Tracking objects between NN detections

AndrzejFijalo

Hello there,

I have a question about how object trackers work.

To provide some context, let me briefly explain how my code works:

My yolov5n operates at a maximum of 21 FPS. To minimize latency issues, the RGB camera operates at 20 FPS. We want to use an Object Tracker to reduce false positive detections by not tracking objects that are younger than a few frames.

So, my questions are:

Does the ZERO_TERM_COLOR_HISTOGRAM tracker type provide some tracking information between detection instances? To elaborate, if I have 3 consecutive frames and an object is detected in the first and third frames, does the tracker give ROI information in the second frame?
When does the Tracker set the object status as LOST? Is it when it doesn't get object coordinates from the detector, or are there some other conditions?
How many frames pass between the LOST and REMOVED statuses?

Thank you, Andrzej

jakaskerl

Hi AndrzejFijalo

AndrzejFijalo Does the ZERO_TERM_COLOR_HISTOGRAM tracker type provide some tracking information between detection instances? To elaborate, if I have 3 consecutive frames and an object is detected in the first and third frames, does the tracker give ROI information in the second frame?

Yes, the type will provide tracking information in case the object cannot be found.

AndrzejFijalo When does the Tracker set the object status as LOST? Is it when it doesn't get object coordinates from the detector, or are there some other conditions?

The status is set to of as soon as the NN node is not passing it any detections.

AndrzejFijalo How many frames pass between the LOST and REMOVED statuses?

In my experience the upper limit is 120 frames. After that, the status will be set to removed. But if the tracker's algorithm predicts the objects (which was tracked before, but is lost now) trajectory would have taken the object out of frame, the status will prematurely be set to removed.

Thanks,
Jaka

AndrzejFijalo

Very big thanks for quick response!

so in example i take to elaborate, on second frame object will have status TRACKED or LOST?

jakaskerl

Should be lost 🙂

Thanks,
Jaka

AndrzejFijalo

Now it's all clear for me 🙂

Thanks a lot