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.
However, in a joint effort over a three-year period, and with a $5 million total investment, Kodak developed a special fine-grained, high-resolution negative film capable of holding more information than previous films and Optical Radiation Corporation developed a special audio coding and error correction system, resulting in the Cinema Digital Sound system.
The third data channel, an identification track, could be used to record a variety of user-defined parameters specific to the film (such as curtain opening/closing, seat movement or lighting effects.)
As the CDS system was available for only two years before its complete withdrawal from the market, no use of the SMPTE time code or MIDI channels was ever implemented.
Just as in audio tape machines, transport problems with tension, guides, and supply and take-up reels could result in vertical or horizontal weave, and as bit sizes were only 14μm, precise timing and tracking was essential, thus the CDS system required installation of special projector modifications to smooth the film path travel and steady the take-up speed.
Horizontal tracking was provided by a 76-MHz digital servo, while vertical timing was accomplished with an algorithm written into the data format itself.