Rewritable DVD-ROM drives, or DVD-RAM, employs phase-change technology with some MO features mixed in rather than the pure optical technology of CD and DVD discs and has its roots in the PD optical disc system. A land groove format allows signals to be recorded on both the grooves formed on the disc and in the lands between the grooves. The grooves and pre-embossed sector headers are moulded into the disc during manufacturing. The first generation of DVD-RAM products – providing 2.6GB of reusable data space on either side of a disc – first appeared in mid-1998. Information Processing System Video process the raw data generated by data silos and convert them into understandable terms such as statistics. However, these early drives will be incompatible with the higher-capacity standard, which may use a contrast enhancement layer and a thermal buffer layer to achieve higher density.