Grass Valley 2200 - Manual (Page 98)

5-8
Section 5 Ñ Digital Effects Interface
The DPM must send source information on changes. Sending at regular intervals
(e.g., every-Þeld) is acceptable and can improve recovery should the link be
interrupted.
Near/Far and Front/Back
The switcher differentiates between sides of a planar transform in two different,
but related ways:
ÒFrontÓ is the side of the picture plane which would be visible if no rotation is
applied to the transformation; ÒbackÓ is the opposite side.
ÒNearÓ is the side which is visible; ÒfarÓ is the side which is not visible.
When no rotation is applied, Near = Front and Far = Back.
Use of near and far allow the operator to change sources and insure the change is
either seen (near) or not seen (far) regardless of the pictureÕs rotation amount.
In order for the switcher to sort out near and far, it must be provided with front/
back information from the DPM. Front/Back information tells the switcher which
side is visible, that is, which is the near side.
Selections in the switcherÕs AUX BUS menu allow delegation of the aux selector
row to either near or far or both. The row will change and display the selected
side. If BOTH is selected, the near side is displayed and a selection will cause a
change in both the front and back sides.
The AUX BUS menu displays both the DPMÕs front and back sources, the current
aux selector row delegation (near/far) and which side the DPM has reported as
the near side (front/back).
If the DPM does not fully implement the front and back source selection and
front/back ßag, the switcher will not be able to properly resolve near/far. While
the system will still function, the information displayed to the user may be
incorrect.
Source Hold
On the switcher, holding down a source selection button overrides normal source
selections as effects are recalled or run. Aux busses assigned to the DPM are
actually controlled by the DPM, not the switcher and any hold down override
must be handled by the DPM.
The switcher provides the DPM with the source button hold down indication via
SET, PID_HOLD_INPUT_CROSS_PT.
The switcher also provides a user selection to prevent all source changes when an
effect is recalled or run. This HOLD INPUT button affects all busses of the
switcher, and in the case of Krystal also all channels of digital effects.
PID_HOLD_INPUT_OVERRIDE is used to communicate the global hold input
state.