high density compact disc (HDCD)

The High Density Compact Disc (HDDC) is a high-performance audio CD. To increase storage capacity, this compact disc (CD) uses a laser that has a wavelength of 670 nm and a numerical aperture of just 0.55.

The shorter wavelength increases the storage capacity many times over that of the audio CD. The higher storage capacity is used for better sound quality, and the sampling depth of 20 bits means that a dynamic range of up to 120 dB can be reproduced.

HDCD is also backwards compatible with the Red Book standard, and a CD or DVD player capable of processing the sound-enhancing information is required to reproduce the full sound quality.