GRASS VALLEY 1200, Installation And Service

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Section 3 Ñ Functional Description
Preset Pattern Keys
Pattern New is the outer edge of the new video and Pattern Old is the
inside edge of the old video. The space between (if any) is the border. The
positions of these signals are determined by the Keyer Module.
The Pattern Old signal passes through the Tri Clip and Gain circuit and
gets selected by the multiplier. The key opacity multiplier uses data from
the CPU to determine how opaque the key signal should be. The key signal
is then delayed, and if the Borderline is not used, the signal is sent to the
Mixer Module. If the Borderline is used, the signal is sent to the Borderline
Submodule where the key is modified. The signal is then sent to the Mixer
Module. Pattern Old is also selected by the Select circuit and sent to the
additive mixer where it is used to shape the video.
The preset pattern border is created by subtracting the Pattern Old and
Pattern New signals. The resulting signal enters the Preset Pattern Border
Mix circuit which creates the border matte. The border then goes to the
Additive Mixer.
The video signal is first sent through a Proc Amp before going to the
Additive Mixer.
The Additive Mixer combines the video and border using the Pattern Old
signal to create the video with the border inserted. The video signal is then
sent to the Mixer Module if the Borderline is not used. If the Borderline is
used, then the video goes through the Borderline Submodule before it is
sent to the Wipe Module.
Luminance, Linear, and Chroma Keys
The Key signal and the Pattern Old signal enter the Clip and Gain circuit.
If there is no mask applied to the key, only the Key signal exits the Clip and
Gain. If there is a mask applied to the key, both the Key and the Pattern Old
exit. The multiplier then multiplies the Key and Pattern Old to produce the
masked key.
The masked Key signal enters a multiplier with opacity data from the CPU
to give the key the desired opacity. If there is no Borderline, the signal is
delayed and sent out to the Mixer Module. If Borderline is selected, the
signal is sent to the Borderline circuit and then out to the Mixer Module.
The signals being sent to the Additive Mixer depend on several factors. See
the previous page for details.
The video first passes through a Proc Amp and is then applied to the
Additive Mixer where the key and video are combined. If the Borderline
Submodule is used, the video passes through the Borderline Submodule
before it is sent to the Mixer Module.
A Chroma Key is handled the same as a Linear Key.