Sony Dynamic Digital Sound

File:Sdds.png

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 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 significant development lead the SDDS project missed the Dolby Premier by weeks. Although originally 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 describe the original projected pictures in the late 19th century. 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.

The SDDS chief Architect was Jaye Waas and the Chief Optical engineer was Mark Waring, both employed by Semetex.

The SDDS development took just 11 months from concept to working sound camera but at 16 hours a day 7 days a week in an effort to meet the 'Hook' premier deadline.

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.

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

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.

A photo of a print featuring all four audio formats (or "quad track")- from left to right, SDDS (blue area to the left of the holes), Dolby Digital (grey area between the sprocket holes), analog sound (the two white lines to the right of the Dolby Digital track), and the DTS timecode (the dashed line to the right of the analog track.)

The bulk of major cinema release prints produced in Western countries now simultaneously carry SDDS, DTS, and Dolby Digital data (or "tracks") as well as the traditional two-channel optical sound track. The optical track is required on every print, both because not all cinemas are yet equipped for digital sound, and as a backup in case the digital information fails.

SDDS tracks, due to their placement on the very edges of the film stock, are more prone to damage than the other digital formats. A failure of the digital track results in a "drop-out" to analog sound, which lasts no more than a second or two. A drop-out is audible to most audiences as a change in volume level and a slight loss of fidelity and low-end, although it is more difficult to tell in a properly calibrated auditorium.

Due to the late arrival of SDDS, as well as reliability issues and lack of new equipment, SDDS lags behind Dolby Digital and DTS in deployment. Dolby Digital is included on nearly all releases, and is often the only track on independent or low-budget films. The DTS track is usually included on major releases, although playback requires matching CD-ROMs, which are not always supplied.

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".

Original 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