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OPERATION
The 4025 also contains an LTC/VITC reader which can be operated as two
separate readers (known as Reader 1 and Reader 2), or, they may be
operated as one Auto reader which reads both LTC and VITC. In this
case, the Auto reader is assigned to Reader 1 and Reader 2 is turned off.
The generator time may be preset from the front panel, or slaved to the
incoming bi-phase tach pulses from the telecine.
synced to the Reader 1 time. An optional Offset between the reader and
generator may be applied during jam sync.
The generator user bits may be used as numeric (hexadecimal) data preset
from the front panel, slaved to the incoming bi-phase tach pulses from the
telecine, or slaved to the Reader 2 time. When slaved to the telecine, the
user bits normally contain the film edge number (counting footage with
frames) plus an optional fixed prefix number. In the VITC, the film edge
numbers follow the actual film frame numbers on a field by field basis,
accurately tracking the 2/3 pulldown in NTSC 24 frame per second
transfers. See section 3.10.1 for a full description of the various edge code
numbering modes available in the 4025.
The time numbers are normally the same for both the LTC and the primary
VITC generators. However, because the LTC is only a frame rate code,
the film edge numbers in the user bits are only accurate to the closest
frame in the LTC output. The VITC output is field accurate when the LOCK
LED is On.
The L-GEN, V-GEN, RDR1 or RDR2 keys in the display key group are
used to display either the LTC or primary VITC generator, or either of the
readers on the front panel display. The leftmost characters of the front
panel display are used to prompt which data is being displayed.
TIME / UB key selects whether the generator time or user bits is being
displayed. Each time it is pressed, the display alternates between the time
and user bits. The colons of the display are blanked when user bits are
displayed.
3.9.1
Understanding Time Code 'Add One' Compensation- How it
Affects the Accuracy of the Timecode and Burn-ins
Most time code readers assume that the user bit information is not
changing, and hence make no provision to compensate the user bits for the
delays involved with reading the numbers. Timecode generators that are
built in to the VTR's also suffer from this problem when they are 'slaving' to
external timecode.
transfer this information to the generator, with one or two fields of delay.
The time numbers are compensated for the reading delays, so this problem
affects only the user bits. This phenomena applies to the timecode being
recorded on tape using the 're-gen' mode of the VTR's generator and to the
character generator outputs from the VTR's build in readers.
The following precautions should be taken to ensure that the numbers
being laid down on tape, and window dubs of them are accurate:
Model 4025 Film Footage Encoder Manual
Specifically, they read the incoming user bits and
It may also be jam
The
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