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Glossary
R-Y signal
One of the color difference signals, the R
(red) signal minus Y (luminance) signal.
Sampling frequency
The unit of time used when converting an
analog signal with a continuously varying
level to digital form by sampling the level
at a fixed interval. In general, a higher
sampling frequency makes it possible to
digitize analog signals of a higher
frequency.
SCH
Abbreviation of Sub Carrier to Horizontal.
The phase of the subcarrier with respect to
the phase of the horizontal synchronization
signal. In editing of monochrome video,
phase continuity is maintained by editing
in units of frames (two fields), so that the
continuity of the horizontal
synchronization signal phase is
maintained. Editing of color video must be
done in units of two frames (four fields) to
maintain subcarrier continuity. The SCH
of a field can be checked to find out which
of the four fields it represents. This allows
edited video signals to be joined while
maintaining subcarrier continuity.
Search
Viewing the picture or timecode by
running the tape in fast forward or rewind
mode, in order to search for a particular
scene.
Servo
A mechanism that controls the number and
phase of rotations of the head drum or
capstan. Servo mechanism allows
playback of the video signal without guard
band noise. The reference signal of the
servo control is normally a vertical sync
signal.
Servo lock
This refers to the synchronization of the
phase of the drum rotation and the
reference signal for the tape transport
position, so that the video heads can trace
the same pattern on the tape for playback
and recording.
SMPTE
Abbreviation of Society of Motion Picture
and Television Engineers, a professional
association established in the USA.
A-10
Appendixes
S/N
Signal-to-Noise ratio. The relation of the
strength of the desired signal to the
accompanying electronic interference, the
noise. If S/N is high, sounds are
reproduced with less noise and pictures are
reproduced clearly without snow.
Standby-off mode
One of the stop modes. In this mode, head
drum rotation is stopped and the tape
tension is slackened. It is not possible to
switch instantaneously from this mode to
recording or playback mode. This mode is
not harmful to the tape or heads.
Standby-on mode
One of the stop modes. In this mode, the
head drum continues rotating and the tape
remains wound onto the drum. This mode
enables instantaneous switching to
recording or playback mode. To prevent
damage to the tape or heads, the device
automatically switches from standby-on
mode to standby-off mode after a certain
period of time.
Subcarrier
Color information contained in a
composite video signal. Its amplitude is
for color saturation and its phase to color
burst is for hue.
Superimpose
To put one picture (or characters) onto
another so that both can be seen at the
same time.
Sync
A reference signal consisting of vertical
and horizontal sync signals used for
synchronizing the scanning patterns of the
video camera and the monitor.
Tape tension
The tension applied to a tape. For the tape
to run properly while being wound on the
drum, it must be pulled lightly in the
opposite direction to the direction of
transport. Improper adjustment of tape
tension can cause deviations along the
temporal signal axis. In analog VTRs,
these deviations are evident as skew and
distortion in the upper part of the screen.
Time code
The timecode is a tape position
information signal that includes time and
frame data that are recorded onto the tape
so as to facilitate searching of editing
points and recorded scenes when viewing
or editing.
SMPTE timecode is applied to NTSC
system, and EBU timecode is applied to
PAL/SECAM systems. There are two
kinds of signal recorded on tape. One is
longitudinal timecode (LTC) recorded
along the tape (the same way as audio and
CTL signals). The other is vertical
interval timecode (VITC). This code is
inserted in the vertical blanking period and
its recorded on the tape with video signals.
Time data
This refers either to time data that is
generated by a timecode generator or time
data that is played back from a tape and
read by a timecode reader.
Unloading
When the EJECT button is pressed, the
VTR automatically winds the tape back
into the cassette case. Also called
"Unthreading".
User bits
These are also referred to as "users' bits".
The user bits are a 32-bit segment of the
timecode recording area. The user can
select what to record in this segment and
how to use the recorded data. For
example, it can be used to record data
information in addition to the timecode
data or ID numbers for tape reels or
programs.
LTC user bits is used to record good shot
marks.
V (vertical)-blanking
The portion of the video signal that occurs
between the end of one field and the
beginning of the next. During this time,
the electron beams in monitors are turned
off so that they can return from the bottom
of the screen to the top without showing
tracks of movement on the screen. When
the position of v-blanking is not adjusted
correctly, a horizontal black bar appears on
the screen.
Video gain
Amount of amplification for video signals,
expressed in decibels (dB).
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