Tracking error

[cl3m3nt]

Hi @charlesollion, @AntoineBruge

I recently used mot code to deploy AI into production.
I noticed an unexpected behaviour at the end of inference process, which seems related to update in tracking method that has happened I guess within june 2020 commit. You'll find below error message code output. You'll see that inference still looks good (100%), however tracking raised an error message.
Hopefully you can have a look, meanwhile I fell back to march commit 9a3fd37 which is definitely ok.

[0115 08:09:59 @inference.py:190] 95 images to analyze on 3 CPUs.
100%|#################################################| 95/95 [01:55<00:00, 1.22s/it]
[0115 08:11:54 @inference.py:201] Finish analyzing video tmp/tmp_gopro.mp4.
[0115 08:11:54 @inference.py:204] Starting tracking.
build tracks length tracklets: 177
[2021-01-15 08:11:55,837] ERROR in app: Exception on / [POST]
Traceback (most recent call last):
File "/usr/local/lib/python3.6/dist-packages/flask/app.py", line 2447, in wsgi_app
response = self.full_dispatch_request()
File "/usr/local/lib/python3.6/dist-packages/flask/app.py", line 1952, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/usr/local/lib/python3.6/dist-packages/flask/app.py", line 1821, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/usr/local/lib/python3.6/dist-packages/flask/_compat.py", line 39, in reraise
raise value
File "/usr/local/lib/python3.6/dist-packages/flask/app.py", line 1950, in full_dispatch_request
rv = self.dispatch_request()
File "/usr/local/lib/python3.6/dist-packages/flask/app.py", line 1936, in dispatch_request
return self.view_functionsrule.endpoint
File "/src/mot/serving/app.py", line 11, in index
return handle_post_request()
File "/src/mot/serving/inference.py", line 60, in handle_post_request
return handle_file(request.files['file'], upload_folder, **request.form)
File "/src/mot/serving/inference.py", line 206, in handle_file
tracks = object_tracker.compute_tracks()
File "/src/mot/tracker/object_tracking.py", line 249, in compute_tracks
matched_tracks = self.match_tracklets(filtered_tracklets, average_speed)
File "/src/mot/tracker/object_tracking.py", line 311, in match_tracklets
sim_matrix = self.build_tracklet_similarity_matrix(tracklets)
File "/src/mot/tracker/object_tracking.py", line 204, in build_tracklet_similarity_matrix
m[i,j] = tracklets[i].compatibility(tracklets[j])
File "/src/mot/tracker/object_tracking.py", line 108, in compatibility
return similarity(old_detection, new_detection)
File "/src/mot/tracker/object_tracking.py", line 16, in similarity
ratiodiff = min(1.0, abs(ratio(new_box) - ratio(old_box)))
File "/src/mot/tracker/tracker_utils.py", line 7, in ratio
return (box[2]-box[0])/(box[3]-box[1])