Cinema Product Reviews

Sony Dynamic Digital Sound
Manufacturer:  Sony
Grade:  F
Reviewed November 1999 by Joe Redifer

As if conquering the home electronics market was simply not enough, Sony decided to invade the motion picture product arena with its inferior designs and questionable reliability by introducing its very own digital sound format -- Sony Dynamic Digital Sound -- SDDS for short.

SDDS works by placing the digital data on both sides of the film on the outer edge, outside of the sprocket holes.  The outer edge of the film is the part that touches all rollers and is the most volatile place to put a digital track.  SDDS tracks are not known for their longevity.  A vast array of constantly failing LEDs reside in the reader that sends the data to the decoder which also duplicates the function of whatever cinema processor you happen to be using (thus raising the price for SDDS) and also overrides it.  SDDS features its very own B-chain, or equalization.  Many technicians swear that the pink noise inside the SDDS decoder is better and easier to EQ than any typical cinema processor.  Is Japanese pink noise better than American pink noise?  I guess not, since there isn't an actual SDDS pink noise test film.  Why not?  From everything that I have heard, SDDS cannot reproduce pink noise (all frequencies) from the digital data on film.

SDDS uses ATRAC (Adaptive Transform Acoustical Coding) compression at a ratio of about 5:1.  This compares favorably with Dolby Digital's 12:1 AC-3 compression, but it is loses more than DTS's 4:1 compression.  I don't know how Dolby does it, but even at 12:1 compression, SRD tracks still sound a lot better than SDDS.  To my ears, SDDS lacks fullness and just seems rather hollow.  It is interesting to note, however, that MiniDiscs also use ATRAC compression, but for some reason MiniDisc sounds just fine and dandy.  Perhaps the cinema version of ATRAC is somewhat "special"?

SDDS has 8 full range channels and a few back up (lower sampling rate quality) channels.  Both DTS and Dolby Digital have 5 full range channels, but Dolby has an extra 1/10th of a channel dedicated to the sub (DTS derives its subwoofer information from the surround channels).  Most movies are mixed for 5.1 channels nowadays.  Sound mixers tend to prefer using this same mix for SDDS, resulting in 2 completely wasted channels.  There are about 2 or 3 movies a year that are released in true 8 channel sound.  I have actually seen a few of those in a true 8 channel theatre.  Does it make a difference?  Certainly not one that I can tell, and I listen for those types of things.  Actually, nobody I personally know has stated they can tell more than a small difference between a 6 and 8 channel mix.

Performance.  Does SDDS perform?  Sometimes.  But quite often an LED or two goes bad inside the reader, resulting in constant dropouts either to silence or to the backup digital tracks, which are definitely worse than the analog stereo tracks.  Sometimes the sensor on the back of the toothed sprocket on the reader will get a piece of dust in it, and it will not turn on the LEDs enough to see all of the information, and the result is the same.  I have seen instances when the decoder will stop working on a busy Saturday night for absolutely no reason, only to work fine the next day.  I have heard more horror stories about SDDS than I ever care to.  Technicians seem to love it since they get a laptop computer from their higher ups to calibrate them.  But ask just about any projectionist who has worked extensively with SDDS and they will tell you that it pretty much sucks.

The final nail in Sony's coffin (besides the super high price) is that they no longer offer SDDS without the built in analog cinema processor.  You cannot buy a unit and hook it up to run with a Dolby CP65 (or whatever).  You MUST use Sony's processor.  It does not sound very good.  I guess Sony wants to conquer the analog cinema processor market as well.  SDDS is a rather idiotic solution for digital sound.  Both DTS and Dolby Digital sound far better and are far, far more reliable.  And isn't that what it's about?

-Joe Redifer
Sony can be contacted at

Joe Redifer has been a projectionist for the last few years.  He learned at Mann Kipling, went on to the UA Greenwood and finally spent 2 years at Mann Chinese.  At the Chinese, Joe performed most of the daily maintenance on the equipment.  Joe is not a technician and has no test equipment, but is an experienced projectionist.  These reviews are representative of the performance of the equipment/services from his perspective.

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