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
5D DVD with a capacity of 10 terabytes, approximately 2000 times the capacity of a standard DVD, compared to Holographic Versatile Disc technology, which has an estimated maximum disc capacity of 6 terabytes. The similarity of disc writing would also make it easier to make 5D DVD players backwards-compatible with existing CD and DVD technology. 5D DVD A 5D DVD is a digital storage medium akin to a DVD being developed by Peter Zijlstra, James Chon and Min Gu at the Swinburne University of Technology in Melbourne, Australia. In 2009, the developers estimated that the technology could be commercially ready in five