evertz 4025TR Instruction Manual page 22

Model 4025TR Film Footage Encoder Manual
The 4025TR Film Footage Encoder uses the telecine's bi-phase
quadrature tach pulse to keep track of the film motion. In addition, a field
sequence pulse from the telecine identifies which field of the 2/3 pulldown
is in the current video field, thus enabling the 4025TR Film Footage
Encoder to identify the precise film frame that is contained in each video
field.
Latent edge numbers have been present on motion picture negative film
stocks for many years in human readable form. The edge numbering
format has been specific to various manufacturers and film stock types,
some having 4, 5, 6 or 7 digits with varying numbers of alpha-numeric roll
numbers, or prefix numbers to the footage. Using normal BCD encoding,
there is only room to encode a maximum of 6 digits of film feet plus 2 digits
of frames into the user bits. By using a compressed binary format, up to 7
digits of feet plus frames can be encoded, however, special decoding
routines in the time code readers are required to recover this information
and display it as decimal digits.
In 1993, Evertz Microsystems led a group of manufacturers in the
development of a standard method of encoding the timecode and film
information into 3 Vertical Interval time code lines. This encoding method,
known as 3 line VITC is an expansion of the Evertz 2 line encoding
developed in 1991 for the 4025 Film Footage Encoder. The 3 line VITC
standard is currently before the SMPTE Time Code standards committee
for standardization. In the 3 line VITc standard, the video timecode and
user bits is recorded on the first line of the 3 line block. The film KeyKode,
transfer rate, and pulldown information is encoded in the second line. The
production timecode information is encoded in the third line of the block.
The second and third lines are protected with special CRC so that their
special encoding format will not confuse standard VITC readers in the
VTR's.
The 4025TR Film Footage Encoder allows the user to select which
encoding style he prefers, permitting compatibility with the largest number
of readers in the industry.
In 1988, Eastman Kodak, in conjunction with the Society of Motion Picture
and Television Engineers devised a new edge print that not only
standardizes the numbering format, but is also printed as a machine
readable barcode. Kodak calls this numbering system KeyKode. Other
film manufacturers have adopted this numbering standard and have each
given their version a proprietary name. For the sake of clarity we shall
refer to all of these implementations as KeyKode.
The 4025TR Film Footage Encoder interfaces to external KeyKode readers
manufactured by Evertz Microsystems, ARRI, Cinema Products or
Research In Motion. Each of these units consist of a bar code reader
pickup head, and a decoder device. The pickup head transforms the
optical dark and light bar code into electronic signals and is designed to
mount on the telecine feed roller just before the film enters the gate. The
decoder receives these electronic signals from the pickup head, and sends
the decoded KeyKode number via a serial link to the 4025TR.
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