MultiLevel Recording

MultiLevel Recording (ML, also known as M-ary) is a technology originally developed by Optex Corporation[1] and promoted by Calimetrics to increase the storage capacity of optical discs.

Members eventually included Calimetrics, TDK, Sanyo Semiconductor, Plextor, Matsushita Kotobuki Electronics, Mitsubishi Chemical Corporation, Verbatim, Teac and Yamaha.

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.

To compensate, the ML logical-format devotes a substantial portion of bits (as forward-error correction coding) to enhance robustness against media defects and signal noise.

Multi-layer and multiLevel technique can be combined (as in dual-layer ML-DVD ROM), where ML-modulation is applied to each individual layer of the disc.