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multiple zones seem to cause cluttered alarm events

Posted: Tue May 15, 2007 10:30 am
by toskala
hey there,

maybe i need to explain the situation here a little bit. i am monitoring my appartment door from the inside with a direct front view. unfortunately i have a window on the right side which lets sunlight shine more or less directly on the white door. as this caused many false alarms i read through the docs and tried to play with zones and different detection sensibility.
i basically created two zones, one where most of the light/shadow take place with a low sensibility and one that monitors the doorknob area with a higher sensibility.

at first it seemed to work that way but after testing the setup it looks like when i come through the door the doorknob zone causes an alarm and records and if i close the door and move over to the zone "rest of door" it seems to cause another event and generates another alarm.

result now is, that i have two or three small mpeg movies that get emailed to me but i really would love to have one connected movie.

is there a way to, hmm, tell ZM "if an alarm is generated record everything and ignore the other zones until its quiet again"?

maybe i am doing something horribly wrong but even after playing a lot with ZM i seem not able to get this two problems sorted out.


Posted: Tue May 15, 2007 12:18 pm
by jamescollings
When a zone triggers an alarm recording starts. Since zoneminder has a number of frames in its memory (PRE EVENT BUFFER) these are tagged to the begining. when a frame is encountered that isn't an alarm, then a set number of additional frames are recorded (POST EVENT BUFFER). if during the recording of these additional frames another event frame is found (that is, an alarm occurs in a zone), then the alarmed zones are recorded until another "clear" frame is encountered. At this point, it starts recording the "Post Event Buffer" frames again.. and so on and so on, until the Post Event Buffer frames have been recorded without any more alarms occuring.

From what you say, I suspect that your Post Event Buffer is too small, such that they are all recorded (and clear). Then you move your body into the "other" zone and trigger a whole new alarm.

The Pre and Post buffers are counted in Frames, so if you have a buffer of 10 and are recording at 20 frames per second, this means that you will record 0.5 seconds of "clear" frames at the end of an alarm. I have a buffer of 20 and record at only 4 fps. This means that I will get at least seconds of "pre" and "post" alarm activity. It enables me to keep the "centre" of my zones at high sensitivity, and leave the edges as less sensitive (ie: the perp can walk through the least sensitive area, but when they trigger the highly sensitive area, I have their movements in the less sensitive areas recorded in the buffer).

Sorry if this is complicated, it shouldn't be.. .it's just my poor explanation.

Posted: Tue May 15, 2007 12:53 pm
by toskala
ah that perfectly makes sense, from how i walk into the room i first traverse the sensible zone in the middle first and then move over to the not so sensible one. if an alarm occurs i record in 10fps which could cause the problem. i will try to increase the post event buffer and keep you posted after i try that when i am back home :-)

thanks for your reply!

Posted: Tue May 15, 2007 8:04 pm
by toskala
okay, back at home, just caused an alarm myself while coming through my door. i switched the post event buffer up to 20 and now i only have 2 videos left. i guess i will need to fiddle around with that setting a bit more :-)

thanks for your help!