Various Types of Optical Disc Formats

Also known as: High-Definition DVD, Advanced Optical Disc (AOD)

Description: HD-DVD, or High-Definition DVD, is a next generation optical disc format designed to store high-definition video. The regular DVD format was developed before the advent of high-definition television standards. HD-DVDs have more storage capacity than regular DVDs and generally use more efficient compression. The improvements in technology mean that more data can be sent to an HDTV faster when using HD-DVD as opposed to regular DVD, which translates to a television picture with more detail.

Toshiba and NEC are the original developers of the HD-DVD standard, which is in competition with the Blu-ray format.

Facts: The maximum storage capacity of an HD-DVD is 30 gigabytes.

Description: Blu-ray disc is an optical disc format designed to store high definition video and high density data. Its per layer capacity is 25 Gigabytes. The name is derived from the format's use of blue-violet laser light that allows for significantly more data density than can be achieved on a DVD even though the physical dimensions are the same.

Also known as: Digital Video Discs, Digital Versatile Discs

Description: The DVD format was finalized in 1996. DVDs are optical discs with a larger capacity than CDs that are used to store video, audio, games, and other data in digital format. Single layer DVDs store 4.7 gigabytes of data and dual layer DVDs store 8.5 gigabytes of data.

Also known as: CD

Description: First introduced as audio discs in 1980, the format was expanded in 1984 to include data storage (the CD-ROM). Their capacity is up to 700 megabytes of data or 80 minutes of high quality audio. The CD-R is a version of the CD that is recordable by home users. The CD-R became available in 1990. Prior to that time, CDs were only made commercially in large batches.

In 1997, the CD-RW, or Compact Disc ReWritable, was introduced. This type of disc contains a phase-alloy recording layer. Normally this layer is crystallized (organized in a regular pattern), but the laser in a CD writing disc drive is used to selectively melt this layer into an amorphous (or disorganized) state. When rewriting, using the laser on the same spot at a lower intensity anneals the layer back to a crystalline state. The difference in reflectance between the crystalline and amorphous portions of the medium define the digital data.

Standard CD sizes are 21 minutes, 63 minutes, 74 minutes, or 80 minutes.