12 Recording Timecode
Timecode is essentially a numbering system which is stored as ‘Metadata’ within each frame of video (metadata is information that describes features of the content). Each frame is represented in Hours, Minutes, Seconds and Frames (00:00:00:00). The purpose of timecode is to give each frame of recorded material a unique reference for logging, identification, synchronisation and editing of video and audio recordings.
SMPTE (Society of Motion Picture and Television Engineers) timecode is a set of specifications and format of timecode. The two main methods of recording SMPTE (pronounced “simp-tee”) timecode in use today are LTC (pronounced “vit-see”, an abbreviation of Linear or Longitudinal Timecode) and VITC (pronounced “vit-see”, an abbreviation of Vertical Interval Timecode). LTC timecode is recorded on an audio track in a linear fashion, whilst VITC timecode is recorded within the video vertical blanking interval of the video signal.
Most professional cameras and VCRs will give the operator the choice of two main modes of recording timecode – ‘Record Run’ and ‘Free Run’. Each of these modes has its benefits.
Record Run mode will give you a progressive and sequential timecode on your recorded material and will enable you to more easily monitor the duration of material you have recorded. However, if your camera is powered down and then switched on again, and recording immediately commenced, the timecode may not restart sequentially as the camera might be unable to line up exactly with the last recorded frame. To overcome this, and the other problems which can be caused by having breaks in the recording, many cameras have what is referred to as a ‘RET’ (Return) button. This will cue the tape up with the last recorded frame and set it in Pause/Record mode. This will then ensure a continuous timecode recording.
Free Run mode is useful if you want to note the actual time of day when that segment of recording was taken. This can be particularly useful when you are using more than one camera to record material and later need to synchronise the recordings from each camera. In this instance, the timecode on each camera must be simultaneously reset so that they are all producing the same continuous timecode from that point. This can be done manually, or automatically if the cameras have the facility to connect timecode outputs with each other. The drawback of this mode is that the resultant timecode may have large gaps as the recording was stopped and then started again. This can confuse editing systems, especially if your post production edits span across numerous Free Run timecode segments or, indeed, if the filming extends over more than a 24-hour period.
Whilst timecode records hours, minutes, seconds and frames, you can also add additional information called ‘User Bits’ to the metadata. This is enables the videographer to add a limited amount of additional information alongside the timecode for easier identification of the recorded material. For instance, in a multiple camera situation each camera could have its own unique, user- entered identity number within the metadata so that each camera can be identified during post production.
Whilst timecode is referred to as ‘off-screen’ information (in that it is not normally displayed as part of the picture), most professional playback devices enable the timecode to be displayed if required. This process is called ‘Burnt-In Timecode’ (or BITC – pronounced “bit-see”), and is commonly used for providing customers with a copy of the edited material (called a ‘Preview Copy’), so that they can identify and comment on specific frames or time ranges, from which the editor can then accurately relate to the original edit or master.