An implementation of limited multi-level (LML) optical recording

Multi-level pits and lands are mastered compatible with the compact disc (CD) format in a sub-channel on top of the original Runlength-Limited (RLL) channel, which remains unaffected. By introducing multi-level effects only in long pit and land runlengths of the main RLL channel, two additional Limited Multi-Level (LML) channels are created. Via the restriction of the multi-level modulation to relatively long runlengths, it is realized that the jitter in the original channel is not affected and that separate (independent) slicers for all pit multi-level effects and for the land multi-level effects can be used. An additional achievement is that a slicer is devised for retrieving the LML-bits which is optimized for maintaining a maximum capacity in the multi-level channel. The LML system is evaluated using both simulations and experiments on read-only discs.