19
the sequence number to controller.
Payload:
According to Payload type, the following data will be saved.
⚫
VISCA command: Save VISCA command packet
⚫
VISCA inquiry: Save VISCA message packet
⚫
VISCA reply: Save VISCA return packet
⚫
VISCA device setting command: Save VISCA equipment setting command packet.
⚫
Control command: The following data is saved in control command payload
⚫
Control reply: The following data is saved in the return command payload of control command.
Delivery confirmation:
VISCA over IP uses UDP as transmission communication protocol. UDP communication message
transmission is not stable, it is necessary to confirm delivery and resent in application.
Generally, when controller sends a command to camera, controller will wait for the return message then
send the next command. We can detect and confirm if the camera receives the commands within its return
message’s lag time. If controller detects overtime, it is regarded as error transmission. Controller will resend
the commands to check camera’s status. The resent command sequence number is the same as the previous
one. Following chart lists possible received message and the corresponding status after the resent command.
Lost message
Received message
for retransmission
Status after
retransmission
Correspondence after retransmission
Command
ACK message
Command is performed by
retransmission.
Continue processing.
Completion message
For the command
ERROR (Abnormality in
the sequence number.)
Command has been
performed.
If only the ACK message is
lost, the completion message
returns.
If the result by the completion message is needed,
retransmit by updating the sequence number.
Completion message
for the command
ERROR (Abnormality in
the sequence number.)
Command has been
performed.
If the result by the completion message is needed,
retransmit by updating the sequence number.
Inquiry
Reply message
Inquiry is performed by
retransmission.
Continue processing.
Reply message for the
inquiry
ERROR (Abnormality in
the sequence number.)
Inquiry has been performed.
If the result by the reply message is needed, retransmit
by updating the sequence number.
Error message
Error message
Command is not performed.
If the error cause eliminates,
normal reply is return(ACK,
reply message)
Eliminate the error cause. If normal reply returns,
continue processing.
Name
Value
Description
RESET
0x01
Resets the sequence number to 0. The value that was
set as the sequence number is ignored.
ERROR
0x0Fyy
yy=01: Abnormality in the sequence number.
yy=02: Abnormality in the message (message type).
Message
Value
Description
ACK
0x01
Reply for RESET.
