When I attend the Consumer Electronics Show (CES) in Las Vegas each January, I don't expect to find new technology that is applicable to music production. This year, however, I was surprised to discover something that could become ubiquitous in standalone and computer-based digital audio workstations. TDK (www.tdk.com) was demonstrating a new recording technology that promises to triple the capacity of CD-R/RW discs — that's right, a standard-size CD-R or CD-RW that can hold as much as 2 GB.
This technology, called MultiLevel (ML), was developed by Calimetrics (www.calimetrics.com), a small Silicon Valley firm that has entered into a marketing partnership with TDK. The beauty of ML is its simplicity; a conventional CD-R/RW drive can be upgraded to ML capability with the addition of a single controller chip and some firmware modifications. The drive's optics and mechanics remain unaltered. ML does require special blank discs, which TDK calls ML-R and ML-RW. These discs will be available for about $2 and $3, respectively.
Instead of burning pits of different lengths into the disc's recording layer, ML defines “data cells” that are a uniform length of 600 nanometers (nm). By comparison, conventional CDs burn pits that range in size from 833 to 3,000 nm. The write laser burns a nonreflective circular spot into each cell, and the diameter of the spot determines the amount of light reflected from the cell as the data is read. The current implementation can accommodate eight spot sizes that result in eight levels of reflectivity. Thus, each data cell represents three bits (23 = 8) instead of one as it would in a conventional CD, tripling the capacity of the disc (see Fig. 1).
ML offers other advantages over conventional CD-R/RW. For example, the new format writes data sequentially rather than interleaving it, which avoids any buffer-underrun problems. That requires a different sort of error-correction code (ECC) to recover lost data during playback, and ML uses a Reed-Solomon product code that is similar to the ECC used on DVDs. In addition, ML does not require finalization; the table of contents (TOC) for each session is written separately, and ML players read those TOCs to find the data on the disc.
ML-R and ML-RW blanks use organic dye and phase-change alloy recording layers, respectively, much like CD-Rs and CD-RWs. However, the new materials are slightly different from their conventional counterparts because ML marks are smaller than the marks on a CD, so the recording layer must be “tuned” for that size range. Still, blanks can be manufactured with existing facilities, greatly reducing production costs.
In addition to standard-size ML blanks that measure 12 cm in diameter, TDK is making two smaller sizes: 8 cm, which holds 650 MB of data, and 6 cm, which holds 200 MB. At CES the company also announced a computer-based internal ML drive that can write data at more than 5 MB per second, which will fill a 2 GB disc in less than six minutes. The drive can also read and write normal CD-R/RW discs, but ML discs require an ML player.
Calimetrics is working to apply ML technology to recordable DVD; recent experiments increased the data density by a factor of 2.1 using 12 reflectivity levels. (DVDs record data and correct errors more efficiently than CDs, so the relationship between data density and number of levels is not equivalent.) The result is a capacity of 10 GB using current technology, and that could easily increase to 30 GB or more using blue lasers. In any event, ML is an exciting new technology that could have a major impact on optical media storage.