Feedback Mechanism; Feedback Expressions - Cisco TelePresence System Codec C40 Reference Manual

Cisco TelePresence System Codec C40/C60
Contents Introduction

Feedback mechanism

To build solutions that can reliably keep the state between the
application and the codec synchronized, you need to set up
a notification system to report the changes in the state of the
codec.
The API supports notifications on the following:
• Configuration changes
• Status changes
• Event notifications
These notifications will not be sent unless the user has
explicitly told the codec to do so. The user is required to
subscribe to all the feedback the application needs. This
is done by registering feedback expressions. The way of
registering feedback expressions varies according to the
connection method used.
When using HTTP, the method of handling feedback
differs slightly from what is presented in this section. See
"Feedback from codec over HTTP" on page 20
information.
WARNING: A codec may give very much feedback,
especially when calls are connected and disconnected.
Therefore, you should only subscribe to the feedback that
you need.
Never register for all status feedback by issuing
xFeedback register /Status. This may give the control
application too much data to handle, which may lead to
sluggish or unpredictable behavior.
D14642.15 Codec C40-C60 API Reference Guide TC7.0, JANUARY 2014.
About the API About the API

Feedback expressions

The expression used when registering for feedback is a
variant of the XPath language. This language describes a
way to select nodes from an XML document. TC software
contains three main feedback documents:
Document API command
Status xStatus
Configuration xConfiguration
Event xEvent
The syntax for feedback registering is:
<path>
Never register for all status feedback by issuing
xFeedback register /Status.
It is safe to register for all configuration changes using
for more
xFeedback register /Configuration, as configuration changes
will most likely not occur that often.
By going through some examples, we can see how this
information can be used to build feedback expressions. A
good way to verify the expressions is to point your browser
to http://<ip-address>/getxml?location=path
xgetxml <path> from the terminal, and check that the output
matches the nodes you want feedback on.
xConfiguration xCommand
Path
/Status
/Configuration
/Event
xFeedback register
or to execute
17
API Reference Guide
xStatus
Example 1: Microphones Mute status.
Terminal query
xStatus Audio Microphones Mute
*s Audio Microphones Mute: Off
** end
Equivalent feedback expression
xFeedback register /Status/Audio/Microphones/Mute
Example 2: All video input connectors.
Terminal query
xConfiguration Video Input Source Connector
*c xConfiguration Video Input Source 1 Connector:
HDMI
*c xConfiguration Video Input Source 2 Connector:
HDMI
*c xConfiguration Video Input Source 3 Connector:
DVI
** end
Equivalent feedback expression
xFeedback register /Configuration/Video/Input/
Source/Connector
Example 3: Video input connector for source 3.
Terminal query
xConfiguration Video Input Source 3 Connector
*c xConfiguration Video Input Source 3 Connector:
DVI
** end
Equivalent feedback expression
xFeedback register /Configuration/Video/Input/
Source[@item='3']/Connector
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