Sony today said that it has started shipping 50 GB Blu-ray recordable media in the U.S. The dual-layer discs double the capacity of the single-layer 25 GB media. So far, the 50 GB versions are only available as BD-R write-once discs; Sony said that it will be offering rewritable media (BD-RW) "later this year."

The capacity increase foremost means more storage space for data or movies. However, the new media will be important in for the Blu-ray group in promoting the technology against the competing HD DVD format: The higher capacity will allow movie studios to put more data on a Blu-ray disk to increase the quality of Blu-ray movies. Sony claims that a 50 GB disk can hold four hours of 24 Mb/s video - substantially higher than the VC-1 compressed 15-18 Mb/s the first HD DVD movies and the estimated 10-12 Mb/s currently available Blu-ray movies are using.

The 50 GB media should be available in stores within the next few weeks and will carry a suggested retail price of $48 per disc.