China Blue High-definition Disc China Blue High-definition Disc China Blue High-Definition (CBHD; ; alternatively "China High Definition DVD") is a high definition optical disc format announced in September 2007 by the Optical Memory National Engineering Research Center (OMNERC) of Tsinghua University in China. The format is a derivative of the HD DVD, a medium created by the DVD Forum designed to succeed regular DVDs. Although HD DVD was scrapped as a result of losing the format war to Blu-ray, CBHDs continued to be produced and marketed, though only in China. Originally called CH-DVD, CBHD is a joint venture between the DVD Forum and OMNERC.
Optical disc rotation (Constant linear velocity (CLV), Constant angular velocity (CAV), or zoned-CAV), the composition of lands and pits, and how much margin is unused is at the center and the edge of the disc. Second-generation optical discs were for storing great amounts of data, including broadcast-quality digital video. Such discs usually are read with a visible-light laser (usually red); the shorter wavelength and greater numerical aperture allow a narrower light beam, permitting smaller pits and lands in the disc. In the DVD format, this allows 4.7 GB storage on a standard 12 cm, single-sided, single-layer disc; alternatively, smaller media, such as