HD-DVD (high-density DVD) is an optical digital storage medium with a capacity that far exceeds that of standard DVD media. There are two types. The single-layer HD-DVD offers up to 15 gigabytes (GB) of storage capacity, and the double-layer HD-DVD offers up to 30 GB. A double-layer HD-DVD can contain up to eight hours of 1125-line high-density television (HDTV) programming, or up to 48 hours of standard-definition television programming.