SDDS stands for Sony Dynamic Digital Sound, which is a cinema sound system developed by Sony. Digital sound information is recorded on both outer edges of the 35mm film release print. The system supports up to 8 independent channels of sound: 5 front channels, 2 surround channels and a sub-bass channel. This arrangement is similar to 70 mm magnetic sound formats - and is useful mainly for very large cinema screens. Smaller cinemas normally only have 3 screen channels - in which case the soundtrack is downmixed. SDDS is not currently available on any home format.