ok I have found this new DS5.0GA parameter: minTrackingConfidenceDuringInactive. It is set to 1.0 in the sample config file provided with deepstream.
See this blog post where they are talking about zombie/lingering detections. They suggest increasing minTrackingConfidenceDuringInactive to 99.
However if I actually DECREASE this value to 0.5 then the flickering bboxes goes away and they move nice and smooth - like they should for a tracker.
But this is going to mean I get those lingering zombie bboxes right?
So it seems that when minTrackingConfidenceDuringInactive is 1.0 or greater you will only see bboxes drawn when the pgie makes a detection - which is why they flicker. It would probably be better if you set pgie interval to 0 to help reduce the flicker.
So if pgie interval is > 1 then you need to reduce the minTrackingConfidenceDuringInactive value to be less than 1.0. (I have just tested with 0.5) to stop the flickering.
I will play around with these minTrackingConfidenceDuringInactive values some more to find a suitable value. But that leave the open question of how to stop these lingering zombie bboxes…