setting correct motion detection - problem in documentation

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setting correct motion detection - problem in documentation

I am trying to understand the settings for surveillance station, and the documentation provided by Synology only makes it worse...

  1. In this documentation it says:

    Sensitivity: Determine how large the difference is required between a series of frames to trigger motion detection. Larger values will trigger motion detection more easily. The value range is 1 to 99 (%).

    This does not make sense to me. if the sensitivity is representing the difference between frames, than LOWER values will trigger motion more easily, not larger. Maybe the description is incorrect but the way I read it now, if I set the sensitivity to 99% then 99% of the frame has to be different in order to trigger a motion event. So obviously this is wrong, but then what did they really mean by sensitivity.

  2. Then it says:

    Threshold: The threshold of motion detection. Larger values will trigger motion detection for larger movements. The value range is 1 to 99 (%).

    This seems the same definition as sensitivity, but at least this one makes sense.
    I need to understand exactly how those parameters are used to determine an event.

  3. How come it is recording events when the timetable schedule does not have any range selected for any type? I do not have Home mode enabled.

I’m no expert and I kind of gave up on finding the right balance, so I continuously record. Check the following and see if it makes more (or less) sense :)

I came here to post the exact same question @foosy did. The two definitions per synology seem to be controlling the exact same thing in different ways.

The paragraph below from @WST16 amcrest link helped me a little bit, but still trying to wrap my head around it. If I'm understanding correctly:

Sensitivity is a measure of how much of the camera's field of view is being changed, while threshold is a measure of how long the FOV is being changed before it triggers the motion detection? If Threshold is really a movement timer, why not use seconds for the value instead of a 1-99 value that nobody know what it corresponds to exactly?

From the Amcrest link:
"Think about it this way: sensitivity is a measurement of the amount of change in a camera's field of view that qualifies as potential motion detection, and threshold is how much of that motion needs to occur in order to actually trigger the alarm. It can be thought of like this: for however long there is enough change to satisfy the sensitivity parameter, a threshold meter is silently being filled up until it hit's the trigger point."
Although, as I said above, I gave up on finding the right balance and started recording continuously in low resolution and switching to hi res when motion is detected. I’ve switched to my cameras’ ”Smart Events” and that made a big difference with minimizing the false positives. The cameras, rather than SS are responsible for motion detection.

However, let me try to explain the difference (and the relationship) between Sensitivity and Threshold…

While reading the below it’s important to keep in mind that the industry’s motion detection standard is an algorithm that detects changes in the pixels within the field of view (FOV), in other words, what the camera “sees”.

Think of sensitivity as the amount of change (movement) in the camera’s FOV (the pixels changing, even if it’s the same pixels changing, bright to dark for instance).
The size of the object matters. 100 being very sensitive, so small object sizes (few pixel changes) are detected. Big objects far away from the camera are small (fewer pixels), and vice versa, small objects near the camera are big (more pixels).

When the sensitivity is triggered, the threshold parameter (the cup analogy) starts filling until it reaches the set parameter that triggers the alarm. It gets filled when there’s change in the FOV pixels, which is (sometimes mistakenly, like bright to dark pixels) interpreted as movement.

I believe by making it this way it becomes a scale and an easy input to the sensitivity function.

That’s how I understand it and the two functions make sense to me, although I gave up on finding the damn balance between the delivery people, the clouds, the neighborhood cats, the tree foliage with different wind speeds, rain reflections, the birds and everything in between 😐

I hope you see the irony now that it makes sense that it does not make sense 😟

Check this video too…
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