MultiLevel Recording

MultiLevel Recording (ML, also known as M-ary) is a technology originally developed by Optex Corporation and promoted by Calimetrics to increase the storage capacity of optical discs. It failed to establish itself in the market. Through a combination of proprietary media, recorder, reader, and player modifications, Calimetrics proposed that ML could increase the capacity of a CD-ROM, CD-R, or CD-RW to 2 GB; a single-layer DVD, DVD-R, DVD+R, DVD-RW, DVD+RW, or DVD-RAM to 7.1 to 10 GB; and a single-layer Blu-ray Disc (BD) to as much as 60 GB. An optionally integrated digital rights management (DRM) system called MovieGuard was also suggested. An industry group called the ML Alliance was formed in 2000 to help commercialize ML technology. Members eventually included Calimetrics, TDK, Sanyo Semiconductor, Plextor, Matsushita Kotobuki Electronics, Mitsubishi Chemical Corporation, Verbatim, TEACr and Yamaha.

Several 2 GB ML CD-based recorders were developed for release in 2002 (TDK's MLCDRW1000 and Plextor's PX-ML3630), but never came to market. This was largely a business decision influenced by the rapid fall of CD-R/RW prices and the simultaneous rise in popularity of writable DVD technology. Calimetrics went on to work on more advanced DVD and Blu-ray Disc versions of their technology, including a proposal to build a next generation version of Enhanced Versatile Disc (EVD). Calimetrics ceased operations in 2004.