DualDisc is a type of double-sided optical disc product developed by a group of record companies including EMI Music, Universal Music Group, Sony/BMG Music Entertainment, Warner Music Group, and 5.1 Entertainment Group and now under the aegis of the Recording Industry Association of America (RIAA). It features an audio layer similar to a CD (but not following the Red Book CD Specifications) on one side and a standard DVD layer on the other. In this respect it is similar to, but distinct from, the DVD Plus invented in Europe by Dieter Dierks and covered by European patents.

DualDiscs first appeared in the United States in March 2004 as part of a marketing test conducted by the same five record companies who developed the product. The test involved thirteen titles being released to a limited number of retailers in the Boston, Massachusetts, and Seattle, Washington, markets. The test marketing was seen as a success after 82% of respondents to a survey (which was included with the test titles) said that DualDiscs met or exceeded their expectations. In addition, 90% of respondents said that they would recommend DualDisc to a friend.

DualDisc titles received a mass rollout to retailers throughout the United States in February, 2005, though some titles were available as early as November, 2004. The recording industry had nearly 200 DualDisc titles available by the end of 2005 and over 2,000,000 units had been sold by the middle of that year.

How a DualDisc works

DualDiscs appear to be based on double-sided DVD technology such as DVD-10, DVD-14 and DVD-18 except that DualDisc technology replaces one of the DVD sides with a CD. The discs are made by fusing together a standard 0.6 mm-thick DVD layer (4.7-gigabyte storage capacity) to a 0.9 mm-thick CD layer (60-minute or 525-megabyte storage capacity), resulting in a 1.5 mm-thick double-sided hybrid disc that contains CD content on one side and DVD content on the other.

The challenge for the designers of DualDisc was to produce a dual-sided disc which was not too thick to play reliably in slot-loading drives, while the CD side was not too thin to be tracked easily by the laser. DVD Plus, though conceptually similar, uses a thicker CD layer and thus is more likely to get stuck in a slot-loading player (although this appears to be almost unknown); DualDisc takes the other course by thinning the CD layer.

Because the 0.9 mm thickness of the DualDisc CD layer does not conform to Red Book CD Specifications, which call for a layer no less than 1.1 mm thick, some CD players may not be able to play the CD side of a DualDisc due to a phenomenon called spherical aberration. As a result, the laser reading the CD side might get a 'blurry' picture of the data on the disc; the equivalent of a human reading a book with glasses of the wrong strength. Engineers have tried to get around this by making the pits in the CD layer larger than on a conventional CD. This makes the CD side easier for the laser to read; equivalent to the book using bigger print to make it easier to see, even if the person's glasses are of the wrong strength. The downside to this, however, is that the playing time for the CD layer of some early DualDiscs decreased, from the standard 74 minutes of a conventional CD, to around 60 minutes, although this early limitation now appears to have been overcome.

Because the DualDisc CD layer does not conform to Red Book specifications, Philips and Sony have refused to allow DualDisc titles to carry the CD logo and most DualDiscs contain one of two warnings:

'This disc is intended to play on standard DVD and CD players. May not play on certain car, slot load players and mega-disc changers.'
'The audio side of this disc does not conform to CD specifications and therefore not all DVD and CD players will play the audio side of this disc.'

The DVD side of a DualDisc completely conforms to the specifications set forth by the DVD Forum and DualDiscs have been cleared to use the DVD logo.

Hopes for DualDisc

Record companies have two main hopes for DualDiscs; the first being that they will eventually replace CDs as the preferred media for purchase at music retailers, and the second being that the inclusion of bonus DVD content at a price similar to a conventional CD will help to slow down online music piracy by giving consumers more incentive to buy their music through retailers. Some titles such as Devils & Dust by Bruce Springsteen and Straight Outta Lynwood by 'Weird Al' Yankovic have been released in the United States on DualDisc only.

Costs versus conventional CDs

In the US, the cost of a DualDisc at retail versus that of a conventional CD varies depending on the title but, on average, a DualDisc costs about $1.50 to $2.50 USD more than the same title on CD. Some DualDisc titles such as Mr. A-Z by Jason Mraz and In Your Honor by the Foo Fighters have enhanced packaging which increases the retail cost of the DualDisc version of the albums over their CD counterparts more than the average. There are also other factors which go into the additional costs such as production, marketing etc.

Common DVD content

What one finds on the DVD side of a DualDisc title will vary. Common content includes:

* The entire album in higher-quality stereophonic and/or surround sound.
* Documentaries
* Music videos
* The artist's discography
* A link to the artist's website

Audio types

The CD side of a DualDisc contains standard 16-bit LPCM audio sampled at 44.1 kHz. On the DVD side, most record companies, with the notable exception of Sony Music, provide the album's music in both high-resolution, 24-bit DVD-Audio (typically at a sample rate of 96 or 192 kHz for stereo and 48 or 96 kHz for surround sound) and lower-resolution, 16-bit Dolby Digital sound (typically sampled at 48 kHz). This is done to allow consumers with DVD-Audio players access to very high-resolution stereophonic and/or surround sound versions of the album while also providing the lower-resolution Dolby Digital stereophonic and/or surround sound which is compatible with any DVD player.

Because Sony has a high-resolution audio format, SACD, in the marketplace which directly competes with DVD-Audio (see next section), Sony Music, as a general rule, only provides 16-bit, 48 kHz sampled LPCM stereophonic (and sometimes Dolby Digital Surround) sound on the DVD side of their DualDiscs. The sound is compatible with any DVD player; however, it does not provide the higher fidelity and resolution of 24-bit, high sample-rate DVD-Audio.

Competition

The biggest competition to DualDisc is the hybrid Super Audio CD (SACD), which was developed by Sony and Philips Electronics, the same companies that created the CD. DualDiscs and hybrid SACDs are competing solutions to the problem of providing higher-resolution audio on a disc that can still be played on conventional CD players.

DualDiscs take the approach of using a double-sided disc to provide the necessary backwards compatibility; hybrid SACDs are a one-sided solution that instead use two layers: a conventional CD layer and a high-resolution layer.

Lasers in conventional CD players have a different wavelength (typically around 780 nm) than those in SACD players (650 nm). Hybrid SACDs possess a special high density layer that is transparent to the conventional CD player's laser but is partially reflected by the SACD player's laser. When a hybrid SACD is placed into a conventional CD player, the laser beam passes through the high-resolution layer and is reflected by the conventional layer at the regular 1.2 mm distance. The result is that the hybrid disc plays as normal.

When a hybrid disc is placed into an SACD player, the laser is partially reflected by the high-resolution layer (at 0.6 mm distance) before it can reach the conventional layer. If a conventional CD is placed into an SACD player, the laser will read the disc without incident since there is no high-resolution layer to reflect. Because of the difference between the working distances of CDs and SACDs, the aperture of the lens in the SACD player must be adjusted to obtain the correct focal length.

Hybrid SACDs claim a higher compatibility rate with conventional CD players than DualDisc, due to the fact that hybrid SACDs conform to Red Book standards. However, a SACD or SACD-capable DVD player is required to take advantage of the enhanced SACD layer. With a DualDisc, consumers can use their existing DVD player to hear surround mixes. (DVD-Audio capable players are required for higher-resolution audio, if present.) It is currently estimated that 75% of households in the United States have at least one DVD player.

In addition, several SonyBMG titles whose regular editions include copy protection programs (such as XCP and SunnComm) do not feature the software on the DualDisc versions.

Criticisms

There are numerous criticisms about DualDiscs, ranging from size to DualDiscs being more fragile than conventional CDs.

Consumer complaints

In addition to the possible inability for some CD players to read a DualDisc properly, other consumer criticisms of DualDisc include:

- The 1.5 mm-thick disc can get jammed in slot loading computer DVD drives, DVD players, slot-loading CD players (such as car CD players) and mega-changers. This may even damage the disc.
- For any CD player, the thinner CD layer makes reading the CD side of a DualDisc harder than reading a conventional CD. Thus, anomalies such as small scratches, fingerprints or disc tilt may cause tracking errors more easily than those same anomalies would on a conventional CD. Since disc damage is inevitable over time, this can mean a reduction in a DualDisc's effective lifetime as compared to a CD.
- Players that use a DVD drive (whether the player plays DVDs or not: some high-spec CD players are like this) can generally not play the CD side. This problem (and those above) could be completely solved by manufacturing using a different material for the disc. The DVD side of a DualDisc is required to offer at least the same quality of audio as the CD side (eg 16-bit, 48kHz PCM) or better, so as a result owners of DVD players should simply play the DVD side. (However, this is not necessarily as simple as playing a CD: you have to navigate menus; although DVD-A content should be authored so as not to require a video monitor.)
- The recommended 60-minute limit of the CD side prohibits it from including the entire content of some conventional CDs (although this limitation may have been overcome). When record companies have wanted to issue extended content that exceeds the current capabilities of DualDisc (eg a very long CD side or requiring a double-layer DVD, which is currently under development for DualDisc), they have generally opted for a 'DoubleDisc' package: a single package containing a regular CD and a DVD-Audio/Video disc.
- Since both sides of the disc are used for data, a label cannot appear on either side of the disc. The only way that a consumer knows which side is CD and which is DVD is by looking at the center ring of the disc where it is marked. However there are now labelling technologies that are transparent to laser light but visible in normal light, which can in theory be used to label any type of double-sided disc.

Manufacturer warnings

A number of electronics companies such as Lexicon, Marantz, Mark Levinson, Onkyo, Panasonic, Pioneer, and Sony (both its Computer Entertainment and Electronics divisions) issued statements warning consumers about possible problems with playing DualDisc titles on their equipment.

These warnings ranged in severity from DualDiscs just not working with the equipment to actual damage to the disc and/or equipment. Meridian Audio, Ltd., on the other hand, issued a statement that 'no harm or damage whatsoever' would be caused to the player or the disc if DualDiscs were used on their equipment, but noted that their players with DVD drives would not reliably play the CD layer.

How the warnings came about is something of a mystery. Pioneer USA's was one of the first, but when questioned on this topic by staff at Pioneer UK, it appeared to have no technical basis and originated in the marketing department.[citation needed] It is likely that Pioneer USA, Harman and some other companies issued the warnings to cover themselves against possible legal action as had been the case with early DVDs and DVD players, where combinations of evolving specifications and manufacturing techniques led to initial incompatibilities. In fact the return rate of DualDiscs has been extremely small, and as a result disc manufacturers and record companies have been reluctant to address the comparatively minor issues that remain.

Legal controversy

There has been some controversy surrounding the DualDisc format, as Dieter Dierks, the inventor of the DVD Plus specification, claims that DualDisc technology is in violation of his European patents. This delayed the release of DualDisc titles in Europe, with them eventually hitting European shores in September 2005. The first British artist to announce a DualDisc release of his album was Sony/BMG recording artist Will Young.

Wikipedia information about DualDisc. This article is licensed under the GNU Free Documentation License . It uses material from the Wikipedia article 'DualDisc'