SDDS

The Third Format in the ’90s Sound Wars

SDDS was the third major digital audio format to enter the cinema market in the early 1990s, positioned as a competitor to Dolby Digital and DTS. Developed by Sony Cinema Products Corporation, it debuted in 1993 on the film Last Action Hero. SDDS was heavily supported by Sony’s own cinema hardware division and its film studios, Columbia Pictures and TriStar Pictures, but it struggled to achieve the same widespread adoption as its rivals.

Technical Innovation: Eight Channels and Redundancy

SDDS had two key technical differentiators:

1. Eight-Channel Audio: While Dolby and DTS were initially 5.1 channel systems (Left, Center, Right, Left Surround, Right Surround, Subwoofer), SDDS supported up to 7.1 channels. Uniquely, it added two extra channels behind the screen, for a total of five screen channels: Left, Left-Center, Center, Right-Center, and Right. The goal of these additional ‘inner’ screen channels was to create a smoother and more seamless soundstage, allowing for more precise panning of dialogue and effects across the large cinema screen.
2. Redundant Data Tracks: The SDDS audio data was optically printed onto the 35mm film in two cyan-colored strips that ran along the outer edges, outside the sprocket holes. These two tracks were redundant copies of each other. This was a key selling point for reliability; if one side of the film print was scratched or damaged, the other side could still be read, preventing a total loss of audio.

A Format Lost to Time

Despite its technical merits, SDDS remained the least-used of the three formats. The need for special five-channel speaker systems behind the screen made it a more expensive upgrade for theaters. With the industry-wide transition to digital cinema packages (DCPs), which have their own standardized audio formats, the need for proprietary film-based systems like SDDS vanished. It is now considered a legacy technology from the final era of 35mm film exhibition.