Sony Dynamic Digital Sound
Sony Dynamic Digital Sound (Japanese: ソニー・ダイナミック・デジタル・サウンド, Hepburn: Sonī Dainamikku Dejitaru Saundo, SDDS) is a cinema sound system developed by Sony, in which compressed digital sound information is recorded on both outer edges of the 35 mm film release print. The system supports up to eight independent channels of sound: five front channels, two surround channels and a single sub-bass channel. The eight channel arrangement is similar to large format film magnetic sound formats such as Cinerama and Cinemiracle. The five front channels are useful for very large cinema auditoriums where the angular distance between center and left/right channels may be considerable. SDDS decoders provide the ability to downmix to fewer channels if required.
"SDDS" redirects here. For IMF reporting guidelines, see Special Data Dissemination Standard.Abbreviation
The format carries up to 8 channels of Dynamic Digital Sound (DDS) encoded using Sony's ATRAC codec with a compression ratio of about 5:1 and a sampling rate of 44.1 kHz. The channels are:
Additionally there are 4 backup channels encoded – in case of damage to one side of the film or the other. These are:
This gives a total of 12 channels, for which the total bitrate of 2.2 megabits per second. This is more than the maximum 1.536 megabits per second DTS format bitrate, and far greater than the cinema Dolby Digital bitrate of 0.64 megabits per second.
For additional data reliability the two sides of the film are separated by 17 frames and half, so a single splice or series of missing frames will not result in a total loss of data.
Decoder[edit]
The SDDS decoder is installed in the sound equipment rack. The decoder receives the information from the reader and translates it into audio signals routed to the cinema's power amplifiers. The decoder is responsible for a series of processes that must be performed before the audio is recovered. Next, errors caused by scratches or damage to the film are corrected using redundant error recovery data. Since SDDS is read at the top of the projector, the data is delayed slightly to restore synchronization with the picture. And finally, adjustments in tonal balance and playback level are made to match the specific auditorium's sound system and acoustics. SDDS is designed to process sound entirely in the digital domain, bypassing any existing analog processor, preserving clarity and providing full dynamic range.