View source for How to use your external camera's motion detection with ZM

[[Various Learnings from getting Zomeminder 1.28.1 working well on Ubuntu Server 14.04|<Home]]

===Background===
Zone minder has an awesome 'trigger' architecture which allows any external event to trigger a recording on ZoneMinder. This section explains the basic architecture and then goes on to describe how you can use your own camera's HW motion detection to trigger a recording on ZM. You can replace this 'trigger' with any other event - such as, for example, triggering your ZM recording when say your Nest thermostat goes to Away mode. The options are limitless

=== Core Trigger Architecture===

 <nowiki>
                      +-----------------+                                                                
                      |  zmtrigger.pl   |  record on/off                                                 
                      |listening on port|  directives over TCP (and other IPC mechanisms)                                          
                      |      6802       |<------+                                                        
                      |                 |       |                          polling or notification   x   
                      +-+---------------+       |                          - depends on device      / \  
                        |                       |                          capabilities            /   \ 
                        |                       |                                 +--------------->     |
                        |                       |                                 |                \   / 
                        |                       |                                 |                 \ /  
+----------------+      | record                |       +---------+               |                      
|                |      |                       |       | my own  |               |                device
|  Rest of Zone  |      |                       +-------| script  |<--------------+                      
|     Minder     <------+                               +---------+                                      
|                |                                                                                       
+----------------+                                                                                       
</nowiki>

If you enable OPT_TRIGGERS in Options->System, then ZoneMinder starts a process called "zmtrigger.pl" (/usr/bin/zmtrigger.pl). This is a perl script that basically offers an easy to use interface for anyone to send it commands to its default TCP port (6802) to initiate/stop recordings. Note that zmtrigger also offers other means of IPC - I just found the TCP channel easy and reliable. 

zmtrigger does not care what caused the event. All it is waiting for is a simple text instruction from anyone capable of sending a command to port 6802. So what that means is I can write any program that monitors anything, and when my program thinks something happened which warrants a recording, all I need to tell zmtrigger is "please record monitor 3" (and optionally specify more parameters)

===Requirements for Triggering===
* OPT_TRIGGERS need to be enabled
* After changing the OPT_TRIGGERS setting you need to either restart zoneminder so that it starts the zmtrigger.pl daemon
* Prior to ZoneMinder v1.30.2, the monitor mode MUST be set to Nodect (ZM won't initiate recordings if in any other mode).
* In 1.37 there is no Nodect setting, instead on the Storage tab, set Recording = OnMotion instead of None.

(To combine both ZM normal recording, and say external triggers, with ZoneMinder prior to v1.30.2 you can always add two monitors pointing to the same camera - one in say modect and the other in nodect and use the latter one for external triggers)

===Quick test===
Lets assume you have a monitor id of 1. As a quick test, just try this 
<nowiki>
telnet zm_ip 6802
 </nowiki>
And when connected via telnet simply type in
 <nowiki>
1|on+20|1|External Motion|External Motion
</nowiki>

You should see ZM create a new recording for Monitor ID=1 for 20 seconds with a name and cause of "External Motion"

===Implementation Strategy===

* Foscam's [http://foscam.us/forum/cgi-sdk-for-hd-camera-t6045.html CGI document] shows that if the camera's motion detection is enabled, then when it detects motion, you can use the getDevState command - if the value of XML tag <motionDetectAlarm> is 2 then motion is detected. It resets back to 1 if there is no motion detect
* Unfortunately, Foscam does not support posting events/callbacks when motion is detected. Note that there are cameras that support web hooks for motion notifications, like Axis cameras.
* so I need to poll it once every few seconds and check this value
* If this value == 2, send a record request to zmtrigger (and thanks to ZM's ring buffer, I won't miss the image that caused the alarm)

===Source code===
Here is the code to do just that (and some other checks for optimization)
It loops through all my cameras and sends triggers when motion is detected

https://github.com/pliablepixels/ZoneMinderFoscamHDTrigger/blob/master/arc_zm_foscamHDmotion.pl
uh-oh, looks like I deleted that repo by mistake. I don't have a copy. But looks like someone else took that code and improved it - see his repo here https://github.com/jshank/ZoneMinderHikvisionTrigger

===Notes===
* Your imagination is the limit here - you can create triggers for any thing you want - ZM doesn't care what the trigger is. As long as your script tells zmtrigger to start/stop recording and for which monitor, that is all ZM needs
* I initially used my camera's HW motion detection for a few weeks, after getting frustrated trying to configure ZM's own zone system, but when I understood how to use ZM's own zone detection, it was better
* If you are worried if this constant pinging of the foscam may slow it down, it does not. I used it for weeks without any problem

===References I found useful===
http://www.sparxeng.com/blog/software/zoneminder-network-triggering