DevHeads IoT Integration Server•3mo ago

USB Webcam Not Working on Jetson Nano for OpenCV/TensorFlow Object Detection

Hello guys, I am trying to set up a USB webcam on my NVIDIA Jetson Nano to perform real-time video analytics using OpenCV and TensorFlow, I have installed OpenCV and TensorFlow on Ubuntu, connected a USB webcam to the Jetson Nano, wrote a Python script to capture video frames and perform object detection. But I keep getting the error

[ WARN:0] global /tmp/pip-req-build-1234abcd/opencv/modules/videoio/src/cap_v4l.cpp (890) open VIDEOIO(V4L2:/dev/video0): can't open camera by index

[ WARN:0] global /tmp/pip-req-build-1234abcd/opencv/modules/videoio/src/cap_v4l.cpp (890) open VIDEOIO(V4L2:/dev/video0): can't open camera by index

This is my code snippet 👇

import cv2
import tensorflow as tf

# Load the pre-trained object detection model
model = tf.saved_model.load('ssd_mobilenet_v2/saved_model')

# Open the USB webcam
cap = cv2.VideoCapture(0)

while cap.isOpened():
    ret, frame = cap.read()
    if not ret:
        print("Failed to capture image")
        break
    
    # Preprocess the frame for the model
    input_tensor = tf.convert_to_tensor(frame)
    input_tensor = input_tensor[tf.newaxis, ...]

    # Perform object detection
    detections = model(input_tensor)

    # Display the frame
    cv2.imshow('Frame', frame)
    
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

import cv2
import tensorflow as tf

# Load the pre-trained object detection model
model = tf.saved_model.load('ssd_mobilenet_v2/saved_model')

# Open the USB webcam
cap = cv2.VideoCapture(0)

while cap.isOpened():
    ret, frame = cap.read()
    if not ret:
        print("Failed to capture image")
        break
    
    # Preprocess the frame for the model
    input_tensor = tf.convert_to_tensor(frame)
    input_tensor = input_tensor[tf.newaxis, ...]

    # Perform object detection
    detections = model(input_tensor)

    # Display the frame
    cv2.imshow('Frame', frame)
    
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

@Middleware & OS @Helper

Solution:

v4l2-ctl --list-devices
v4l2-ctl --device=/dev/video0 --stream-mmap=3 --stream-count=10

v4l2-ctl --list-devices
v4l2-ctl --device=/dev/video0 --stream-mmap=3 --stream-count=10

If the above steps don't help, try running a simple OpenCV script to verify if OpenCV can access the camera: ...

Jump to solution

8 Replies

RED HAT•3mo ago

whatsup @Enthernet Code , It seems like there’s an issue with the camera index or how the camera is being accessed. Make sure that /dev/video0 is the correct device for your USB webcam. You can list all video devices connected to your Jetson Nano using

ls /dev/video*

ls /dev/video*

This will show you all available video devices. If your webcam is not listed as /dev/video0, you might need to change the index in your cv2.VideoCapture(0) line to match the correct device.

Enthernet Code•3mo ago

I have checked it using the code it's listed there

RED HAT•3mo ago

Also, check the permissions for your video device. Sometimes, access issues can cause this kind of error. You can change the permissions by running

sudo chmod 777 /dev/video0

sudo chmod 777 /dev/video0

although i wont recommend this for production enviroment

Enthernet Code•3mo ago

Like this?? sudo user mod -aG video enthernet

RED HAT•3mo ago

Then, log out and log back in for the changes to take effect.

Enthernet Code•3mo ago

Okay

Dark AI•3mo ago

hello, @Enthernet Code Make sure you have all the necessary dependencies installed for video capture. You can try installing v4l-utils which provides tools for video device querying and configuration:

sudo apt-get install v4l-utils

sudo apt-get install v4l-utils

You can also try to capture video using v4l2-ctl to ensure the camera is working correctly:

Solution

Dark AI•3mo ago

v4l2-ctl --list-devices
v4l2-ctl --device=/dev/video0 --stream-mmap=3 --stream-count=10

v4l2-ctl --list-devices
v4l2-ctl --device=/dev/video0 --stream-mmap=3 --stream-count=10

If the above steps don't help, try running a simple OpenCV script to verify if OpenCV can access the camera:

import cv2

cap = cv2.VideoCapture(0)

if not cap.isOpened():
    print("Cannot open camera")
    exit()

while True:
    ret, frame = cap.read()
    if not ret:
        print("Can't receive frame (stream end?). Exiting ...")
        break
    cv2.imshow('frame', frame)
    if cv2.waitKey(1) == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

import cv2

cap = cv2.VideoCapture(0)

if not cap.isOpened():
    print("Cannot open camera")
    exit()

while True:
    ret, frame = cap.read()
    if not ret:
        print("Can't receive frame (stream end?). Exiting ...")
        break
    cv2.imshow('frame', frame)
    if cv2.waitKey(1) == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

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USB Webcam Not Working on Jetson Nano for OpenCV/TensorFlow Object Detection