Pioneer claims to have developed read-only disc media with 16 layers offering a total capacity of 400 GB.
While the 25 GB per-layer capacity is equivalent to what Blu-ray provides, Pioneer did not say which technology its new discs are based upon and did not even mention whether blue laser or red laser technologies were employed.

Pioneer's announcement said "it is possible to maintain compatibility" between the new, very high-density Blu-ray format and existing players. However, the company indicated that some kind of modification may be necessary, either in the production of the discs or in the players.

The key to making such storage possible, Pioneer said, is reducing interference between adjacent layers, as its prototype does.

Currently the technology is read-only, but Pioneer has indicated that a writable version is being developed.
Assuming the technology is based on Blu-ray, 400 GB disc could accommodate 48 hours of high-definition video.
Sony previously noted that Blu-ray could be scalable to up to eight to ten layers or 200 to 250 GB.

A formal announcement of the 400GB technology is expected at the International Symposium on Optical Memory and Optical Data Storage, which begins Sunday in Hawaii. Industry observers anticipate that Pioneer will not commercially produce the discs, but will work with manufacturers. TDK has also announced a high-capacity disc, with six layers and a 150GB capacity.

The multi-layer disc technology was used by New Medium Enterprises, developer of the red-laser based High Definition Versatile Multilayer Disc (HD VMD). Expanding on the DVD specifications, its 4-layer disc offers in excess of 20GB. The company’s technological roadmap called for up to 20-layer discs, and could be transitioned to blue-laser technology. The company patented very efficient P2 processes to separate layers.

Story filed 10.07.08