Grass Valley Switcher Products - Manual (Page 14)

14 Switcher Products — Protocols Manual
Section 1 — Tally Protocol
For this reason, each device which processes video must build a “contribu-
tion map” which indicates which of its inputs are visible on or contributes
to each output. Because the video path through the switcher is known, the
tally system can then trace each output back through all paths and find all
contributing sources. The set of contributing sources for each output is
likely to be different, but can be tallied independently.
With this mechanism, most tally modes are a degenerate case of Output
Tally. On-air tally is Output Tally for the PGM PST Program output. Look-
ahead tally is Output Tally for the PGM PST Preview output.
If more than one program output exists, for example, the four program-
mable clean feed outputs of the PGM PST bank, contributions can be com-
bined after tracing each path from output back to all inputs.
Names
All tally information is number based to keep messages short and minimize
communication time. Source names are provided through a separate mech-
anism because they change less frequently and require a higher bandwidth
to transfer.
Source names name the source IDs including reentries.
Tally Relay Outputs
The Kalypso system provides 64 tally outputs as part of the standard
system. A second card can be added for a total of 128 tally relays within the
frame. The Zodiak system has 32 tally relays with no additional cards avail-
able.
On a Kalypso or Zodiak system, tally relays can be configured for different
tally calculations in groups of 32. For example, on a Kalypso system one
group can provide on-air tally while another group can provide bus iso
tally. Each tally relay within the group can be associated with one of the 128
sources. In the previous example, on-air tally can be set up for any 32 of the
128 Kalypso sources using the first group. The second group could provide
bus iso tally for the same set of 32 sources or a completely different set. In
many situations, 32 on-air closures will be sufficient. When this is not the
case, additional groups can also be configured for on-air tally calculations
and mapped to different sources. By using all four tally groups for on-air
tally, all 128 Kalypso sources can be tallied.
Note At the time of publication, switcher tally relays were hard-coded to corre-
spond one-to-one to system sources. The tally relay for any source visible on
any of the outputs of the PGM PST bank will close. Programmable tally
relays, as referenced here, are under development. Check the documentation
of your current switcher software version to determine what tally relay pro-
gramming capabilities are available.