removing distorted frames

Sir Veillance · Post by **Sir Veillance** » Wed Nov 14, 2007 2:50 am

my wireless camera sometimes sends distorted pictures, mostly at night and while it's raining.

Examples:

I have two ideas how to avoid those false alarms:

1: a plugin interface so that people could write filter programs. Those filters would have to be called by ZM before an alarm is generated.

2: (probably easier to implement)
If I store distorted images as reference pictures, ZM could match those against the current event frames, and if there are more than x frames y% similar to the reference frame, then the alarm should be cancelled.

I guess, the comparison routines are already implemented, so this might be fairly easy to integrate into ZM

Definitely, this would help avoid many false alarms (and thus make cheap cameras usable

)

Post by **cordel** » Wed Nov 14, 2007 6:25 am

Or you could set the zones to throw out anything that has more than say 60% change. Analysis is a process hungry application, specially dealing with video where it is process hungry as it is. This would mean that a more robust server would be needed to handle the extra workload which is a greater expence of putting together a server. If your looking to get more reliable alarm status, invest in a PIR and intigrate it into the ZM server. To many things can affect a cameras field of view to cause an alarm where a PIR would limit that to more interesting things. Other wise it would be cheaper to get a good camera.

Post by **zoneminder** » Wed Nov 14, 2007 10:23 am

I am considering the idea of plugins for future development but for now, as cordel mentioned, the best thing would be to put an upper limit on the amount of change that comprises an alarm. If exceeded you can also ignore the next 'x' frames in case it takes a few to settle down.

Ultimately though it's very difficult to come up with a strategy that reliable detects motion etc that you want and also can handle cameras that occasionally just sent rubbish. It's not always easy to tell the difference.

Sir Veillance · Post by **Sir Veillance** » Wed Nov 14, 2007 12:29 pm

I think, the processing time wouldn't be that much of an issue here, because it doesn't have to be done in realtime, but only (as a filter) after an event had occurred.

As for setting maximum alarmed area: this has to be changed in each zone, right?

As for plugins: maybe I can build my own plugin filter using the script interface and one of these programs: Image Magick or jpegdiff

I'll play around with these and let you know what I find out.