Multi-Object Tracking with Ultralytics YOLO

Object tracking in the realm of video analytics is a critical task that not only identifies the location and class of objects within the frame but also maintains a unique ID for each detected object as the video progresses. The applications are limitless—ranging from surveillance and security to real-time sports analytics.

Why Choose Ultralytics YOLO for Object Tracking?

The output from Ultralytics trackers is consistent with standard object detection but has the added value of object IDs. This makes it easy to track objects in video streams and perform subsequent analytics. Here's why you should consider using Ultralytics YOLO for your object tracking needs:

• Efficiency: Process video streams in real-time without compromising accuracy.
• Flexibility: Supports multiple tracking algorithms and configurations.
• Ease of Use: Simple Python API and CLI options for quick integration and deployment.
• Customizability: Easy to use with custom trained YOLO models, allowing integration into domain-specific applications.

Watch: Object Detection and Tracking with Ultralytics YOLO.

Real-world Applications

Transportation	Retail	Aquaculture
Vehicle Tracking	People Tracking	Fish Tracking

Features at a Glance

Ultralytics YOLO extends its object detection features to provide robust and versatile object tracking:

• Real-Time Tracking: Seamlessly track objects in high-frame-rate videos.
• Multiple Tracker Support: Choose from a variety of established tracking algorithms.
• Customizable Tracker Configurations: Tailor the tracking algorithm to meet specific requirements by adjusting various parameters.

Available Trackers

Ultralytics YOLO supports the following tracking algorithms. They can be enabled by passing the relevant YAML configuration file such as tracker=tracker_type.yaml:

• BoT-SORT - Use botsort.yaml to enable this tracker.
• ByteTrack - Use bytetrack.yaml to enable this tracker.

The default tracker is BoT-SORT.

Tracking

To run the tracker on video streams, use a trained Detect, Segment or Pose model such as YOLO11n, YOLO11n-seg and YOLO11n-pose.

from ultralytics import YOLO

# Load an official or custom model
model = YOLO("yolo11n.pt")  # Load an official Detect model
model = YOLO("yolo11n-seg.pt")  # Load an official Segment model
model = YOLO("yolo11n-pose.pt")  # Load an official Pose model
model = YOLO("path/to/best.pt")  # Load a custom trained model

# Perform tracking with the model
results = model.track("https://youtu.be/LNwODJXcvt4", show=True)  # Tracking with default tracker
results = model.track("https://youtu.be/LNwODJXcvt4", show=True, tracker="bytetrack.yaml")  # with ByteTrack

# Perform tracking with various models using the command line interface
yolo track model=yolo11n.pt source="https://youtu.be/LNwODJXcvt4"      # Official Detect model
yolo track model=yolo11n-seg.pt source="https://youtu.be/LNwODJXcvt4"  # Official Segment model
yolo track model=yolo11n-pose.pt source="https://youtu.be/LNwODJXcvt4" # Official Pose model
yolo track model=path/to/best.pt source="https://youtu.be/LNwODJXcvt4" # Custom trained model

# Track using ByteTrack tracker
yolo track model=path/to/best.pt tracker="bytetrack.yaml"

As can be seen in the above usage, tracking is available for all Detect, Segment and Pose models run on videos or streaming sources.

Configuration

Tracking Arguments

Tracking configuration shares properties with Predict mode, such as conf, iou, and show. For further configurations, refer to the Predict model page.

from ultralytics import YOLO

# Configure the tracking parameters and run the tracker
model = YOLO("yolo11n.pt")
results = model.track(source="https://youtu.be/LNwODJXcvt4", conf=0.3, iou=0.5, show=True)

# Configure tracking parameters and run the tracker using the command line interface
yolo track model=yolo11n.pt source="https://youtu.be/LNwODJXcvt4" conf=0.3, iou=0.5 show

Tracker Selection

Ultralytics also allows you to use a modified tracker configuration file. To do this, simply make a copy of a tracker config file (for example, custom_tracker.yaml) from ultralytics/cfg/trackers and modify any configurations (except the tracker_type) as per your needs.

from ultralytics import YOLO

# Load the model and run the tracker with a custom configuration file
model = YOLO("yolo11n.pt")
results = model.track(source="https://youtu.be/LNwODJXcvt4", tracker="custom_tracker.yaml")

# Load the model and run the tracker with a custom configuration file using the command line interface
yolo track model=yolo11n.pt source="https://youtu.be/LNwODJXcvt4" tracker='custom_tracker.yaml'

Refer to Tracker Arguments section for a detailed description of each parameter.

Tracker Arguments

Some tracking behaviors can be fine-tuned by editing the YAML configuration files specific to each tracking algorithm. These files define parameters like thresholds, buffers, and matching logic:

• botsort.yaml
• bytetrack.yaml

The following table provides a description of each parameter:

Enabling Re-Identification (ReID)

By default, ReID is turned off to minimize performance overhead. Enabling it is simple—just set with_reid: True in the tracker configuration. You can also customize the model used for ReID, allowing you to trade off accuracy and speed depending on your use case:

• Native features (model: auto): This leverages features directly from the YOLO detector for ReID, adding minimal overhead. It's ideal when you need some level of ReID without significantly impacting performance. If the detector doesn't support native features, it automatically falls back to using yolo11n-cls.pt.
• YOLO classification models: You can explicitly set a classification model (e.g. yolo11n-cls.pt) for ReID feature extraction. This provides more discriminative embeddings, but introduces additional latency due to the extra inference step.

For better performance, especially when using a separate classification model for ReID, you can export it to a faster backend like TensorRT:

from torch import nn

from ultralytics import YOLO

# Load the classification model
model = YOLO("yolo11n-cls.pt")

# Add average pooling layer
head = model.model.model[-1]
pool = nn.Sequential(nn.AdaptiveAvgPool2d((1, 1)), nn.Flatten(start_dim=1))
pool.f, pool.i = head.f, head.i
model.model.model[-1] = pool

# Export to TensorRT
model.export(format="engine", half=True, dynamic=True, batch=32)

Once exported, you can point to the TensorRT model path in your tracker config, and it will be used for ReID during tracking.

Python Examples

Persisting Tracks Loop

Here is a Python script using OpenCV (cv2) and YOLO11 to run object tracking on video frames. This script still assumes you have already installed the necessary packages (opencv-python and ultralytics). The persist=True argument tells the tracker that the current image or frame is the next in a sequence and to expect tracks from the previous image in the current image.

import cv2

from ultralytics import YOLO

# Load the YOLO11 model
model = YOLO("yolo11n.pt")

# Open the video file
video_path = "path/to/video.mp4"
cap = cv2.VideoCapture(video_path)

# Loop through the video frames
while cap.isOpened():
    # Read a frame from the video
    success, frame = cap.read()

    if success:
        # Run YOLO11 tracking on the frame, persisting tracks between frames
        results = model.track(frame, persist=True)

        # Visualize the results on the frame
        annotated_frame = results[0].plot()

        # Display the annotated frame
        cv2.imshow("YOLO11 Tracking", annotated_frame)

        # Break the loop if 'q' is pressed
        if cv2.waitKey(1) & 0xFF == ord("q"):
            break
    else:
        # Break the loop if the end of the video is reached
        break

# Release the video capture object and close the display window
cap.release()
cv2.destroyAllWindows()

Please note the change from model(frame) to model.track(frame), which enables object tracking instead of simple detection. This modified script will run the tracker on each frame of the video, visualize the results, and display them in a window. The loop can be exited by pressing 'q'.

Plotting Tracks Over Time

Visualizing object tracks over consecutive frames can provide valuable insights into the movement patterns and behavior of detected objects within a video. With Ultralytics YOLO11, plotting these tracks is a seamless and efficient process.

In the following example, we demonstrate how to utilize YOLO11's tracking capabilities to plot the movement of detected objects across multiple video frames. This script involves opening a video file, reading it frame by frame, and utilizing the YOLO model to identify and track various objects. By retaining the center points of the detected bounding boxes and connecting them, we can draw lines that represent the paths followed by the tracked objects.

from collections import defaultdict

import cv2
import numpy as np

from ultralytics import YOLO

# Load the YOLO11 model
model = YOLO("yolo11n.pt")

# Open the video file
video_path = "path/to/video.mp4"
cap = cv2.VideoCapture(video_path)

# Store the track history
track_history = defaultdict(lambda: [])

# Loop through the video frames
while cap.isOpened():
    # Read a frame from the video
    success, frame = cap.read()

    if success:
        # Run YOLO11 tracking on the frame, persisting tracks between frames
        result = model.track(frame, persist=True)[0]

        # Get the boxes and track IDs
        if result.boxes and result.boxes.id is not None:
            boxes = result.boxes.xywh.cpu()
            track_ids = result.boxes.id.int().cpu().tolist()

            # Visualize the result on the frame
            frame = result.plot()

            # Plot the tracks
            for box, track_id in zip(boxes, track_ids):
                x, y, w, h = box
                track = track_history[track_id]
                track.append((float(x), float(y)))  # x, y center point
                if len(track) > 30:  # retain 30 tracks for 30 frames
                    track.pop(0)

                # Draw the tracking lines
                points = np.hstack(track).astype(np.int32).reshape((-1, 1, 2))
                cv2.polylines(frame, [points], isClosed=False, color=(230, 230, 230), thickness=10)

        # Display the annotated frame
        cv2.imshow("YOLO11 Tracking", frame)

        # Break the loop if 'q' is pressed
        if cv2.waitKey(1) & 0xFF == ord("q"):
            break
    else:
        # Break the loop if the end of the video is reached
        break

# Release the video capture object and close the display window
cap.release()
cv2.destroyAllWindows()

Multithreaded Tracking

Multithreaded tracking provides the capability to run object tracking on multiple video streams simultaneously. This is particularly useful when handling multiple video inputs, such as from multiple surveillance cameras, where concurrent processing can greatly enhance efficiency and performance.

In the provided Python script, we make use of Python's threading module to run multiple instances of the tracker concurrently. Each thread is responsible for running the tracker on one video file, and all the threads run simultaneously in the background.

To ensure that each thread receives the correct parameters (the video file, the model to use and the file index), we define a function run_tracker_in_thread that accepts these parameters and contains the main tracking loop. This function reads the video frame by frame, runs the tracker, and displays the results.

Two different models are used in this example: yolo11n.pt and yolo11n-seg.pt, each tracking objects in a different video file. The video files are specified in SOURCES.

The daemon=True parameter in threading.Thread means that these threads will be closed as soon as the main program finishes. We then start the threads with start() and use join() to make the main thread wait until both tracker threads have finished.

Finally, after all threads have completed their task, the windows displaying the results are closed using cv2.destroyAllWindows().

import threading

import cv2

from ultralytics import YOLO

# Define model names and video sources
MODEL_NAMES = ["yolo11n.pt", "yolo11n-seg.pt"]
SOURCES = ["path/to/video.mp4", "0"]  # local video, 0 for webcam


def run_tracker_in_thread(model_name, filename):
    """
    Run YOLO tracker in its own thread for concurrent processing.

    Args:
        model_name (str): The YOLO11 model object.
        filename (str): The path to the video file or the identifier for the webcam/external camera source.
    """
    model = YOLO(model_name)
    results = model.track(filename, save=True, stream=True)
    for r in results:
        pass


# Create and start tracker threads using a for loop
tracker_threads = []
for video_file, model_name in zip(SOURCES, MODEL_NAMES):
    thread = threading.Thread(target=run_tracker_in_thread, args=(model_name, video_file), daemon=True)
    tracker_threads.append(thread)
    thread.start()

# Wait for all tracker threads to finish
for thread in tracker_threads:
    thread.join()

# Clean up and close windows
cv2.destroyAllWindows()

This example can easily be extended to handle more video files and models by creating more threads and applying the same methodology.

Contribute New Trackers

Are you proficient in multi-object tracking and have successfully implemented or adapted a tracking algorithm with Ultralytics YOLO? We invite you to contribute to our Trackers section in ultralytics/cfg/trackers! Your real-world applications and solutions could be invaluable for users working on tracking tasks.

By contributing to this section, you help expand the scope of tracking solutions available within the Ultralytics YOLO framework, adding another layer of functionality and utility for the community.

To initiate your contribution, please refer to our Contributing Guide for comprehensive instructions on submitting a Pull Request (PR) 🛠️. We are excited to see what you bring to the table!

Together, let's enhance the tracking capabilities of the Ultralytics YOLO ecosystem 🙏!

FAQ

What is Multi-Object Tracking and how does Ultralytics YOLO support it?

Multi-object tracking in video analytics involves both identifying objects and maintaining a unique ID for each detected object across video frames. Ultralytics YOLO supports this by providing real-time tracking along with object IDs, facilitating tasks such as security surveillance and sports analytics. The system uses trackers like BoT-SORT and ByteTrack, which can be configured via YAML files.

How do I configure a custom tracker for Ultralytics YOLO?

You can configure a custom tracker by copying an existing tracker configuration file (e.g., custom_tracker.yaml) from the Ultralytics tracker configuration directory and modifying parameters as needed, except for the tracker_type. Use this file in your tracking model like so:

from ultralytics import YOLO

model = YOLO("yolo11n.pt")
results = model.track(source="https://youtu.be/LNwODJXcvt4", tracker="custom_tracker.yaml")

yolo track model=yolo11n.pt source="https://youtu.be/LNwODJXcvt4" tracker='custom_tracker.yaml'

How can I run object tracking on multiple video streams simultaneously?

To run object tracking on multiple video streams simultaneously, you can use Python's threading module. Each thread will handle a separate video stream. Here's an example of how you can set this up:

import threading

import cv2

from ultralytics import YOLO

# Define model names and video sources
MODEL_NAMES = ["yolo11n.pt", "yolo11n-seg.pt"]
SOURCES = ["path/to/video.mp4", "0"]  # local video, 0 for webcam


def run_tracker_in_thread(model_name, filename):
    """
    Run YOLO tracker in its own thread for concurrent processing.

    Args:
        model_name (str): The YOLO11 model object.
        filename (str): The path to the video file or the identifier for the webcam/external camera source.
    """
    model = YOLO(model_name)
    results = model.track(filename, save=True, stream=True)
    for r in results:
        pass


# Create and start tracker threads using a for loop
tracker_threads = []
for video_file, model_name in zip(SOURCES, MODEL_NAMES):
    thread = threading.Thread(target=run_tracker_in_thread, args=(model_name, video_file), daemon=True)
    tracker_threads.append(thread)
    thread.start()

# Wait for all tracker threads to finish
for thread in tracker_threads:
    thread.join()

# Clean up and close windows
cv2.destroyAllWindows()

What are the real-world applications of multi-object tracking with Ultralytics YOLO?

Multi-object tracking with Ultralytics YOLO has numerous applications, including:

• Transportation: Vehicle tracking for traffic management and autonomous driving.
• Retail: People tracking for in-store analytics and security.
• Aquaculture: Fish tracking for monitoring aquatic environments.
• Sports Analytics: Tracking players and equipment for performance analysis.
• Security Systems: Monitoring suspicious activities and creating security alarms.

These applications benefit from Ultralytics YOLO's ability to process high-frame-rate videos in real time with exceptional accuracy.

How can I visualize object tracks over multiple video frames with Ultralytics YOLO?

To visualize object tracks over multiple video frames, you can use the YOLO model's tracking features along with OpenCV to draw the paths of detected objects. Here's an example script that demonstrates this:

from collections import defaultdict

import cv2
import numpy as np

from ultralytics import YOLO

model = YOLO("yolo11n.pt")
video_path = "path/to/video.mp4"
cap = cv2.VideoCapture(video_path)
track_history = defaultdict(lambda: [])

while cap.isOpened():
    success, frame = cap.read()
    if success:
        results = model.track(frame, persist=True)
        boxes = results[0].boxes.xywh.cpu()
        track_ids = results[0].boxes.id.int().cpu().tolist()
        annotated_frame = results[0].plot()
        for box, track_id in zip(boxes, track_ids):
            x, y, w, h = box
            track = track_history[track_id]
            track.append((float(x), float(y)))
            if len(track) > 30:
                track.pop(0)
            points = np.hstack(track).astype(np.int32).reshape((-1, 1, 2))
            cv2.polylines(annotated_frame, [points], isClosed=False, color=(230, 230, 230), thickness=10)
        cv2.imshow("YOLO11 Tracking", annotated_frame)
        if cv2.waitKey(1) & 0xFF == ord("q"):
            break
    else:
        break
cap.release()
cv2.destroyAllWindows()

This script will plot the tracking lines showing the movement paths of the tracked objects over time, providing valuable insights into object behavior and patterns.

📅 Created 1 year ago ✏️ Updated 13 days ago

Comments