Grass Valley Switcher Products - Manual (Page 30)

30 Switcher Products — Protocols Manual
Section 1 — Tally Protocol
Kayenne Contribution Tally Protocol
This section describes the Contribution Tally Protocol that applies to
Kayenne switchers. This protocol has a modified form of the earlier
Kalypso and Zodiak switcher protocols.
Contribution tally makes it possible to determine which sources contribute
to the image at any point in the video path. On-air tally, for example, iden-
tifies which sources contribute in some way to the main program output of
the switcher.
Contribution messages indicate which sources are selected on buses
feeding each processing block (ME, eDPM, etc.) and which of those inputs
contribute to each output of a processing block. In the case where a pro-
cessing block has several outputs, a separate contribution map is included
for each output.
Contribution information for each processing block is sent as a separate
message. All portions of the system are included in the contribution dump
even if they are inactive. Active blocks will be updated whenever their tally
information changes.
Message Structure and Summary
Messages start with two message code bytes followed by the message data.
• The first message code byte has 0xF in the upper nibble and a command
code in the lower nibble.
• The second message code byte has 0xF in the upper nibble and an
instance number in the lower nibble.
The previous Kalypso protocol used identical two message codes in
sequence to indicate start of message. This algorithm depended on the fact
that message codes were always greater than 128 and source ID’s were 128
or less so that two message codes in sequence was unique. This new
method allows for source ID’s up to and including 240 (0xF0).
Message code bytes always have their most significant 4 bits set on. The
command code is in the least significant 4 bits of the first message code
byte. The instance ID is in the least significant 4 bits of the second message
code byte. The instance ID is 1 based and is never 0.
The new sync algorithm is to detect two consecutive bytes with 0xF in the
upper nibble. This allows message data to use all eight bits. To make the
sync pattern unique, messages have been organized so that bytes con-
taining contribution map data are always separated with bytes containing
source ID data. This makes detecting the beginning of messages possible
and preserves efficient use of message data bytes for encoding tally infor-
mation.