Telecine Definitions
John Carlson, Chief Colorist at Monaco Video, provides information about film-to-tape transfer sessions
Telecine transfers can be confusing if you are new to the process. The following is a list of terms and definitions describing the identifying information that allows the video and film elements to be matched during post production.
Film Keycode
Information concerning frame location is put on (exposed) by the negative manufacture. This latent image appears after film development, and exists as both human readable numbers (Edge numbers or Key numbers) and as machine-readable numbers (KeyKode™ or Barcode). Keycode is the industry term for any manufacturer machine-readable code. Keycode/edge numbers have 2 letters designating Manufacturer and Film (type) Identifier, plus 6 digits identifying roll number plus 4 digits identifying increments. Keycode/edge numbers also contain a dot to designate the "zero frame". Keycode/edge number increments every foot in 35mm (16 frames). Keycode/edge numbers increment every half foot in 16mm (20 frames).
Video Timecode
Timecode is a digital word that is recorded on the videotape. Timecode can be recorded in two ways, Linear Timecode (LTC) and Vertical Interval Timecode (VITC). The Timecode word is made up of Hours, Minutes, Seconds, Frames and Userbits. Timecode is like a 24-hour clock, after 23:59:59:29 it repeats. Video runs at approximately 30 (29.97) frames per second and film runs at 24 frames per second for projection. The translation of 24 fps to 30 fps is called 2/3 pull down, whereby a frame of film becomes 2 fields of video, and the next frame becomes 3 fields and so on. See the article on Video and Film Pull-down Issues for more information.
The Keycode information from a transfer is encoded into the Userbits. The space available in the Userbit portion of the Timecode word does not allow all of the Keycode information to fit. Footage, frame and pull down are all that are encoded in Userbits. This is a limitation with Linear Timecode (LTC), but not with Vertical Interval Timecode (VITC). Where LTC is a linear channel such as audio and control track, VITC is in the video itself. Lines 11 through 20 are available to store information that is not viewable on normal scan but can be read by decoders. Two-line VITC has been a standard for video since its inception. The two lines contain duplicate Timecode information for protection against drop-outs. By using only these two lines we are still only able to encode footage, frame and pull down. Three-line VITC is a new standard adopted by some transfer facilities on some telecines.
3 Line Format
Line 1: Timecode
Line 2: Keycode including prefix, footage, frames and pull down information
Line 3: Audio Timecode / Production Timecode
With this format, it allows the user a full line of information to encode Keycode. Whereas in two line only a portion of the line was used for Keycode. The Timecode word is still present on line one and the Userbit portion is now free to be used for other purposes such as the lab roll number. The third line is used to encode audio timecode (Nagra) or production Timecode (Aaton/Arri). At this time all this encoding is used as a safety net, or to facilitate window burns of this information into a dub made at a later time.
Window Burns
The information from a transfer can also be put onto the video picture at the time of transfer. Some of the most popular being Timecode, Keycode and Audio Timecode. Others being footage and frame, Acmade, audio roll, lab reel, camera ID, video reel and camera date. Windows can be on throughout the whole transfer or just at the beginning of a scene / take. These pop-up windows contain scene / take information.
Computer Database Files
Computer files can also be created to contain transfer information. The database files are used in non-linear editing systems or in match back programs. These files can contain all the information mentioned above or as little as the start and end of a lab roll. The correlation of Timecode to Keycode is contained within these files, which are used to go from a video edit to film cut.
A film frame can be an "A", "B", "C", or "D" frame when transferred. Files are based on the "A" frame. Because only "A" frames use one Timecode increment. "A" is also the start of the 2/3 sequence, which becomes important when digitizing on a film editor. A Zero "A" frame is when the "A" frame lands on Keycode +00 and Timecode :00. Zero "A" frame is a perferred method but is not a requirement.
