An implementation of Limited Multi-Level (LML) optical recording

Multi-level pits and lands are mastered compatible with the compact disc (C D) format in a sub-channel on top of the original Runlength-Limited (RLL) c hannel, which remains unaffected. By introducing multi-level effects only i n long pit and land runlengths of the main RLL channel, two additional Limi ted Multi-Level (LML) channels are created. Via the restriction of the mult i-level modulation to relatively long runlengths, it is realized that the j itter in the original channel is not affected and that separate (independen t) slicers for all pit multi-level effects and for the land multi-level eff ects can be used. An additional achievement is that a slicer is devised for retrieving the LML-bits which is optimized for maintaining a maximum capac ity in the multi-level channel. The LML system is evaluated using both simu lations and experiments on read-only discs.