Left: Detail of CDS Digital soundtrack, looking a bit like a piece of styrofoam.
The Cinema Digital System was developed by Eastman Kodak and the Optical Radiation Corporation. It was the film industry's first foray into discrete multi-channel digital sound and was used in eight films during 1990-1991. It was first used on 70mm blowups of "Dick Tracy", an inauspicious beginning. Next was the 70mm blowups of Days of Thunder. Frames from that film are shown above.
To put it mildly, CDS bombed. The primary reason seems to be the fact that there was no analog soundtrack as a backup in the event of a failure of the digital system. Probably economics played a role as well, and the timing just wasn't right. Initially the system was used on only 70mm prints but a 35mm system was developed and 70mm blowups virtually were eliminated. That much runs parallel with the history of the later digital systems offered by Dolby SR-D, Digital Theatre Systems, and Sony Dynamic Digital System.
Below is a frame from The Doors, released in 1991 as the first 35mm CDS film.
Like its 70mm counterpart, the 35mm version neglected to carry an analog soundtrack as a failsafe backup or compatibility with all 35mm projection equipment. Readers that don't like their images squeezed may scroll down to see how the picture looked in a theatre.