Panasonic Disc Manufacturing of America has added the ability to produce dual-layer Blu-ray Discs to a test production line the company is operating at its factory in California, Panasonic said this week.

The company, which is owned by Japan's Matsushita Electric Industrial, expects to offer its first sample dual-layer discs by the end of December. The capability was made possible by the addition of a dual-layer replication module to an existing line that is currently producing samples of single-layer discs, the company said.

Single-layer Blu-ray Discs have a capacity of 25G bytes and dual layer discs offer 50G bytes. In contrast, an existing dual-layer DVD disc has 8.5G bytes of recording space.

Blu-ray Disc is one of two formats currently engaged in a public relations battle to win the support of movie studios and content producers in a bid to become the de-facto replacement for DVD for high-definition content. The other format is HD-DVD.

The battle is expected to move to the marketplace later this month when Toshiba Corp. is scheduled to launch its first commercial HD-DVD player in Japan. The player is likely to be launched in the U.S. next year. No Blu-ray Disc players are expected to be available in any market until sometime in 2006.

Compared to Blu-ray Disc, the HD-DVD format offers less storage space per disc-layer but is simpler and cheaper to manufacture since it is based on the same basic technology as current DVD.

Disc makers have been reporting for some time that yields -- or the percentage of discs that are good -- on HD-DVD test lines have been over 90 percent while Panasonic said this week that current Blu-ray Disc yields are about 80 percent.

A single-layer HD-DVD disc has 15G bytes of space and a dual-layer disc has 30G bytes of capacity.