title: Optical audio disc
text: An audio optical disc is an optical disc that stores sound information such as music or speech.
  
  It may specifically refer to:
  
  Audio CDs
   Compact disc (CD), an optical disc used to store digital data (700 MB storage)
   Compact Disc Digital Audio (CD-DA), a CD that contains PCM encoded digital audio in the original "Red Book" CD-DA format
   5.1 Music Disc, an extension to the Red Book standard that uses DTS Coherent Acoustics 5.1 surround sound
   Compressed audio optical disc, an optical disc storing MP3s and other compressed audio files as data, rather than in the Red Book format
  
  Audio DVDs
  DVD, 4 GB single layer, 8 GB double layer storage
   DVD-Audio, a DVD that plays audio
   Super Audio CD (SACD), a format which competes with DVD-Audio
  
  Audio Blu-rays
  Blu-ray, 25 GB single layer, 50 GB double layer
   BD-Audio, a Blu-ray disc that is capable of audio-only playback
  
  See also
  CD-4 or Compatible discrete four-channel sound, a variety of quadrophonic audio for vinyl records