Grass Valley SSP-3801 Installation v.1.3 - Manual (Page 44)

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Configuring the SSP-3801 card
Configuring an external router for switching between live events
Configuring an external router for switching between live events
To be able to switch between multiple live feeds, you must connect and configure an
external video router. The router is connected to both the card’s SDI A and SDI B inputs.
Once router control is configured, the card manages which router source on which input is
sent to PGM (SDI Out) output.
A router system is usually comprised of two components: the router controller and the
router frame. The router frame connects the video sources to destinations, which is called
making a crosspoint. The router controller controls when the router frame makes the
crosspoint and to which destination the video source is sent.
The card communicates with the router controller through a network control connection to
signal when to switch crosspoints. The switching between the sources can be made by
source events in the playlist.
The expected flow of events between the card and the router is:
• The card sends a crosspoint (XPT) request to the router controller.
• The router controller receives the request from the card, triggers the router frame to
make the crosspoint, and then checks that the router frame has made the crosspoint.
• The router controller sends a message to the card confirming that the crosspoint has
been made.
In reality many router controllers send the crosspoint complete confirmation message
before it checks if the crosspoint has been made or even before the router frame has
actually made the crosspoint. To prevent unwanted effects in the playout, you can
configure the Post Router Tally Delay to accommodate for the time between the
confirmation message and the actual crosspoint being made by the router frame. It is
important to determine the correct value to configure as the Post Router Tally Delay which
is specific to your system.
As the card manages the selection of the SDI inputs, it biases the routing so the primary live
feed is on the SDI A input. This enables the live feed from the router source to be
automatically passed from the SDI A input to the PGM (SDI Out) output via the mechanical
bypass relay in case of power loss or card failure, therefore ensuring that playout continues
uninterrupted. It also prevents an operator from having to figure out which input is in use if
the wrong source or a bad source is on the PGM output. By biasing the routing to the SDI A
input, the operator can be sure that changing the source on the SDI A input will correct the
feed on the PGM output.
To understand how the switch between inputs occurs, consider this example. Source event
LIVE1 is on air and routed to input A. A second source event, LIVE2, enters the pre-roll
window. LIVE2 is routed to input B and goes on air when LIVE1 is done. The card then sends
a request to the router controller to also route LIVE2 to input A so both inputs are receiving
the same feed. Once the card receives the confirmation message from the router controller
and the Post Router Tally Delay has expired, the card switches its PGM output from SDI B to
SDI A and the transition on air should be seamless. If the Post Router Tally Delay value is too
short, a flash of LIVE1 may be seen on air when the switch is performed as the router will
not have completed its route. For a seamless transition, the Post Router Tally Delay value
must be correct.