Brightness change detected as motion

[bossjl]

Hello , it's a great tool, but is there any way to handle brightness changes (like sun and clouds ) without triggering a motion detection?
Maybe by defining the max size that a changing area/blob can have (like 25% of the full image) ?

[Breakthrough]

Hey @bossjl;

Hoping some others more familiar with methods to resolve this can chime in. Ideally the brightness changes could be smoothed out with another method (e.g. histogram matching), but what you suggest also seems feasible as well. It would be the same thing as setting both a minimum and a maximum threshold (versus what happens now, which is just a minimum). I'm unsure as to how robust of a solution that would be, so I definitely would like to do some more research and hear some other ideas on the topic first.

As-is, I think anyone should be able to add in a maximum threshold argument, so I'll tag this as help wanted for now.

Thanks for the suggestion!

[Breakthrough]

@bossjl do you happen to have any sample videos exhibiting this that I could use for testing? Thanks!

[Breakthrough]

Did some quick research into this, it may be worth investigating if OpenCV exposure compensation will work here. It's primarily intended for stitching different images together, so it might be overkill - need to do some performance checks.

Other than that, we can consider some kind of histogram matching as a first pass, and occasionally update the reference histogram when some measure - say the average brightness of the frame - changes by a certain threshold. The downside of this however is it might be a relatively large performance hit, so it would likely need to be an option rather than always enabled.

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Edit: A relatively simple solution might be to average each frame, and use it to calculate a rolling average. Then, multiply all pixels in the frame by the required amount so that it's average is the same as the rolling average. Too simple - this causes even worse results, since it also affects light areas which may not be underexposed. Need to consider some kind of exposure compensation algorithm which may apply different corrections to different parts of the frame.

[gch1p]

@Breakthrough hi, i'm interested in this too and looking for solutions, if you want i can provide you with a sample video for testing (contains both real motion and brightness change caused by sun and clouds)

[Breakthrough]

Hello @gch1p, yes if you could provide a sample that would be very useful. Thank you!

[gch1p]

Hello @gch1p, yes if you could provide a sample that would be very useful. Thank you!

Alright, can you give me your email? Or some other contact where I can send it privately

[Breakthrough]

Is it possible to post it publicly here? If possible I would like to add it to the repo to use as a future development / test cases. If not, that's understandable. Thanks!

[jchennales]

Hi. hoping to revive this. Attaching a false-positive from clouds passing by. You can use it at will.
May I suggest doing the exposure compensation technique but not on every frame but only on the ones that have triggered the "normal" detection method? Like a "second-phase" check.
BrightnessFalsePositive.zip
Great program! Keep at it :)

[jchennales]

btw, this was generated with --threshold 0.85 -a 144 911 445 907 474 1080 141 1080
(a very small region on the bottom left driveway)