Cracking the Video Time Code (page 2)

SMPTE, LTC and VITC: who cares, right? How does all this time code make life easier? Using time code is a great way to organize productions during shooting and editing.

Your camcorder writes time code (i.e. a time-stamp) in an hours:minutes:seconds:frames format (HH:MM:SS:FF). Video time code signals use a 24-hour counting standard. Therefore, every video frame on a tape is time-stamped with a value ranging between 00:00:00:00 and 23:59:59:29.

Some video systems used to confuse a zero starting point with the absence of any time code at all. Another problem with 00:00:00:00 is that some projects and gear require a pre-roll. Rewinding before zero gives you negative time code, which is not handled well by some systems.

The time-stamp is an ideal logging device when shooting video. For example, a videographer shooting a sporting event notes the time of an important play. By logging the time of the play, the tape's time code can be used to determine the exact location of the shot, rather than having to search through hours of video to find it.

Some gear allows you to choose between shooting in real time or control time. Real time means that you'll see the time as it appears on a standard clock. Control time displays a view of the actual position of the footage on the tape.

Time code also offers the ability to synchronize multiple machines, including editing decks. The unique time-stamp allows editing machines such as switchers and dubbers to run in perfect synchronization. However, some of the control protocols for consumer editing decks do not use time codes that time-stamp every frame. These decks limit the overall accuracy of editing using the time-stamp.

One of the ways that time code is regulated between synchronized equipment is through a Serial Digital Interface (SDI) connection. SDI is the standard digital video transport method used by professional and broadcast equipment and is another technical standard maintained by SMPTE.

One of the most critical problems involving time code is discontinuity, sometimes referred to as broken time code. Broken time code happens when the camera cannot find existing time code on the tape and resets the counter to zero. This can happen when you start a new tape or when you start recording after some pre-existing footage to a blank section of the tape.

One way to prevent breaks in time code is to pre-black your tapes. To do this, insert your tape and record with the lens cap on (and, optionally, the audio muted). Record throughout the entire length of the tape to ensure that every video frame has time code on it.

Blacking tape is a preventative measure that's good when re-using old tapes and is critical when working with older analog cameras that support time code. Nowadays, however, many digital cameras are equipped with features that help eliminate broken time code, for example an end-search feature, which allows you to find the last recorded frame on a tape.

With time code, logging, synchronizing and managing footage becomes a simpler task. By understanding how it relates to shooting and editing, videographers gain an advantage during their project's production.

Pat Bailey is a digital video Technical Support Analyst and freelance writer.

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