CTL timecode
Encyclopedia
CTL timecode, developed by JVC
in the early 1990s, is a unique technique for embedding, or striping, reference SMPTE timecode onto a videotape.
Similar to the way VITC timecode is embedded in the vertical interval area of a video signal, CTL timecode embeds SMPTE timecode in the control track
area of helical scan
video recordings. The advantage of both VITC and CTL timecode is that a precious audio track does not have to be sacrificed for linear timecode
.
Though a very effective technology, and still probably in limited use today, CTL timecode never really caught on. JVC is apparently the only manufacturer that included CTL timecode capability in their video products, and this was limited to select professional S-VHS
equipment.
When it was introduced, there was a lot of undeserved negativity about CTL timecode, because people misunderstood how it worked. Many incorrectly assumed that CTL timecode was nothing more than a control track pulse signal. The only real problem with CTL timecode was that JVC chose to call it "CTL timecode".
Control Track Pulse: Most are familiar with the digital "counters" on VHS recorders and camcorders, viewed via the onscreen display (OSD) and/or a dedicated LED display. These numbers are sometimes in real time format (hours:minutes:seconds), but are often only an ambiguous 4 digit sequential counter. These numbers advance up or down based on the machine counting a tape's control track pulses. This type of display is useful only as a simple and temporary reference, as it is very inaccurate, and the counter is reset to zero when a tape is inserted. A basic 4 digit counter is almost completely worthless, as their rate of advance was never standardized by manufacturers.
Conversely, CTL timecode is an absolute timecode with specific digital references for every frame of video. Thus, a tape with CTL timecode can always display current timecode position accurately, even if the tape is moved from one machine to another. CTL timecode embedding can be transferred when making a copy, as long as the recording machine supports CTL timecode. Because CTL timecode is SMPTE timecode, its timecode can be interchanged with other SMPTE timecode schemes, like VITC and LTC (linear, audio track) timecode, as well as SMPTE timecode devices like timecode readers, generators, window dub inserters, MIDI synchronizers, and edit controllers.
CTL timecode is vulnerable to any gaps or problems in a tape's control track, but so is LTC and VITC timecode. The acronym LOCT , used by many video professionals, can mean "Loss Of Control Track", and/or "Loss Of Continuous Timecode".
JVC
, usually referred to as JVC, is a Japanese international consumer and professional electronics corporation based in Yokohama, Japan which was founded in 1927...
in the early 1990s, is a unique technique for embedding, or striping, reference SMPTE timecode onto a videotape.
Similar to the way VITC timecode is embedded in the vertical interval area of a video signal, CTL timecode embeds SMPTE timecode in the control track
Control track
A control track is a track that runs along an outside edge of a standard analog videotape . The control track encodes a series of pulses, each pulse corresponding to the beginning of each frame. This allows the video tape player to synchronize its scan speed and tape speed to the speed of the...
area of helical scan
Helical scan
Helical scan is a method of recording high bandwidth signals onto magnetic tape. It is used in reel-to-reel video tape recorders, video cassette recorders, digital audio tape recorders, and some computer tape drives....
video recordings. The advantage of both VITC and CTL timecode is that a precious audio track does not have to be sacrificed for linear timecode
Linear timecode
Linear Timecode is an encoding of SMPTE timecode data in an audio signal, as defined in SMPTE 12M specification. The audio signal is commonly recorded on a VTR track or other storage media. The bits are encoded using the biphase mark code, also known as "FM": a zero bit has a single transition...
.
Though a very effective technology, and still probably in limited use today, CTL timecode never really caught on. JVC is apparently the only manufacturer that included CTL timecode capability in their video products, and this was limited to select professional S-VHS
S-VHS
S-VHS is an improved version of the VHS standard for consumer-level analog recording videocassettes. It was introduced by JVC in Japan in April 1987 with the HR-S7000 VCR and certain overseas markets soon afterwards...
equipment.
When it was introduced, there was a lot of undeserved negativity about CTL timecode, because people misunderstood how it worked. Many incorrectly assumed that CTL timecode was nothing more than a control track pulse signal. The only real problem with CTL timecode was that JVC chose to call it "CTL timecode".
Control Track Pulse: Most are familiar with the digital "counters" on VHS recorders and camcorders, viewed via the onscreen display (OSD) and/or a dedicated LED display. These numbers are sometimes in real time format (hours:minutes:seconds), but are often only an ambiguous 4 digit sequential counter. These numbers advance up or down based on the machine counting a tape's control track pulses. This type of display is useful only as a simple and temporary reference, as it is very inaccurate, and the counter is reset to zero when a tape is inserted. A basic 4 digit counter is almost completely worthless, as their rate of advance was never standardized by manufacturers.
Conversely, CTL timecode is an absolute timecode with specific digital references for every frame of video. Thus, a tape with CTL timecode can always display current timecode position accurately, even if the tape is moved from one machine to another. CTL timecode embedding can be transferred when making a copy, as long as the recording machine supports CTL timecode. Because CTL timecode is SMPTE timecode, its timecode can be interchanged with other SMPTE timecode schemes, like VITC and LTC (linear, audio track) timecode, as well as SMPTE timecode devices like timecode readers, generators, window dub inserters, MIDI synchronizers, and edit controllers.
CTL timecode is vulnerable to any gaps or problems in a tape's control track, but so is LTC and VITC timecode. The acronym LOCT , used by many video professionals, can mean "Loss Of Control Track", and/or "Loss Of Continuous Timecode".
See also
- control trackControl trackA control track is a track that runs along an outside edge of a standard analog videotape . The control track encodes a series of pulses, each pulse corresponding to the beginning of each frame. This allows the video tape player to synchronize its scan speed and tape speed to the speed of the...
- Linear timecodeLinear timecodeLinear Timecode is an encoding of SMPTE timecode data in an audio signal, as defined in SMPTE 12M specification. The audio signal is commonly recorded on a VTR track or other storage media. The bits are encoded using the biphase mark code, also known as "FM": a zero bit has a single transition...
- Vertical interval timecodeVertical interval timecodeVertical Interval TimeCode is a form of SMPTE timecode embedded as a pair of black-and-white bars in a video signal. These lines are typically inserted into the vertical blanking interval of the video signal...
- Burnt-in timecodeBurnt-in timecodeBurnt-in timecode is a human-readable on-screen version of the timecode information for a piece of material superimposed on a video image...
- MIDI timecodeMIDI timecodeMIDI time code , or MIDI time division, embeds the same timing information as standard SMPTE timecode as a series of small 'quarter-frame' MIDI messages. There is no provision for the user bits in the standard MIDI time code messages, and SysEx messages are used to carry this information instead...
- AES-EBU embedded timecode
- Rewritable consumer timecodeRewritable consumer timecodeThe Rewriteable Consumer Timecode is a nearly frame accurate timecode method developed by Sony for 8mm and Hi8 analog tape formats. The RC timecode is written by the video camera directly to analog tape tracks and records the hour, minute, second and frame for each frame of video recorded to tape...