Smoothing detections using tracking

[abhiagwl4262]

Smoothing detections using tracking

[abhiagwl4262]

@kkyiss max_age ensures the case of occlusion. So if a track is lost then we don't keep that track aside, instead we try to track that object until max_age frames(even after disappearance).

I hope, I am clear.

[sherlockchou86]

@abhiagwl4262 has explained why the max_age variable exists in SORT code, but do not answer why he added self.max_age to this line.

by default, the SORT tracker would only return the targets which have been updated(matched by detections or new detections) in current frame. but sometimes some targets would not be detected for few frames by detector, the missed targets would not be returned by SORT in this manner.

if we want SORT to return the missed targets even if they are missed by few frames, we need change the code
if((trk.time_since_update < 1) and (trk.hit_streak >= self.min_hits or self.frame_count <= self.min_hits)):
to
if((trk.time_since_update <= self.max_age) and (trk.hit_streak >= self.min_hits or self.frame_count <= self.min_hits)):
and set min_hits == 0

this means the SORT would return any targets in SORT's cache(predicting location for those not updated), as long as they have not been missed for frames of self.max_age. it is very useful for some situations such as the detector is not good enough and it always misses some small targets in the detecting step before tracking.

there is a drawback that the SORT will return targets which have already disappeared indeed, for example the targets arrive at the edge of the picture and cannot be detected by detector. we should ignore the targets of which location points are out of range, and also the self.max_age should not be set too large or the number of missed targets are too large to maintain in SORT's cache.

[abewley]

You should be able to achieve this through the min_hits and max_age parameters of the tracker initialiser.

[abhiagwl4262]

Thanks. I was able to resolve this issue.
I changed the following line to https://github.com/abewley/sort/blob/master/sort.py#L222
if((trk.time_since_update < self.max_age+1) and (trk.hit_streak >= self.min_hits or self.frame_count <= self.min_hits)):

and set min_hits=0 and max_age=4

[kkyiss]

Hey @abhiagwl4262
Could you tell me why you are adding self.max_age to this line?
thanks!

[BornInWater]

@abhiagwl4262 , if its not too much trouble could you upload a video with the following changes, because i am not able to observe any change when these parameters are changed. The algorithm still dumps the trackers as soon as there is a miss of detection of that object in a frame.