What is timecode or TC?

A timecode is a sequence of numeric codes generated at regular intervals by a timing synchronization system. They provide a time reference for editing, synchronization, identification and transcription. In video production and filmmaking, SMPTE (Society of Motion Picture and Television Engineers) timecode is a form of media metadata (along with subtitles and closed captioning) used extensively for synchronization, logging and identifying material in recorded media.  Timecodes are added to film, video or audio material and have also been adapted to synchronize music. Linear and vertical-interval timecodes were developed in 1967 by EECO, an electronics company that developed video recorders and later video production systems. EECO assigned its intellectual property to permit public use.

The SMPTE family of timecodes are used in film, video and audio production, and can be encoded in many different formats, including linear timecode (LTC), vertical interval timecode (VITC), AES-EBU embedded timecode used with digital audio, burnt-in timecode, control track timecode (CTL) and MIDI timecode. Timecodes for purposes other than video and audio production include inter-range instrumentation group timecode (IRIG), which is used for military, governmental and commercial purposes.

During filmmaking or video production shoot, the camera assistant will typically log the start and end timecodes of shots, and the data generated will be sent on to the editorial department for use in referencing those shots. This shot-logging process is typically done using shot-logging software running on a laptop computer that is connected to the timecode generator or the camera itself.

Linear timecode (LTC) is suitable to be recorded on an audio channel, or by audio wires. This is how it is distributed within a studio to synchronize recorders and cameras. To read LTC, the recording must be moving, meaning that LTC is nonfunctional when the recording is stationary or nearly stationary. This shortcoming led to the development of VITC (vertical interval timecode). VITC is recorded directly into the VBI (vertical blanking interval) of the video signal on each frame of video. The advantage of VITC is that, since it is a part of the playback video, it can be read when the tape is stationary.

CTL timecode is SMPTE timecode embedded in a videotape’s control track. Burnt-in timecode (BITC) is a timecode in which the numbers are burnt into the video image so the timecode can be easily read. Videotapes that are duplicated with these timecode numbers burnt in to the video are known as window dubs.