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Timecode is an absolute reference to every frame on a Tape. Without it, Batch Digitize cannot function. There are several different kinds of Timecode, but the most important are SMPTE Timecode and DV Time. DV Timecode DV Timecode is known as DV Time. It always starts at 00:00:00 and is always non-drop frame Timecode. DV Time is carried on the FireWire cable with the video, audio and Device Control. The biggest problem that arises with DV Time is that it resets to zero if the camera operator does not 'hook' to the end of the previously shot footage. If dealing with a miniDV or DVCAM tape with 'broken' Timecode (that is in many parts), either do a clone copy to another DV tape so that the Timecode is created continuously for the entire tape, or name each Timecode section as a different tape. You would need to manually locate the tape in that Timecode 'zone' before Batch Digitize. Clone copies of DV tapes are an exact copy of the original, with no loss of quality. SMPTE Timecode The widespread form of Timecode present on Betacam and digital formats. SMPTE Timecode has provision for presetting the 'hour' which many camera operators use as a Tape number indicator. SMPTE Timecode has provision for User Bits, but these optional User codes are not frequently used and not useful or accessible within Media 100. (Although the Auxiliary Timecode fields in Media 100 could serve a similar function.) There are two standard places for Timecode in video signals, and for NTSC video, there are two formats for the Timecode. Drop vs Non-drop Timecode Because NTSC video runs at 29.97 frames/second, not truly 30 frames/second, the Timecode count of 30 frames a second gradually drifts from real time. An hour of non-drop frame Timecode will be 1 hour 3.6 seconds long. This is an important difference if your program has to exactly fill a timeslot, on a TV show for example. In Media 100 the Timecode type is indicated by a ';' in the 'fields' separator for Drop frame, and a ':' for non-Drop frame. It is important to note that Drop and non-Drop refer only to the Timecode count. No frames are ever dropped from the video. Some frame numbers are dropped during the count, to keep the Timecode count and the clock on the wall, counting together. LTC vs VITC Linear Timecode tracks record on tracks that go straight down the tape, like an audio track on Betacam. These are generally dedicated Timecode tracks. LTC is able to be read at very fast tape speeds down to slow tape speed. It cannot be read when the tape is in pause. LTC can be dubbed independently of the picture and sound on some decks. Vertical Interval Timecode (pronounced "vitsee") incorporates the Timecode in the Vertical Interval of the video signal. VITC reads very accurately in pause, but cannot be read in very high search speeds. VITC is always 'regenerated' when a video edit is done as it forms part of the video signal. Record Run, and Time of Day SMPTE Timecode can be written in two ways. With Record Run, the Timecode counts up whenever the tape is recording. Time of Day, or Free Run, Timecode runs continuously and what is written to the tape is the 'time of day' or whatever point the Free Run Timecode has counted to when recording is started. Free Run or Time of Day is useful for synchronizing Timecode between multiple cameras on the same event. Regardless of when they were recording, the tapes will have the same Timecode in each camera. For all other uses, Record Run is preferred. With either type of Timecode, ensure there is 5-10 seconds of unbroken Timecode before any picture that will be used. This pre-roll time is necessary so the playback deck can accurately locate the desired Timecode. A break during the pre-roll period will confuse Media 100 and abort the Batch Digitize. |
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Please Note: All content in this article is copyright to Philip Hodgetts and Intellligent Assistance, Inc. and is an exclusive excerpt used by permission at Creative Cow. No unauthorized copying is permitted.
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