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Sample - Object tracking example usage on DepthAI

Demo

Source code

import cv2
import depthai

device = depthai.Device('', False)

p = device.create_pipeline(config={
    "streams": ["previewout", "object_tracker"],
    "ai": {
        "blob_file": "/path/to/depthai/resources/nn/mobilenet-ssd/mobilenet-ssd.blob",
        "blob_file_config": "/path/to/depthai/resources/nn/mobilenet-ssd/mobilenet-ssd.json"
    },
    'ot': {
        'max_tracklets': 20,
        'confidence_threshold': 0.5,
    },
})

if p is None:
    raise RuntimeError("Error initializing pipelne")

labels = ["background", "aeroplane", "bicycle", "bird", "boat", "bottle", "bus", "car", "cat", "chair", "cow", "diningtable", "dog", "horse", "motorbike", "person", "pottedplant", "sheep", "sofa", "train", "tvmonitor"]
tracklets = None

while True:
    for packet in p.get_available_data_packets():
        if packet.stream_name == 'object_tracker':
            tracklets = packet.getObjectTracker()
        elif packet.stream_name == 'previewout':
            data = packet.getData()
            data0 = data[0, :, :]
            data1 = data[1, :, :]
            data2 = data[2, :, :]
            frame = cv2.merge([data0, data1, data2])

            traklets_nr = tracklets.getNrTracklets() if tracklets is not None else 0

            for i in range(traklets_nr):
                tracklet = tracklets.getTracklet(i)
                left = tracklet.getLeftCoord()
                top = tracklet.getTopCoord()
                right = tracklet.getRightCoord()
                bottom = tracklet.getBottomCoord()
                tracklet_label = labels[tracklet.getLabel()]

                cv2.rectangle(frame, (left, top), (right, bottom), (255, 0, 0))

                middle_pt = (int(left + (right - left) / 2), int(top + (bottom - top) / 2))
                cv2.circle(frame, middle_pt, 0, (255, 0, 0), -1)
                cv2.putText(frame, f"ID {tracklet.getId()}", middle_pt, cv2.FONT_HERSHEY_SIMPLEX, 0.5, (255, 0, 0), 2)

                cv2.putText(frame, tracklet_label, (left, bottom - 40), cv2.FONT_HERSHEY_SIMPLEX, 0.5, (255, 0, 0), 2)
                cv2.putText(frame, tracklet.getStatus(), (left, bottom - 20), cv2.FONT_HERSHEY_SIMPLEX, 0.5, (255, 0, 0), 2)

            cv2.imshow('previewout', frame)

    if cv2.waitKey(1) == ord('q'):
        break

del p
del device

Explanation

DepthAI is capable of doing object tracking from the device itself, so you don’t have to write your own custom code for it.

First, we change the method for retrieving the data packets from the pipeline, as we’re not using metaout stream

    for packet in p.get_available_data_packets():

Next up, if the packet is from stream object_tracker we use a special method available only in packets from this stream to obtain tracklets object - this method will throw an error if used on another stream

        if packet.stream_name == 'object_tracker':
            tracklets = packet.getObjectTracker()

Next up, we’re obtaining all tracklet info for further processing

                tracklet = tracklets.getTracklet(i)
                left = tracklet.getLeftCoord()
                top = tracklet.getTopCoord()
                right = tracklet.getRightCoord()
                bottom = tracklet.getBottomCoord()
                tracklet_label = labels[tracklet.getLabel()]

And rest of the processing is only for visual representation of the tracking objects, which you can skip if you want to use object tracker in different way

Do you have any questions/suggestions? Feel free to get in touch and let us know!