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Re-identification

In computer vision based multi object tracking, re-identification (ReID) can be used for addressing the issue of objects temporary being occluded or leaving the scene. Objects being tracked can be temporarily hidden by other objects or move out of the camera's view, making consistent tracking challenging. Additionally, variations in pose, orientation, and lighting conditions from one frame to another can further complicate the tracking.

When an object temporary disappears and then reappears in a new frame, the tracker may fail to recognize it and start tracking it as a new object initiating a new track, leading to errors and inconsistencies. This misidentification disrupts the continuity of tracking information.

ReID aims to resolve this by matching the features of the reappearing object with those of the previously tracked objects, regardless of changes in location, orientation, or lighting. This approach improves the trackers ability to maintain consistent tracking information for the object throughout the video.

The image below illustrates how a ReID can occur in a scene, and how the tracker communicates it. We observe that the human track first has ID 1, then, as it leaves the scene and comes back, the tracker initiates a new track with ID 2 for the same human. After some time however, ReID triggers and is communicated with a Rename event stating that the track with ID 2 is actually tracking the same object as the track with ID 1. Rename implies that the track with ID 2 may be incorporated into the track with ID 1, the track with ID 2 is terminated and tracking of that object will continue using the track with ID 1.

ReID

In AXIS Scene Metadata, the way ReID is represented depends on the data framing. With ObjectTrack framing, local re-identification is implicit: each ObjectTrack contains consolidated data for one object across its scene lifespan, including any re-identifications.

When consuming data via Frame framing, re-identification events are indicated using the Rename event property on the Frame type.