Grass Valley Switcher Products - Manual (Page 109)

Switcher Products — Protocols Manual 109
Source Selection
Source Selection
There are multiple parts to the source selection part of the interface.
When the operator makes a selection on the aux row of the control panel (or
via a remote aux panel), the switcher sends a message to the DPM with the
video or key source, never both. The switcher relies on the DPM's use of
source memory to select the appropriate key source. Essentially, the
switcher is simply telling the DPM that an operator pressed a button. It is
up to the DPM to process this information is an expected manner.
The switcher will send a selection for the front source, the back source or
both depending on the near/far selection made from the switcher’s AUX
BUS menu.
The following SET commands communicate this information to the DPM.
These messages include front/back information in the device ID field. The
channel bit is set in the upper 16 bits. The lower 16 bits indicate if the front
or back side is being set (1 = back). These fields are defined as bit maps so
that multiple channels may be set at once. However in practice, a source set
command applies to only one channel at a time.
PID_VIDEO_SOURCE
PID_KEY_SOURCE
Note The switcher does not make aux bus selections as a direct result of an aux
row button press. If the DPM does not respond to the source message, the
switcher’s aux bus source will not change.
As an independent mechanism, the DPM sends messages with the video
and key sources, and the front/back status per channel. They are separate
SET messages, with the content of these parameters:
PID_FRONT_VIDEO_SOURCE_LIST (for 8 channels)
PID_BACK_VIDEO_SOURCE_LIST
PID_FRONT_KEY_SOURCE_LIST
PID_BACK_KEY_SOURCE_LIST
PID_FRONT_BACK_SELECT_LIST
The DPM must send source information on changes. Sending at regular
intervals (e.g., every-field) 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 dif-
ferent, but related ways: