Sony Dynamic Digital Sound

The SDDS logotype

The SDDS logotype

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 35 mm 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.

History

SDDS 8-Channels, this logo is used when all 8 channels are used as opposed to the usual six.

SDDS was developed under contract with Semetex corp. located in Torrance California just a few miles from Sony Studios. Although its key competitors Dolby Digital and DTS had a signficant development lead the SDDS project missed to Dolby Priemr by weeks. Although orginally slated to premier with 'Hook' the SDDS project was delayed a season to become the last of the three digital sound formats to premier, on June 17, 1993 with the Arnold Schwarzenegger film Last Action Hero.

The Code name for the SDDS project was 'Green Lantern', taken from a comic book hero and the old term of 'Magic Lantern' used to discribe the orginal projected pictures. Green came to mind because the key to imprinting the 8 micron data bits was a Green Laser, and of course the Magic of something new on film.

Since then over 1,400 movies have been mixed in Sony Dynamic Digital Sound, and as of early 1999 over 6,750 movie theaters have been equipped with SDDS.

Out of the 1,400 plus films mixed in SDDS, only 97 of them to date have been mixed to support the full 8 channels, mostly because most mixing studios are geared towards producing 5.1 mixes rather than 7.1 mixes. Also the additional sound equipment required for 8 channel SDDS makes it more expensive to install meaning that it only tends to be installed in larger venues.

SDDS was consistently the least popular of the three formats, and Sony Cinema Products, the division responsible for SDDS, closed shop in 2002. SDDS is still supported by most of the major studios, but is not frequently installed in new cinemas anymore. However it is still a very active format, with usage in over 150 new features in 2005 and well over 100 announced for 2006. Of these, only 5 were in 8-channels for 2005, and 4 for 2006.

See also List of 8 channel SDDS films.

Technical

SDDS channel arrangement with 5 front channels, 2 surround channels and a subwoofer channel or "5/2.1".

The SDDS soundtrack is actually printed on with the cyan color layer on the outside edges of the projected film just outside the sprocket holes.

Orginal format used: 8 micron square data bits.

The format carries up to 8 channels of discrete digital sound 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:

• 5 screen channels
  • Left
  • Left center
  • Center
  • Right center
  • Right
• 2 surround channels
  • Left surround
  • Right surround
• Subwoofer channel

Additionally there are 4 backup channels encoded - in case of damage to one side of the film or the other. These are:

• Center
• Subwoofer
• Left + left center
• Right + right center

This gives a total of 12 channels, for which the total datarate is 2.2 megabits per second. This is comparable to the DTS formats bitrate, and far greater than the cinema Dolby Digital bitrate of 0.37 megabits per second.

For additional data security the two sides of the film are separated by 17 frames - so a single splice or series of missing frames will not result in a total loss of data.

External links

• SDDS Official site
• IMDb Sound Mix List