Problem with minimum matching threshold parameter of ByteTracker

[rsnk96]

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• I have searched the Supervision issues and found no similar bug report.

Bug

Hi folks. Amazing project, but I'm getting a peculiar behaviour in ByteTracker.

My assumption for the minimum_matching_threshold parameter of ByteTracker is that it acts similar to an IoU threshold. A smaller threshold should make boxes match more easily, and a larger threshold should make boxes match only if they have a really good match score (ex: really high IoU). However, I observe the inverse behaviour. Not sure if this is expected, but thought I'll highlight it here

Environment

• Supervision: 0.25.0
• Ubuntu: 22.04
• Python: 3.10

Minimal Reproducible Example

Code block to reproduce:

import supervision as sv
import numpy as np

detections = [sv.Detections(xyxy=np.array([[10, 10, 20, 20]]),class_id=np.array([1]),confidence=np.array([1]))]*2
detections+= [sv.Detections(xyxy=np.array([[11, 11, 21, 21]]), class_id=np.array([1]), confidence=np.array([1]))]*2   # 90% overlap

byte_tracker_low_threshold = sv.ByteTrack(minimum_matching_threshold=0.1)
tracked_detections = [byte_tracker_low_threshold.update_with_detections(d) for d in detections]
print("Track IDs associated with detections in 10\% overlap: ", list(t_det.tracker_id for t_det in tracked_detections))
print("Internally tracked states in 10\% overlap: ", byte_tracker_low_threshold.tracked_tracks)

print()
print()

byte_tracker_high_threshold = sv.ByteTrack(minimum_matching_threshold=0.9)
tracked_detections = [byte_tracker_high_threshold.update_with_detections(d) for d in detections]
print("Track IDs associated with detections in 90\% overlap: ", list(t_det.tracker_id for t_det in tracked_detections))
print("Internally tracked states in 90\% overlap: ", byte_tracker_high_threshold.tracked_tracks)

Gives the output:

Track IDs associated with detections in 10\% overlap:  [array([1]), array([1]), array([], dtype=int64), array([2])]
Internally tracked states in 10\% overlap:  [OT_1_(3-4)]


Track IDs associated with detections in 90\% overlap:  [array([1]), array([1]), array([1]), array([1])]
Internally tracked states in 90\% overlap:  [OT_0_(1-4)]

I would expect the opposite to be true, i.e. when we set a low minimum_matching_threshold, it should assign the same track ID to detections more easily (with less IoU overlap). However, that doesn't seem to be the case.

Additional

No response

Are you willing to submit a PR?

• Yes I'd like to help by submitting a PR!

[rolson24]

Hi there @rsnk96!

This is the expected behavior of this threshold, although you are correct that it is poorly named. What it really represents in the code is the MAXIMUM allowed COST of matching a track to a new box, or you can think of it as the MINIMUM allowed SCORE (1 - cost) of matching a track to a new box.