Developer Information
75
Status Updates
When any route, label, or lock is changed on the Videohub Server by any client, the Videohub Server
resends the applicable status block, containing only the items that have changed. For example, if serial
port 6 has been unlocked, the following block will be sent:
SERIAL PORT LOCKS:↵
5 U↵
↵
If multiple items are changed, multiple items may be present in the update:
OUTPUT LABELS:↵
7 New output 8 label↵
10 New output 11 label↵
↵
If a card is plugged into or removed from the Universal Videohub, it will send hardware status blocks for
the video inputs, video outputs, and serial ports on that card.
Requesting Changes
To update a label, lock or route, the client should send a block of the same form the Videohub Server
sends when its status changes. For example, to change the route of output port 8 to input port 3, the
client should send the following block:
VIDEO OUTPUT ROUTING:↵
7 2↵
↵
The block must be terminated by a blank line. On receipt of a blank line, the Videohub Server will either
acknowledge the request by responding:
ACK↵
↵
or indicate that the request was not understood by responding:
NAK↵
↵
After a positive response, the client should expect to see a status update from the Videohub Server
showing the status change. This is likely to be the same as the command that was sent, but if the request
could not be performed, or other changes were made simultaneously by other clients, there may be
more updates in the block, or more blocks. Simultaneous updates could cancel each other out, leading
to a response that is different to that expected.
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