In a
video tape recorder
A video tape recorder (VTR) is a tape recorder designed to record and playback video and audio signal, audio material from magnetic tape. The early VTRs were open-reel devices that record on individual reels of 2-inch-wide (5.08 cm) tape. ...
, tracking is a calibration adjustment which ensures that the spinning playback
head
A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple ani ...
is properly aligned with the
helical scan
Helical scan is a method of recording high-frequency signals on magnetic tape, used in open-reel video tape recorders, video cassette recorders, digital audio tape recorders, and some computer tape drives.
With this technique, magnetic tape he ...
signal written onto the tape.
In the case of
VHS, a linear
control track
A control track is a track that runs along an outside edge of a standard analog videotape (including VHS). The control track encodes a series of pulses, each pulse corresponding to the beginning of each frame. This allows the video tape player ...
at the tape's lower edge holds pulses that mark the beginning of every
frame of video; these are used to fine-tune the tape speed during playback and to get the rotating heads exactly on their helical tracks rather than having them end up somewhere between two adjacent tracks. However, the exact distance between the rotating video head and the fixed head reading the linear track can vary by a couple of micrometers between machines due to manufacturing tolerances, so most machines offer a manual or automatic tracking control to correct such mismatches.
References
Video signal
Videotape
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