/
sort_tracker.py
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/
sort_tracker.py
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import numpy as np
from scipy.optimize import linear_sum_assignment
from motrackers.utils.misc import iou_xywh as iou
from motrackers.track import KFTrackSORT, KFTrack4DSORT
from motrackers.centroid_kf_tracker import CentroidKF_Tracker
def assign_tracks2detection_iou(bbox_tracks, bbox_detections, iou_threshold=0.3):
"""
Assigns detected bounding boxes to tracked bounding boxes using IoU as a distance metric.
Args:
bbox_tracks (numpy.ndarray): Bounding boxes of shape `(N, 4)` where `N` is number of objects already being tracked.
bbox_detections (numpy.ndarray): Bounding boxes of shape `(M, 4)` where `M` is number of objects that are newly detected.
iou_threshold (float): IOU threashold.
Returns:
tuple: Tuple contains the following elements in the given order:
- matches (numpy.ndarray): Array of shape `(n, 2)` where `n` is number of pairs formed after matching tracks to detections. This is an array of tuples with each element as matched pair of indices`(track_index, detection_index)`.
- unmatched_detections (numpy.ndarray): Array of shape `(m,)` where `m` is number of unmatched detections.
- unmatched_tracks (numpy.ndarray): Array of shape `(k,)` where `k` is the number of unmatched tracks.
"""
if (bbox_tracks.size == 0) or (bbox_detections.size == 0):
return np.empty((0, 2), dtype=int), np.arange(len(bbox_detections), dtype=int), np.empty((0,), dtype=int)
if len(bbox_tracks.shape) == 1:
bbox_tracks = bbox_tracks[None, :]
if len(bbox_detections.shape) == 1:
bbox_detections = bbox_detections[None, :]
iou_matrix = np.zeros((bbox_tracks.shape[0], bbox_detections.shape[0]), dtype=np.float32)
for t in range(bbox_tracks.shape[0]):
for d in range(bbox_detections.shape[0]):
iou_matrix[t, d] = iou(bbox_tracks[t, :], bbox_detections[d, :])
assigned_tracks, assigned_detections = linear_sum_assignment(-iou_matrix)
unmatched_detections, unmatched_tracks = [], []
for d in range(bbox_detections.shape[0]):
if d not in assigned_detections:
unmatched_detections.append(d)
for t in range(bbox_tracks.shape[0]):
if t not in assigned_tracks:
unmatched_tracks.append(t)
# filter out matched with low IOU
matches = []
for t, d in zip(assigned_tracks, assigned_detections):
if iou_matrix[t, d] < iou_threshold:
unmatched_detections.append(d)
unmatched_tracks.append(t)
else:
matches.append((t, d))
if len(matches):
matches = np.array(matches)
else:
matches = np.empty((0, 2), dtype=int)
return matches, np.array(unmatched_detections), np.array(unmatched_tracks)
class SORT(CentroidKF_Tracker):
"""
SORT - Multi object tracker.
Args:
max_lost (int): Max. number of times a object is lost while tracking.
tracker_output_format (str): Output format of the tracker.
iou_threshold (float): Intersection over union minimum value.
process_noise_scale (float or numpy.ndarray): Process noise covariance matrix of shape (3, 3)
or covariance magnitude as scalar value.
measurement_noise_scale (float or numpy.ndarray): Measurement noise covariance matrix of shape (1,)
or covariance magnitude as scalar value.
time_step (int or float): Time step for Kalman Filter.
"""
def __init__(
self, max_lost=0,
tracker_output_format='mot_challenge',
iou_threshold=0.3,
process_noise_scale=1.0,
measurement_noise_scale=1.0,
time_step=1
):
self.iou_threshold = iou_threshold
super().__init__(
max_lost=max_lost, tracker_output_format=tracker_output_format,
process_noise_scale=process_noise_scale,
measurement_noise_scale=measurement_noise_scale, time_step=time_step
)
def _add_track(self, frame_id, bbox, detection_confidence, class_id, **kwargs):
# self.tracks[self.next_track_id] = KFTrackSORT(
# self.next_track_id, frame_id, bbox, detection_confidence, class_id=class_id,
# data_output_format=self.tracker_output_format, process_noise_scale=self.process_noise_scale,
# measurement_noise_scale=self.measurement_noise_scale, **kwargs
# )
self.tracks[self.next_track_id] = KFTrack4DSORT(
self.next_track_id, frame_id, bbox, detection_confidence, class_id=class_id,
data_output_format=self.tracker_output_format, process_noise_scale=self.process_noise_scale,
measurement_noise_scale=self.measurement_noise_scale, kf_time_step=1, **kwargs)
self.next_track_id += 1
def update(self, bboxes, detection_scores, class_ids):
self.frame_count += 1
bbox_detections = np.array(bboxes, dtype='int')
# track_ids_all = list(self.tracks.keys())
# bbox_tracks = []
# track_ids = []
# for track_id in track_ids_all:
# bb = self.tracks[track_id].predict()
# if np.any(np.isnan(bb)):
# self._remove_track(track_id)
# else:
# track_ids.append(track_id)
# bbox_tracks.append(bb)
track_ids = list(self.tracks.keys())
bbox_tracks = []
for track_id in track_ids:
bb = self.tracks[track_id].predict()
bbox_tracks.append(bb)
bbox_tracks = np.array(bbox_tracks)
if len(bboxes) == 0:
for i in range(len(bbox_tracks)):
track_id = track_ids[i]
bbox = bbox_tracks[i, :]
confidence = self.tracks[track_id].detection_confidence
cid = self.tracks[track_id].class_id
self._update_track(track_id, self.frame_count, bbox, detection_confidence=confidence, class_id=cid, lost=1)
if self.tracks[track_id].lost > self.max_lost:
self._remove_track(track_id)
else:
matches, unmatched_detections, unmatched_tracks = assign_tracks2detection_iou(
bbox_tracks, bbox_detections, iou_threshold=self.iou_threshold)
for i in range(matches.shape[0]):
t, d = matches[i, :]
track_id = track_ids[t]
bbox = bboxes[d, :]
cid = class_ids[d]
confidence = detection_scores[d]
self._update_track(track_id, self.frame_count, bbox, confidence, cid, lost=0)
for d in unmatched_detections:
bbox = bboxes[d, :]
cid = class_ids[d]
confidence = detection_scores[d]
self._add_track(self.frame_count, bbox, confidence, cid)
for t in unmatched_tracks:
track_id = track_ids[t]
bbox = bbox_tracks[t, :]
confidence = self.tracks[track_id].detection_confidence
cid = self.tracks[track_id].class_id
self._update_track(track_id, self.frame_count, bbox, detection_confidence=confidence, class_id=cid, lost=1)
if self.tracks[track_id].lost > self.max_lost:
self._remove_track(track_id)
outputs = self._get_tracks(self.tracks)
return outputs