Feedback Mechanism - Cisco Codec C20 Reference Manual

Cisco TelePresence System Codec C20
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 regis-
tering 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 the
"Feedback from codec over HTTP" section for more 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 appli-
cation too much data to handle, which may lead to sluggish
or unpredictable behavior.
Codec C20 API Reference Guide TC6.0 February 2013.
D14869.05
About the API About the API xConfiguration
Feedback expressions
The expression used when registering for feedback is a vari-
ant 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:
N eve r re g i s te r fo r a l l s t at u s fe e d b a c k by i s s u i n g
xFeedback register /Status.
It is safe to register for all configuration changes using
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.
19
xCommand
example 1: Microphones Mute status.
Terminal query
xStatus Audio Microphones Mute
*s Audio Microphones Mute: Off
** end
Path
equivalent feedback expression
/Status
xFeedback register /Status/Audio/Microphones/Mute
/Configuration
example 2: All video input connectors.
/Event
Terminal query
xConfiguration Video Input Source Connector
xFeedback register <path>
*c xConfiguration Video Input Source 1
Connector: HDMI
*c xConfiguration Video Input Source 2
Connector: HDMI
*c xConfiguration Video Input Source 3
Connector: HDMI
*c xConfiguration Video Input Source 4
Connector: HDMI
*c xConfiguration Video Input Source 5
Connector: Composite
or to execute
** 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: HDMI
** end
equivalent feedback expression
xFeedback register /Configuration/Video/Input/
Source[@item='3']/Connector
API Reference Guide
xStatus Appendices
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