445 lines
18 KiB
Python
445 lines
18 KiB
Python
# Ultralytics YOLO 🚀, AGPL-3.0 license
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import numpy as np
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from ..utils import LOGGER
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from ..utils.ops import xywh2ltwh
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from .basetrack import BaseTrack, TrackState
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from .utils import matching
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from .utils.kalman_filter import KalmanFilterXYAH
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class STrack(BaseTrack):
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"""
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Single object tracking representation that uses Kalman filtering for state estimation.
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This class is responsible for storing all the information regarding individual tracklets and performs state updates
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and predictions based on Kalman filter.
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Attributes:
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shared_kalman (KalmanFilterXYAH): Shared Kalman filter that is used across all STrack instances for prediction.
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_tlwh (np.ndarray): Private attribute to store top-left corner coordinates and width and height of bounding box.
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kalman_filter (KalmanFilterXYAH): Instance of Kalman filter used for this particular object track.
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mean (np.ndarray): Mean state estimate vector.
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covariance (np.ndarray): Covariance of state estimate.
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is_activated (bool): Boolean flag indicating if the track has been activated.
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score (float): Confidence score of the track.
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tracklet_len (int): Length of the tracklet.
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cls (any): Class label for the object.
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idx (int): Index or identifier for the object.
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frame_id (int): Current frame ID.
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start_frame (int): Frame where the object was first detected.
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Methods:
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predict(): Predict the next state of the object using Kalman filter.
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multi_predict(stracks): Predict the next states for multiple tracks.
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multi_gmc(stracks, H): Update multiple track states using a homography matrix.
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activate(kalman_filter, frame_id): Activate a new tracklet.
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re_activate(new_track, frame_id, new_id): Reactivate a previously lost tracklet.
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update(new_track, frame_id): Update the state of a matched track.
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convert_coords(tlwh): Convert bounding box to x-y-aspect-height format.
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tlwh_to_xyah(tlwh): Convert tlwh bounding box to xyah format.
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"""
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shared_kalman = KalmanFilterXYAH()
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def __init__(self, xywh, score, cls):
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"""Initialize new STrack instance."""
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super().__init__()
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# xywh+idx or xywha+idx
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assert len(xywh) in {5, 6}, f"expected 5 or 6 values but got {len(xywh)}"
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self._tlwh = np.asarray(xywh2ltwh(xywh[:4]), dtype=np.float32)
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self.kalman_filter = None
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self.mean, self.covariance = None, None
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self.is_activated = False
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self.score = score
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self.tracklet_len = 0
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self.cls = cls
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self.idx = xywh[-1]
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self.angle = xywh[4] if len(xywh) == 6 else None
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def predict(self):
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"""Predicts mean and covariance using Kalman filter."""
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mean_state = self.mean.copy()
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if self.state != TrackState.Tracked:
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mean_state[7] = 0
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self.mean, self.covariance = self.kalman_filter.predict(mean_state, self.covariance)
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@staticmethod
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def multi_predict(stracks):
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"""Perform multi-object predictive tracking using Kalman filter for given stracks."""
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if len(stracks) <= 0:
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return
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multi_mean = np.asarray([st.mean.copy() for st in stracks])
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multi_covariance = np.asarray([st.covariance for st in stracks])
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for i, st in enumerate(stracks):
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if st.state != TrackState.Tracked:
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multi_mean[i][7] = 0
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multi_mean, multi_covariance = STrack.shared_kalman.multi_predict(multi_mean, multi_covariance)
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for i, (mean, cov) in enumerate(zip(multi_mean, multi_covariance)):
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stracks[i].mean = mean
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stracks[i].covariance = cov
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@staticmethod
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def multi_gmc(stracks, H=np.eye(2, 3)):
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"""Update state tracks positions and covariances using a homography matrix."""
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if len(stracks) > 0:
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multi_mean = np.asarray([st.mean.copy() for st in stracks])
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multi_covariance = np.asarray([st.covariance for st in stracks])
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R = H[:2, :2]
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R8x8 = np.kron(np.eye(4, dtype=float), R)
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t = H[:2, 2]
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for i, (mean, cov) in enumerate(zip(multi_mean, multi_covariance)):
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mean = R8x8.dot(mean)
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mean[:2] += t
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cov = R8x8.dot(cov).dot(R8x8.transpose())
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stracks[i].mean = mean
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stracks[i].covariance = cov
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def activate(self, kalman_filter, frame_id):
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"""Start a new tracklet."""
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self.kalman_filter = kalman_filter
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self.track_id = self.next_id()
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self.mean, self.covariance = self.kalman_filter.initiate(self.convert_coords(self._tlwh))
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self.tracklet_len = 0
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self.state = TrackState.Tracked
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if frame_id == 1:
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self.is_activated = True
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self.frame_id = frame_id
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self.start_frame = frame_id
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def re_activate(self, new_track, frame_id, new_id=False):
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"""Reactivates a previously lost track with a new detection."""
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self.mean, self.covariance = self.kalman_filter.update(
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self.mean, self.covariance, self.convert_coords(new_track.tlwh)
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)
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self.tracklet_len = 0
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self.state = TrackState.Tracked
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self.is_activated = True
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self.frame_id = frame_id
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if new_id:
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self.track_id = self.next_id()
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self.score = new_track.score
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self.cls = new_track.cls
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self.angle = new_track.angle
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self.idx = new_track.idx
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def update(self, new_track, frame_id):
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"""
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Update the state of a matched track.
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Args:
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new_track (STrack): The new track containing updated information.
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frame_id (int): The ID of the current frame.
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"""
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self.frame_id = frame_id
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self.tracklet_len += 1
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new_tlwh = new_track.tlwh
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self.mean, self.covariance = self.kalman_filter.update(
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self.mean, self.covariance, self.convert_coords(new_tlwh)
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)
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self.state = TrackState.Tracked
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self.is_activated = True
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self.score = new_track.score
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self.cls = new_track.cls
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self.angle = new_track.angle
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self.idx = new_track.idx
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def convert_coords(self, tlwh):
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"""Convert a bounding box's top-left-width-height format to its x-y-aspect-height equivalent."""
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return self.tlwh_to_xyah(tlwh)
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@property
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def tlwh(self):
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"""Get current position in bounding box format (top left x, top left y, width, height)."""
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if self.mean is None:
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return self._tlwh.copy()
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ret = self.mean[:4].copy()
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ret[2] *= ret[3]
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ret[:2] -= ret[2:] / 2
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return ret
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@property
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def xyxy(self):
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"""Convert bounding box to format (min x, min y, max x, max y), i.e., (top left, bottom right)."""
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ret = self.tlwh.copy()
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ret[2:] += ret[:2]
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return ret
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@staticmethod
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def tlwh_to_xyah(tlwh):
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"""Convert bounding box to format (center x, center y, aspect ratio, height), where the aspect ratio is width /
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height.
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"""
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ret = np.asarray(tlwh).copy()
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ret[:2] += ret[2:] / 2
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ret[2] /= ret[3]
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return ret
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@property
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def xywh(self):
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"""Get current position in bounding box format (center x, center y, width, height)."""
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ret = np.asarray(self.tlwh).copy()
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ret[:2] += ret[2:] / 2
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return ret
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@property
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def xywha(self):
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"""Get current position in bounding box format (center x, center y, width, height, angle)."""
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if self.angle is None:
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LOGGER.warning("WARNING ⚠️ `angle` attr not found, returning `xywh` instead.")
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return self.xywh
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return np.concatenate([self.xywh, self.angle[None]])
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@property
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def result(self):
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"""Get current tracking results."""
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coords = self.xyxy if self.angle is None else self.xywha
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return coords.tolist() + [self.track_id, self.score, self.cls, self.idx]
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def __repr__(self):
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"""Return a string representation of the BYTETracker object with start and end frames and track ID."""
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return f"OT_{self.track_id}_({self.start_frame}-{self.end_frame})"
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class BYTETracker:
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"""
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BYTETracker: A tracking algorithm built on top of YOLOv8 for object detection and tracking.
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The class is responsible for initializing, updating, and managing the tracks for detected objects in a video
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sequence. It maintains the state of tracked, lost, and removed tracks over frames, utilizes Kalman filtering for
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predicting the new object locations, and performs data association.
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Attributes:
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tracked_stracks (list[STrack]): List of successfully activated tracks.
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lost_stracks (list[STrack]): List of lost tracks.
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removed_stracks (list[STrack]): List of removed tracks.
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frame_id (int): The current frame ID.
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args (namespace): Command-line arguments.
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max_time_lost (int): The maximum frames for a track to be considered as 'lost'.
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kalman_filter (object): Kalman Filter object.
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Methods:
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update(results, img=None): Updates object tracker with new detections.
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get_kalmanfilter(): Returns a Kalman filter object for tracking bounding boxes.
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init_track(dets, scores, cls, img=None): Initialize object tracking with detections.
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get_dists(tracks, detections): Calculates the distance between tracks and detections.
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multi_predict(tracks): Predicts the location of tracks.
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reset_id(): Resets the ID counter of STrack.
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joint_stracks(tlista, tlistb): Combines two lists of stracks.
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sub_stracks(tlista, tlistb): Filters out the stracks present in the second list from the first list.
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remove_duplicate_stracks(stracksa, stracksb): Removes duplicate stracks based on IoU.
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"""
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def __init__(self, args, frame_rate=30):
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"""Initialize a YOLOv8 object to track objects with given arguments and frame rate."""
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self.tracked_stracks = [] # type: list[STrack]
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self.lost_stracks = [] # type: list[STrack]
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self.removed_stracks = [] # type: list[STrack]
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self.frame_id = 0
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self.args = args
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self.max_time_lost = int(frame_rate / 30.0 * args.track_buffer)
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self.kalman_filter = self.get_kalmanfilter()
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self.reset_id()
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def update(self, results, img=None):
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"""Updates object tracker with new detections and returns tracked object bounding boxes."""
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self.frame_id += 1
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activated_stracks = []
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refind_stracks = []
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lost_stracks = []
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removed_stracks = []
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scores = results.conf
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bboxes = results.xywhr if hasattr(results, "xywhr") else results.xywh
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# Add index
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bboxes = np.concatenate([bboxes, np.arange(len(bboxes)).reshape(-1, 1)], axis=-1)
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cls = results.cls
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remain_inds = scores >= self.args.track_high_thresh
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inds_low = scores > self.args.track_low_thresh
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inds_high = scores < self.args.track_high_thresh
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inds_second = inds_low & inds_high
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dets_second = bboxes[inds_second]
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dets = bboxes[remain_inds]
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scores_keep = scores[remain_inds]
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scores_second = scores[inds_second]
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cls_keep = cls[remain_inds]
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cls_second = cls[inds_second]
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detections = self.init_track(dets, scores_keep, cls_keep, img)
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# Add newly detected tracklets to tracked_stracks
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unconfirmed = []
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tracked_stracks = [] # type: list[STrack]
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for track in self.tracked_stracks:
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if not track.is_activated:
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unconfirmed.append(track)
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else:
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tracked_stracks.append(track)
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# Step 2: First association, with high score detection boxes
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strack_pool = self.joint_stracks(tracked_stracks, self.lost_stracks)
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# Predict the current location with KF
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self.multi_predict(strack_pool)
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if hasattr(self, "gmc") and img is not None:
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warp = self.gmc.apply(img, dets)
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STrack.multi_gmc(strack_pool, warp)
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STrack.multi_gmc(unconfirmed, warp)
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dists = self.get_dists(strack_pool, detections)
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matches, u_track, u_detection = matching.linear_assignment(dists, thresh=self.args.match_thresh)
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for itracked, idet in matches:
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track = strack_pool[itracked]
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det = detections[idet]
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if track.state == TrackState.Tracked:
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track.update(det, self.frame_id)
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activated_stracks.append(track)
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else:
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track.re_activate(det, self.frame_id, new_id=False)
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refind_stracks.append(track)
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# Step 3: Second association, with low score detection boxes association the untrack to the low score detections
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detections_second = self.init_track(dets_second, scores_second, cls_second, img)
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r_tracked_stracks = [strack_pool[i] for i in u_track if strack_pool[i].state == TrackState.Tracked]
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# TODO
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dists = matching.iou_distance(r_tracked_stracks, detections_second)
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matches, u_track, u_detection_second = matching.linear_assignment(dists, thresh=0.5)
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for itracked, idet in matches:
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track = r_tracked_stracks[itracked]
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det = detections_second[idet]
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if track.state == TrackState.Tracked:
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track.update(det, self.frame_id)
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activated_stracks.append(track)
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else:
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track.re_activate(det, self.frame_id, new_id=False)
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refind_stracks.append(track)
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for it in u_track:
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track = r_tracked_stracks[it]
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if track.state != TrackState.Lost:
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track.mark_lost()
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lost_stracks.append(track)
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# Deal with unconfirmed tracks, usually tracks with only one beginning frame
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detections = [detections[i] for i in u_detection]
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dists = self.get_dists(unconfirmed, detections)
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matches, u_unconfirmed, u_detection = matching.linear_assignment(dists, thresh=0.7)
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for itracked, idet in matches:
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unconfirmed[itracked].update(detections[idet], self.frame_id)
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activated_stracks.append(unconfirmed[itracked])
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for it in u_unconfirmed:
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track = unconfirmed[it]
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track.mark_removed()
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removed_stracks.append(track)
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# Step 4: Init new stracks
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for inew in u_detection:
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track = detections[inew]
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if track.score < self.args.new_track_thresh:
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continue
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track.activate(self.kalman_filter, self.frame_id)
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activated_stracks.append(track)
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# Step 5: Update state
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for track in self.lost_stracks:
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if self.frame_id - track.end_frame > self.max_time_lost:
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track.mark_removed()
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removed_stracks.append(track)
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self.tracked_stracks = [t for t in self.tracked_stracks if t.state == TrackState.Tracked]
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self.tracked_stracks = self.joint_stracks(self.tracked_stracks, activated_stracks)
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self.tracked_stracks = self.joint_stracks(self.tracked_stracks, refind_stracks)
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self.lost_stracks = self.sub_stracks(self.lost_stracks, self.tracked_stracks)
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self.lost_stracks.extend(lost_stracks)
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self.lost_stracks = self.sub_stracks(self.lost_stracks, self.removed_stracks)
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self.tracked_stracks, self.lost_stracks = self.remove_duplicate_stracks(self.tracked_stracks, self.lost_stracks)
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self.removed_stracks.extend(removed_stracks)
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if len(self.removed_stracks) > 1000:
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self.removed_stracks = self.removed_stracks[-999:] # clip remove stracks to 1000 maximum
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return np.asarray([x.result for x in self.tracked_stracks if x.is_activated], dtype=np.float32)
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def get_kalmanfilter(self):
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"""Returns a Kalman filter object for tracking bounding boxes."""
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return KalmanFilterXYAH()
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def init_track(self, dets, scores, cls, img=None):
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"""Initialize object tracking with detections and scores using STrack algorithm."""
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return [STrack(xyxy, s, c) for (xyxy, s, c) in zip(dets, scores, cls)] if len(dets) else [] # detections
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def get_dists(self, tracks, detections):
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"""Calculates the distance between tracks and detections using IoU and fuses scores."""
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dists = matching.iou_distance(tracks, detections)
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# TODO: mot20
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# if not self.args.mot20:
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dists = matching.fuse_score(dists, detections)
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return dists
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def multi_predict(self, tracks):
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"""Returns the predicted tracks using the YOLOv8 network."""
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STrack.multi_predict(tracks)
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@staticmethod
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def reset_id():
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"""Resets the ID counter of STrack."""
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STrack.reset_id()
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def reset(self):
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"""Reset tracker."""
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self.tracked_stracks = [] # type: list[STrack]
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self.lost_stracks = [] # type: list[STrack]
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self.removed_stracks = [] # type: list[STrack]
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self.frame_id = 0
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self.kalman_filter = self.get_kalmanfilter()
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self.reset_id()
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@staticmethod
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def joint_stracks(tlista, tlistb):
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"""Combine two lists of stracks into a single one."""
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exists = {}
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res = []
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for t in tlista:
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exists[t.track_id] = 1
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res.append(t)
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for t in tlistb:
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tid = t.track_id
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if not exists.get(tid, 0):
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exists[tid] = 1
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res.append(t)
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return res
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@staticmethod
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def sub_stracks(tlista, tlistb):
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"""DEPRECATED CODE in https://github.com/ultralytics/ultralytics/pull/1890/
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stracks = {t.track_id: t for t in tlista}
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for t in tlistb:
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tid = t.track_id
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if stracks.get(tid, 0):
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del stracks[tid]
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return list(stracks.values())
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"""
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track_ids_b = {t.track_id for t in tlistb}
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return [t for t in tlista if t.track_id not in track_ids_b]
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@staticmethod
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def remove_duplicate_stracks(stracksa, stracksb):
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"""Remove duplicate stracks with non-maximum IoU distance."""
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pdist = matching.iou_distance(stracksa, stracksb)
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pairs = np.where(pdist < 0.15)
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dupa, dupb = [], []
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for p, q in zip(*pairs):
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timep = stracksa[p].frame_id - stracksa[p].start_frame
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timeq = stracksb[q].frame_id - stracksb[q].start_frame
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if timep > timeq:
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dupb.append(q)
|
|
else:
|
|
dupa.append(p)
|
|
resa = [t for i, t in enumerate(stracksa) if i not in dupa]
|
|
resb = [t for i, t in enumerate(stracksb) if i not in dupb]
|
|
return resa, resb
|