Tech Primer

Versatile Multi-layer Disc

The versatile multi-layer disc (VMD) is a next generation optical disc standard designed for high-definition content including motion pictures, gaming, recordings of TV shows and sports broadcasts. This format could potentially do away with the ongoing Hi-Def wars between Sony’s Blue Ray and the Toshiba-led consortium’s HD-DVD formats. Hollywood production houses are undecided about the format to back, and this, analysts fear, could lead to the public waiting and watching—something which would make it an uphill task to sell high-definition products. VMD can support both formats on a single disc.

More layers, same manufacturing setup

An advantage of this technology is that the current DVD manufacturing process doesn’t have to be changed in any way, shape or form to press these discs. Even the way in which content is replicated will not undergo too much of a change. The VMD drive is also quite similar to a standard DVD player with small modifications being needed for the multi-layer read out. Moreover, a VMD player can play existing DVD formats. The format is suited for high-definition content and the underlying technology is based on the existing Red Laser technology. As the discs are multi-layered, capacity is substantially higher.

Polymer-based technology

As with DVD technology, VMDs are polymer-based, a polymeric master is created with grooves that act as information pits using either the popular injection moulding or the photo polymeric replication method. This is followed by depositing a partially reflective layer on the surface of the master. A few information layers are deposited on this substrate. Information is recorded in the form of pits in each of these layers. A separating layer is used to distance neighbouring data layers.

A VMD is exactly the same width and thickness as a conventional CD / DVD. The drives have a transfer rate of 40 Mbps. H.264, VC-1 and MPEG-2 and 4 encoding are supported. A VMD is currently capable of holding 50 GB; however, manufacturers claim that, in the future, blue laser VMDs will be able to hold around 300 GB.

Copy protection remains

Since the DVD and the VMD are fully compatible, similar data protection algorithms can be employed. Content Scramble System (CSS) is a scheme that is employed to prevent video files from being copied directly from VMDs. Content Protection for Pre-recorded Media is an enhancement over the CSS, which is used to protect VMD-Audio. Also employed is the Serial Copy Generation Management System. This technology prevents copying of initial copies, that is, making second or third generation copies.

How the players stack up

The key difference between a VMD player and a DVD player is that the VMD player comes with a HD Decoder, which enables the viewer to watch a real high-def quality video. The pick-up head in a VMD player includes lasers, mobile actuators and lenses for picking up the reflected laser beam and passing it over to a multi-faceted photo diode receptor which receives the signal from the VMD disc. The player has a CPU that controls its functions.

Possible applications

The biggest advantage of the VMD is storage capacity, several movies can be recorded into one VMD, and in that sense it can hold multiple DVDs. It will facilitate the mobile storage of large databases and software applications. VMD manufacturers guarantee superior visual quality. Gaming companies will probably be early adopters.

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