OpenCV videostream doesn't work with imx219 on Jetson Nano

[KonradC]

Hi,
I want to use an ArduCam Camarray Hat with four imx219 Cameras with a Jetson Nano. Because I want to “analyze” the video-stream and run some code for object detection and stuff like that, I tried to get the video-stream with OpenCV (I installed it via “sudo apt install python3-opencv”).
First, I tested the cameras with “nvgstcapture-1.0” and it ran without problems.
“gst-launch-1.0 nvarguscamerasrc ! ‘video/x-raw(memory:NVMM), width=(int)1920, height=(int)1080,format=(string)NV12, framerate=(fraction)30/1’ ! nvoverlaysink” runs without problems too, but the code: OpenCV Video Capture with GStreamer doesn't work on ROS-melodic - #3 by DaneLLL says, “camera open failed”. Then I found this Python-code for OpenCV:

import cv2

cap = cv2.VideoCapture(0)

if (cap.isOpened()== False): 
  print("Error opening video stream or file")

while(cap.isOpened()):
  ret, frame = cap.read()
  if ret == True:

    cv2.imshow('Frame',frame)

    if cv2.waitKey(25) & 0xFF == ord('q'):
      break

  else: 
    break

cap.release()

cv2.destroyAllWindows()

But I get this Error:

select timeout
select timeout
OpenCV Error: Assertion failed (total() == 0 || data != NULL) in Mat, file /build/opencv-XDqSFW/opencv-3.2.0+dfsg/modules/core/include/opencv2/core/mat.inl.hpp, line 431
Traceback (most recent call last):
  File "/home/konrad/Documents/Folder/Cameratest2.py", line 15, in <module>
    ret, frame = cap.read()
cv2.error: /build/opencv-XDqSFW/opencv-3.2.0+dfsg/modules/core/include/opencv2/core/mat.inl.hpp:431: error: (-215) total() == 0 || data != NULL in function Mat

Because I thought the Camarray Hat may cause the issue, I tried the same code with a Raspberry Pi v2.1 imx219 camera. With it, I don’t get the error, but the output is just green (what is maybe the standard output of gstreamer).
Do you know how I can solve my problem?
Thanks in advance, Konrad

[DaneLLL]

Hi,
You would need to run a gstreamer pipeline in cv2.VideoCapture() to use nvarguscamerasrc plugin. Please try this sample:
OpenCV Video Capture with GStreamer doesn't work on ROS-melodic - #3 by DaneLLL

[KonradC]

Thank you for the fast response. I’ll try it tomorrow.
Konrad

[KonradC]

Hi,
I tried it and it looks like OpenCV is causing the problem, because gst-launch runns but in the program something must go wrong at “cap = cv2.VideoCapture…”. So it can’t open the camera. But I think it’s a topic for the Opencv forum isn’t it?

[DaneLLL]

Hi,
Seems like you don’t use the OpenCV 4.1.1 package installed through SDKManager. The log shows 3.2 and it probably doesn’t enable gstreamer. Please check if you can re-install the 4.1.1 one.

[KonradC]

Hi,
thank you for your answer. I installed Opencv 4.5 and now your code works fine. I needed so long for the response because I had some problems with the installing.
Best regards,
Konrad