Double Density CD - Page 4

A DDCD medium is an 80 mm or a 120 mm disc with a continuously recorded physical track beginning from a radius of 24 mm and spiraling outward to a radius 37.5 mm or 58 mm. Like a conventional CD Drive/Media there are three types of DDCD Drive/Media, Read Only (DDCD-ROM), Write Once (DDCD-R), and ReWritable (DDCD- RW). The capacities of these media are the same. The DDCD Media Format is not backward compatible with current CD devices.

As you can understand, due to different physical structure, the DDCD Medium is not backwards compatible with the existing CD-ROM/DVD-ROM/CDR-W drives. This means that the media will only be playable in the devices that contains the "DDCD" logo.

For now there are not many manufacturers who ship DDCD-R/RW media. Only Sony and Verbatim sell DDCD-R/RW, and we haven't heard of any other media manufacturers going for it. Actually even Verbatim have announced DDCD media they haven't shipped in retail market due to low demand. Our guess is that they are waiting to see whether the new standard will be widely accepted from end users, in order to proceed to mass production. Below is a comparison chart beetween the CD/DDCD formats and the media that can be read/written:

As you may notice the DDCD drives can playback all CD media and DDCD media. The normal CD-RW drives simply cannot read the DDCD-R/RW media.

Comparing the new DDCD specifications with those of the conventional CD, some major specifications are the same, such as the size of the disc. Other specifications indicate that some adaptations have to be made to the media production process of the DDCD. Error correction and physical addressing require some changes to the decoding/encoding equipment.

Note: CIRC* is different from the conventional CD. In the DDCD system, the delay parameter “D” of CIRC is extended from 4 to 7 to improve burst error correction ability in case of higher recording density. The maximum burst error correction ability of CIRC* is extended to 837 symbols.