Grass Valley Switcher Products - Manual (Page 110)

110 Switcher Products — Protocols Manual
Section 4 — DPM CPL Protocol
“Front” is the side of the picture plane which would be visible if no rotation
is applied to the transformation; “back” is the opposite side.
“Near” is the side which is visible; “far” 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 picture’s rota-
tion 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 switcher’s 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 selec-
tion will cause a change in both the front and back sides.
The AUX BUS menu displays both the DPM’s 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 flag, 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 Kalypso systems, holds can be imposed to prevent source selections
from changing as effects are recalled or run. Two ways to do this involve
selecting the
Hold button to the right of the source buttons, or holding down
a source button on a bus. Aux buses assigned to a DPM are actually con-
trolled by the DPM, not the Kalypso system. In order to provide the same
level of hold control for these aux buses, the Kalypso system takes control
of an aux bus back from the DPM when that bus has a hold imposed upon
it. When the bus is being held by either mechanism, the Kalypso system
makes the source selection and ignores any source changes for that bus sent
by the DPM. The DPM is still informed of source selections made from the
Kalypso system via the normal mechanisms.
Tally
The switcher subscribes for PID_VIDEO_ON_AIR and PID_KEY_ON_AIR
information from the DPM. The DPM must compute whether a channel’s
image is on screen or not and update these subscriptions when necessary.