Live Streaming over USB on Ubuntu and Linux, NVIDIA Jetson

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I have the lag with the Python cv2 lib. However, if I run vlc on /dev/video0 on the Jetson nano, there is no lag. Thus, I suspect the lag might be related to the simple python test script. I’m not sure. Just confirming that my situation is the same as yours. Thanks for the update and congratulations on making so much progress, so quickly. :slight_smile:

In addition to vlc, I tested the v4l2src with gst-launch and the latency is low. I haven’t looked at the cv2 lib yet.

gst-launch-1.0 -v v4l2src ! videoconvert ! videoscale ! video/x-raw,width=1000,height=500  ! xvimagesink

Devices on Nano.

$ v4l2-ctl --list-devices
Dummy video device (0x0000) (platform:v4l2loopback-000):
	/dev/video0

Tested lower latency with OpenCV using cv2 Python module.

This one just resizes the video, but it does show the processing with OpenCV is usuable, though slower than with C.

import cv2

cap = cv2.VideoCapture(0)

# Check if the webcam is opened correctly
if not cap.isOpened():
    raise IOError("Cannot open webcam")

while True:
    ret, frame = cap.read()
    frame = cv2.resize(frame, None, fx=0.25, fy=0.25, interpolation=cv2.INTER_AREA)
    cv2.imshow('Input', frame)

    c = cv2.waitKey(1)
    if c == 27:
        break

cap.release()
cv2.destroyAllWindows()

compare to gst-launch using v4l2src. You can adjust the size of the video window to do the same size test.

gst-launch-1.0 -v v4l2src ! videoconvert ! videoscale ! video/x-raw,width=1000,height=500  ! xvimagesink
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