The time code ( TC ) or time code is a technique used to synchronize various technical devices to within a fraction of a second . It arose out of the need to be able to precisely synchronize sound and image in post-production during film shoots. Nowadays it is used in film and video editing as well as in event technology. In the case of non-linear video editing, you can work without timecode if necessary. B. VHS material is digitized.
The time code is made up of the hour, minute, second and frame (this second) . The number of frames per second (fps) varies depending on the application and technology used:
- in the movie 24 fps
- 48 fps for high frame rate cinema films
- with PAL video format 25 fps
- with the NTSC video format 30 fps
- with high definition video format 50 fps
Event technology usually uses 24 or 30 fps.
With NTSC, the first two frame numbers are usually not assigned in minutes that are not divisible by ten (one starts with hour: minute: 00: 02 instead of hour: minute: 00: 00). For minutes that are divisible by ten, count down from hour: minute: 00: 00. This specialty, called drop frame timecode , takes into account the fact that NTSC does not use exactly 30 fps, but approx. 29.97 fps.
Film and video technology
In order for the various devices to run synchronously, they must be synchronized with so-called mother clocks at the beginning of a day of shooting (only applies to film, not video).
The meaningfulness of time codes is different. At sporting events, raw material recorded by cameras usually has a real time code, which represents the actual time of the recording, other events are recorded starting with 01 as the hour, while a fictitious (mostly standardized) so-called "internal time code" is found on broadcast tapes.
The timecode is recorded in very different ways:
- In modern video cameras, the Vertical Interval Time Code ( VITC ) is used, which is recorded by the rotating head drum like a Hi-Fi track on a VHS machine during helical track recording .
The position of the VITC is in the blanking interval of the image, precisely in the 19th and 21st lines of the 1st field and in the 332nd and 334th lines of the 2nd field (2 fields = 1 frame). The position can be changed in the menu of the machines, but it is recommended not to do this because the time code reader searches for the information in the above locations.
It can be read from the still image to just above normal playback speed. If the machine is used in search mode or as a time-lapse machine, it is switched to the longitudinal time code (LTC), which runs as an additional, linear sound track. This can be read up to the highest speed.
Both time codes can be switched separately on professional machines. The decisive factor for editing, especially with master tapes, is not only the seamless continuity of the time code, but also that LTC and VITC are absolutely synchronous.
Only with the S-VHS or VHS system do you have to consider whether to record the LTC as well, since this system does not have its own LTC track, but then the longitudinal audio track 2, i.e. the right channel, must be used for the hi-fi However, tracks are still available for stereo sound.
- The most common time code in the professional sector is the SMPTE time code . In professional systems, the cassette number can also be encoded. The hour is used for this. 01: 00: 00.00 is the first cartridge, 02: 00: 00.00 is the second, and so on. In the broadcast area, on the other hand, the beginning of a film is often displayed at 10:00 am in accordance with the ARD and ZDF standards.
- Digital VTR devices interleave time code in data packets.
In contrast to the German version, in which the information is stored as binary code between the perforation holes , the French method writes the time code in plain text as image information, which is particularly useful on the cutting table.
The time code is transmitted for copying and editing purposes either as an SMPTE time code signal via an audio cable ( XLR or coaxial ), digitally via a serial interface or, in the case of DV, via FireWire .
If you apply timecode signals to an audio input, you will hear a typical digitally modulated timecode whistle signal, which should not be confused with digital noise.
In event technology, time code is used to be able to control sound and lighting technology as well as moving objects such as trains synchronously. One device, usually the device that plays the music in playback productions, sends the timecode via MIDI cable and transmits it to the control consoles for sound, light and trains. At live concerts, the time code is issued by a separate time dispenser.
An intensive use of time codes takes place at Rammstein , for example , where the light shows, with a few small exceptions, are only "run" using time code.
Further timecodes are the IRIG timecode (IRIG B), which is mainly used in the military sector and on US military test sites for the time synchronization of video and data recording. Also, the NIST a shape of IRIG time code (IRIG H) as the data format for the U.S. time signal transmitter WWV .
Timecode in music
There are also so-called timecode vinyls , which are used to synchronize or control DJ programs using CD, DVD and turntables.
- Alpermann + Velte: Introduction to the basics of the SMPTE / EBU time code ( Memento from June 23, 2012 in the Internet Archive )