Time code generated in file-based recorders is fundamentally different than time code on a tape recorder. Whereas a tape recorder has a continuous time code reference for each location on the tape, a (broadcast wave) audio file only has a single time code value—from which all time code values are calculated.
Chiefly because of this difference time code numbers on one file may be a duplicate of time code numbers from another audio file under the right circumstances. With a time code overlap, audio too can overlap from file to file.
The circumstances where file overlapping can occur are limited. An example of a situation where overlapping code can exist is when:
- a camera is set to rec-run time code mode,
- a 702T, 744T, or 788T is receiving time code from the camera via RF link or hardwired and is set to external time code mode,
- audio is manually "rolled" before picture, and
- audio is manually stopped after picture.
Looking at the screen shot above (Vegas 6 using its broadcast wave import function), each take from the camera is butted up to the next take, as expected in rec run. There are no gaps in the camera's audio file or in the time code numbers.
Each audio take is shown on a separate track for illustration purposes. Because the audio recorder was started before the camera started, its time code numbers reflect its actual starting time so that audio is in sync with its corresponding picture. Each audio take matches up perfectly with the camera. The consequence of audio starting before picture and stopping after picture is where the overlap occurs. Both time code and audio overlap each other. This is normal and proper behavior by the audio recorder. Make certain to notify your post-production supervisor if this situation is going to be encountered so they can accommodate for it in their workflow. Trimming the heads and tails of the audio files to match the picture will be required.