Grass Valley K2 Edge Protocol Manual v1.0 - Manual (Page 11)

K2 Edge Protocol Manual – document version 1.0 – Page 11
4.3. The exid field
The exid field in the command string is a mandatory field. This field is reserved for defining a unique
external ID, numeric or alphanumeric, for each command. (An easy way to implement this is to use a 32-
bit or 64-bit integer counter and increment the counter value for each new command.) The exid field and
value are guaranteed to be left untouched and are returned in the feedback. Using the exid field value
found in feedback messages from nexos, it is easy to associate the feedback message with the original
command, which is especially useful when nexos is working on several commands simultaneously.
Keep following rules in mind:
• The exid field is mandatory for all sub commands.
• The exid value format is under control of the initiator (numeric, alpha or mixed).
• The exid value must be unique for each new command sent to nexos.
• The exid field and value are guaranteed to be left untouched and returned through feedback
messages.
• The exid field value is the only way to link feedback messages generated by nexos back to the
original command.
4.4. The inst field
When nexos receives a command to preload a template for playback, a temporary instance of this
template is created. The instance lifetime covers the preload- and playback phase, the instance will
automatically be removed when playback is finally stopped. Each template instance needs a unique
identifier so that commands can address it.
For example: sub command preload is used to preload a template instance with instance ID value X;
the following play sub command must specify the same identifier value X, so nexos can locate the
instance. The inst field defines a unique template instance identifier value.
Keep following rules in mind:
1. The inst field is mandatory for the following sub commands: preload-play, preload and play.
2. The inst field value format is numeric.
3. For each preload or preload-play command, a unique inst field value must be defined, since
each time these commands are issued a new template instance is created.
4. Note that when working with the preload and play commands (instead of preload-play), the field
values for the play and preload commands must be identical, since both commands will refer to
the same template instance.