SACD# stands for Super Audio Compact Disc; they are high resolution optical discs developed jointly by Sony and Philips which first became widely available in 1982. The SACD medium supersedes by far the fidelity, storage capacity, dynamic range and stereo imaging capabilities of the standard CD. Its original source may any analog or digital master, but best quality is usually from an audio stream recorded with the Direct Stream Digital (DSD) process, which is also used for the mastering of the distributed SACDs. It is a 1-bit system using a 2.8224 MHz sampling rate, and a dynamic range of 120 dB and frequency range of 20 Hz to 50 kHz. Each SACD can store up to nearly 8 GB of data, and includes both stereo and multichannel DSD options as well as a standard Red Book 44.1K/16-bit CD layer for compatibility with any CD player.
Well over 6000 SACD releases have been published so far, with more than half being European classical music. Jazz and pop SACDs have been mostly remastered versions of previous albums originally recorded on tape. Despite the global decline of CD sales, the sales of SACDs and players increased in 2010. Many inexpensive players are now available which play SACDs as well as CDs, DVDs, and even Blu-ray discs.
DVD-A stands for DVD-Audio, and is a competing hi-res digital format to SACD for delivering high-fidelity audio content on a DVD, though it is different from video DVDs. It was introduced in 2000 and partly has accounted for the lack of SACD gaining a strong position in the consumer market. Instead of using a proprietary 1-bit encoding scheme, DVD-A offers many possible configurations of the audio channels using PCM encoding. They range from 44.1K up to 192K and from 16-bit to 24-bit word length. However, for storing 5.1 channels at 88.2 to 96K resolution, Meridian Lossless Packing (MLP) encoding is also required. Only stereo channels can be accommodated at 192K, though in uncompressed modes, some discs allow a higher rate on the front channels (say 96K/24) and a lower rate (say 48K/15) on the surround channels.
DVD-A discs benefit from the longer playing time of DVDs, not being limited to the 80-minutes of CDs and SACDs. They also allow for either still photos or short videos to be displayed on the screen while listening to the music, as well as lyrics to songs. Most DVD-As also offer a layer that can be played back by any standard DVD player, though at a loss of audio resolution. Although at one time decks that played only DVD-As and CDs were offered, today many universal decks play DVD-As, standard DVDs, SACDs or standard CDs, and some even include Blu-rays. Only a few labels are still producing DVD-As, including AIX Records, Tacet and Classic Records. Software is available which allows the recording of DVD-A discs.