In video mastered materials, this can be useful as the video tape can also contain this time code record. We hope that our film systems will someday be able to easily record time code on the film stock. Many experiments and prototype systems are being used currently, but wide spread use of a film recorded timecoded sync system is still in the future. Even in a timecode based system, different time based timecodes can be recorded on the tape. It is important to know what time base was used so that the tape can be properly resolved.
Digital audio is resolved the same way.
Digital data on the tape contains sync bits that are unique and regular. A 60 hz tone is recorded on a dedicated section of the audio tape when it is mastering the audio track. In post production, this 60 hz tone is compared to another 60 hz tone. If there is a difference, this difference becomes an error signal that alters the capstan speed. If the film camera is to be run at speed other an exactly 24.00 fps, we can feed a similarly altered pilot tone to the pilot track on the sound recorder.