… for Codecs & Media
Tip #830: Count the Timecode Formats
Timecode takes many forms, all with the goal of clearly labeling every frame of video.
Most of us are familiar with timecode: A unique label for each frame of video in a clip, expressed as four pairs of numbers: Hours:Minutes:Seconds:Frames (or milliseconds, depending upon format).
While timecode expresses these locations as time values, there is no necessary relationship between timecode and the time of day the image was recorded. Sometimes there is, but it isn’t required.
Thinking about timecode got me wondering about how many different timecode formats there are. And that took me to Wikipedia.
In video production and filmmaking, Wikipedia writes, SMPTE timecode is used extensively for synchronization, and for logging and identifying material in recorded media. 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 was traditionally done by hand using pen and paper, but is now typically done using shot-logging software running on a laptop computer that is connected to the time code generator or the camera itself.
The SMPTE family of timecodes are almost universally used in film, video and audio production, and can be encoded in many different formats, including:
- Linear timecode (LTC), in a separate audio track
- Vertical interval timecode (VITC), in the vertical blanking interval of a video track
- AES-EBU embedded timecode used with digital audio
- Burnt-in timecode, in human-readable form in the video itself
- CTL timecode (control track)
- MIDI timecode
Keycode, while not a timecode, is used to identify specific film frames in film post-production that uses physical film stock. Keycode data is normally used in conjunction with SMPTE time code.
NOTE: Rewritable consumer timecode is a proprietary consumer video timecode system that is not frame-accurate, and is therefore not used in professional post-production.
All these different timecode formats provide one key reason why we need to copy all files from a camera card to our hard disk. Many times, timecode is not embedded in the video.
Also, aside from BWAV (Broadcast WAV) files, audio does not support timecode.
Here’s a Wikipedia article to learn more.