposes gold archival CD-R discs are probably better.
Despite the name, the discs can be used for any purpose that a standard CD-R can be used for, and don’t just store photos.
MovieCD was a CD-ROM format for video, introduced by Sirius Publishing Inc. in early 1997, that allowed people to view full-length movies on their Windows PC or laptop using a standard CD-ROM drive.
MovieCDs could be played on PCs running Windows 3.1 and Windows 95 without the need for any additional hardware or software, and the PC hardware requirements were fairly modest. The necessary software and the MotionPixels codec were on the discs themselves and installed automatically.
Each disc could hold up to 45 minutes of video, so two or sometimes three discs were necessary for longer films. The resolution was 320×236 pixels, and the format promised ‘near-TV quality’ images (though of course, the format could only be played on a PC – there were no set-top MovieCD players available).
Over 100 titles were available on the MovieCD format including anime, music concerts and feature films. It competed with Video CD and the newly launched DVD-Video, and no version of MovieCD was developed for versions of Windows beyond Windows 95. It was not a commercial success and disappeared after a few years.
Using the discs on a post-Windows 98 system can cause problems with other video and audio software.
UHQCD is a type of audio Compact Disc introduced by Memory-Tech in Japan in 2015, and is a development of the HQCD (High Quality Compact Disc) introduced six years previously. UHQCD discs conform to Red Book standards and are playable in any audio CD player. They don’t contain any more audio information than a standard CD, but it is claimed that a higher-quality manufacturing process and higher quality materials in the reflective layer produces higher precision audio reproduction.
A photopolymer is used instead of standard polycarbonate, since in their liquid state photopolymers achieve better replication of the pits on the CD stamper.
As of 2017, there were over 900 titles available on UHQCD.
The Blu-spec CD was introduced in 2008 by Sony, and is a Red Book-compliant audio Compact Disc, so is playable on all audio Compact Disc players. Sony launched with 60 titles on Blu-spec CD.
Its name is derived from the shorter-wavelength blue laser used to create the master copy, which is claimed to produced more precise pits to reduce distortion due to reading errors, along with a new polymer polycarbonate developed for the Blu-ray Disc.
In 2012, a newer version called Blu-spec CD2 (or BSCD2) was introduced that claimed to have a more precise cutting machine and master discs made from silicon wafers. Sony called it Phase Transition Mastering.
Due to existing limitations of Compact Disc Digital Audio, it is debatable whether Blu-spec CDs offer better sound quality as there is no extra information stored on the disc.
As of 2017, new titles are still being released on both formats.
Minimax Compact Discs are generally CD singles which consist of a 3-inch playing area (equivalent to the mini CD single) surrounded by an area of translucent plastic (either clear or coloured) to make them full-size Compact Discs. The playable part of the disc conforms to Red Book standards.
On a normal Compact Disc, the reflective layer would continue to the edge of the disc, even if there was not enough music to fill it.
Because of the small playing area, minimax CDs can only hold a limited playing time (about 24 minutes maximum) and so have only been used for music singles or EPs.
They are very uncommon, presumably because of the extra expense in manufacturing them over a standard 5-inch CD single, but have been used for special edition singles, in much the same way as coloured vinyl records. It could be argued that the holographic CD is a form of minimax CD, as it is also formed of a mini CD single inside a larger area of plastic containing the holographic design.
Ultra Density Optical (UDO) is an optical disc data storage format that uses phase-change, and blue laser technology (similar to Blu-ray) to store substantial amounts of data on a disc in a cartridge very similar to the older 5.25-inch magneto-optical disc format that it was developed to replace.
UDO discs were first announced by Sony in 2000, and launched by Sony and Plasmon in 2003 with a capacity of 30 GB. UDO 2 was launched in 2007 with a capacity of 60 GB.
UDO discs are available in rewritable format, or as write once in which case the phase change method used means the data cannot altered once written (True WORM) making it very stable for long-term storage. A third format became available in 2005, Compliant WORM, that allows specific data on the disc to be destroyed while leaving other files intact.
As of 2017, UDO drives and discs are still available but since 2008 all brands of UDO disc have been manufactured by Mitsubishi in Japan.
Interactive DVDs (sometimes also known as DVD games, DVD Interactive or DVDi) allow the playing of games on DVD-Video players without the need for a computer or video game console, or any additional hardware (though some titles come with additional hardware such as buzzers).
The interactive DVD make use of the rudimentary interactivity features built-in to DVD-Video players that allow, for example, navigation through menus. The ability to skip to any point on the DVD instead of having to move through the video in a linear fashion as on VHS video recorders is also a major factor in making interactive DVDs practical.
The first interactive DVD game was Dragon’s Lair released in 1998, and a development of an older LaserDisc based game.
From 2001, DVD versions of board games and television quiz shows began to be released.
The original specification for Compact Disc Digital Audio, known as the Red Book, did not make any provision for copy protection, and by the late 1990s millions of ripped audio tracks from Compact Discs were compressed as MP3s and shared over the internet.
The music industry did several things to try and rectify the situation, including setting up online music stores selling music through a subscription model, and the Recording Industry Association of America also prosecuted over 20,000 individuals they accused of sharing pirated MP3s.
Starting around 2000, the music industry also began to put copy-protection onto audio Compact Discs. Companies such as EMI, Sony, BMG, and for a time Warner used copy protection as a means to prevent ripping of audio tracks onto a computer.
Since the discs were non-compliant with the Red Book standard, they were not supposed to display the Compact Disc Digital Audio logo on either the disc or inside the jewel case. There was also a consumer outcry against the disks as they prevented tracks from being copied to the purchaser’s personal audio devices, and some CD players such as those in cars would not play the disks (since these sometimes used some CD-ROM components, especially if they were intended to play disks containing MP3 or other types of compressed files).
In 2005, it was discovered that Sony BMG were using a type of copy protection called Extended Copy Protection (XCP) which installed a rootkit on a user’s computer. This sparked a scandal as it could be used by malware, and Sony announced a recall of disks using XCP and suspended its use.
EMI was the last major label to abandon copy protection in 2006.