HD DVD had declined to say whether the 51 GB disc was compatible with existing drives and players. Specification 2.0 Part 1 (Physical Specification) for triple layer HD DVD had been approved in November 2007. At the CES 2007, Ritek revealed their high definition optical disc process that extended both competing high definition formats to ten layers, increasing capacity to 150 GB for HD DVD and 250 GB for Blu-ray Disc. A major obstacle to implementing this technology in either format (150 GB HD DVD will not be developed due to HD DVD's discontinuation) is that reader-writer technology available may not be
Optical disc current third-generation discs and have the potential to hold more than one terabyte (1 TB) of data and meant for distributing Ultra HD video : There are numerous formats of optical direct to disk recording devices on the market, all of which are based on using a laser to change the reflectivity of the digital recording medium in order to duplicate the effects of the pits and lands created when a commercial optical disc is pressed. Formats such as CD-R and DVD-R are "Write once read many", while CD-RW and DVD-RW are rewritable, more like a magnetic recording hard disk