Optical Radiation Corporation

Optical Radiation Corporation

Cinema Digital Sound (CDS) is a multi-channel surround sound format used for theatrical films in the early 1990s. The system was developed by Eastman Kodak and Optical Radiation Corporation. CDS was quickly superseded by Digital Theatre System (DTS) and Dolby Digital formats.

CDS format replaced the analogue audio tracks on 35mm and 70mm prints with 5.1 discrete audio. The 5.1 tracks were encoded using 16-bit PCM audio in a delta modulation compression which resulted in a compression level of 4:1. The audio channels in CDS were arranged in the same way that most current 5.1 systems with Left, Center, Right, Left Surround, Right Surround and LFE. Not all films with CDS soundtracks used all 5.1 channels with some, such as Edward Scissorhands, using only the 4 channels that were supported by Dolby Stereo. Universal Soldier was the last film encoded with CDS.

The digital information was printed on the film, similar to Dolby Digital and SDDS. However, unlike those formats, there was no analog optical backup in 35mm and no magnetic backup in 70mm, meaning that if the digital information were damaged in some way, there would be no sound at all. This was one of the factors that contributed to its inevitable demise; the then-new Dolby Digital format moved its information to another area (in between the film sprocket holes), preserving the optical tracks.