DVD Forum, the international organization that oversees standardization of DVD and HD DVD optical disc formats, has finally approved version 2.0 of triple-layer HD DVD discs. The availability of physical specification of an HD DVD read-only media that can hold up to 51GB of data will allow the manufacturers to start producing the appropriate disks, whereas content producers may now start to think about how to use additional capacity.

The approval of DVD specifications for high density read-only disc [HD DVD-ROM (51G)] part 1 physical specifications, version 2.0, took place during the 40^th steering committee meeting on November 15, 2007. Back in September, the DVD Forum also approved version 1.9 specification of 51GB HD DVD media as well as revision 1.0 of triple-layer twin format discs, which can hold up to 30GB of data on its HD DVD side and up to 4.7GB of data on its DVD side.

The new 51GB HD DVD ROM disc has a three-layer structure with each layer storing 17GB of data, which is an advancement in capacity over current ROM discs, which hold 15GB of data in each layer of a single-sided disc. Continued improvement in disc mastering technology has achieved further minimization in the recording pit, supporting a further boost in capacity to 17GB in single layer and a full 51GB on a single-sided triple-layer disc. Toshiba has confirmed the disc structure and its successful operation earlier this year.

Neither Toshiba, nor DVD Forum have confirmed that triple-layer HD DVDs will playback on existing HD DVD hardware, such as players and computer drives. But there are talks in dedicated high-definition related forums that improved 17GB layers actually gained in readability [compared to 15GB layers] and that even first-generation HD DVD players can read tree layers. Therefore, it is highly likely that movies distributed on triple-layer HD DVD 51GB discs will be playable even on the very first HD DVD players.

It remains to be seen whether triple-layer HD DVDs are more cost-efficient compared to dual-layer Blu-ray discs both in terms of media costs as well as replications costs.