Super Audio CD is a read-only optical audio disc format with high-resolution. It was developed by Sony and Philips Electronics and designed to provide high-resolution audio in both stereo and surround sound modes. In addition to the optional CD-compatible layer using PCM, SACDs also use as audio format called DSD. It is mainly used in the audiophile community.
HD DVD is a redundant high-density optical disc format that was designed for storing data and high-definition video. It was proposed to be the successor to the standard DVD format. However, after the abandonment by Toshiba, the HD DVD Promotion Group was dissolved in 2008.
Also known as High-Definition/Density DVD, it employs a blue laser with a shorter wavelength. This enables it to store about three and a half times as much data per layer as the standard DVD format.
Blu-ray Disc is an optical disc storage medium. Also known as BD or Blu-ray, it was designed to supersede the standard DVD format. The storage medium mainly finds applications in storing high-definition video, PlayStation 3 video games and other data (with 25 GB per single layered and 50 GB per dual layered disc). The standard storage specification for Blu-ray drives is open-ended. These discs have same physical dimensions as standard DVDs and CDs.
DVD-Audio is a digital format designed for delivering high-fidelity audio content on a DVD. It is also known as DVD-A, and isn’t intended to be a video delivery format. The format varies from video DVDs containing concert films or music videos. It offers many possible configurations of audio channels that range from single-channel mono to 5.1-channel surround sound, at different sampling frequencies and sample rates.