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.
SACD resemble a standard compact disc in terms of physical dimensions, while their density is same as that of a DVD. They encode audio using a process known as Direct Stream Digital. The sampling rate of SACD is 2822.4 kHz and the resolution is one bit. SACD stereo recordings can stream data at an uncompressed rate of 5.6 Mbps. These recordings have a wider frequency and dynamic range when compared to the conventional CDs. SACD is of three types.
- Hybrid – These discs include a Red Book layer that is compatible with most of the Compact Disc players, and a 4.7 GB SACD layer.
- Single-layer – These discs include a 4.7 GB HD layer with no CD layer and are physically a DVD-5 DVD.
- Dual-layer – These include two HD layers totaling 8.5 GB with no CD layer and are physically a DVD-9 DVD. They enable the storage of twice as much data but eliminate CD player compatibility. For this reason, they are rarely used.
The commercially released SACDs have both stereo and surround mixes included. The CD layer confers backward compatibility but isn’t required. When the CD layer is omitted, the SACD needn’t be limited to an 80-minute playing time. The playing time can be extended to four hours or more for stereo when the CD layer is omitted.