Double-density compact disc

Double-density compact disc (DDCD) is an optical disc technology developed by Sony using the same laser wave-length as compact disc, namely 780 nm. The format is defined by the purple book standard document.

For a 120 mm disc, it doubles the original 650 MB to 1.3 GB capacity of a CD on recordable (DDCD-R) and rewritable (DDCD-RW) discs by narrowing the track pitch from 1.6 to 1.1 micrometers, and shortening the minimum pit length from 0.833 to 0.623 micrometer. The DDCD was also available in read-only format (DDCD-ROM). All three formats existed also in small 80 mm discs.

The technology failed to acquire significant market share before the success of DVD technology. The DVD technology offered a significantly higher capacity (four times more initially with 4.7 GB on single layer discs, 8.5 GB on dual layer discs to a max of 17.08GB on a dual-side+dual layer disc).

The only DDCD recorder introduced was the Sony CRX200E.

The technology was marked as 'legacy' in the 2006-edition of the SCSI MultiMedia Commands command set.

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