Raspberry Pi4 error capturing image with OpenCV, image comes half green

Question

I am using a common logitech webcam with OpenCV. When I was using my RPI3 I had no trouble, but I wanted to improve my system so I bought a RPI4.

Upon setting up my system with RPI4 using raspian buster I've started getting:

VIDIOC_DQBUF: Resource temporarily unavailable

After I saw this question here I tried:

pi@raspberrypi:~ $ sudo rmmod uvcvideo
pi@raspberrypi:~ $ sudo modprobe uvcvideo nodrop=1 timeout=5000 quirks=0x80

Now my image comes like this:

The upper part of the image is ok, it's night time and it is pointing to my backyard, however I don't know how to solve the green part problem.

Any ideas?

Answer 1

I've managed to do it!!!

This is really needed:

pi@raspberrypi:~ $ sudo rmmod uvcvideo
pi@raspberrypi:~ $ sudo modprobe uvcvideo nodrop=1 timeout=5000 quirks=0x80

But also, I had to set my webcam FPS prop to a low value.

0. CV_CAP_PROP_POS_MSEC Current position of the video file in milliseconds.
1. CV_CAP_PROP_POS_FRAMES 0-based index of the frame to be decoded/captured next.
2. CV_CAP_PROP_POS_AVI_RATIO Relative position of the video file
3. CV_CAP_PROP_FRAME_WIDTH Width of the frames in the video stream.
4. CV_CAP_PROP_FRAME_HEIGHT Height of the frames in the video stream.
5. CV_CAP_PROP_FPS Frame rate.
6. CV_CAP_PROP_FOURCC 4-character code of codec.
7. CV_CAP_PROP_FRAME_COUNT Number of frames in the video file.
8. CV_CAP_PROP_FORMAT Format of the Mat objects returned by retrieve() .
9. CV_CAP_PROP_MODE Backend-specific value indicating the current capture mode.
10. CV_CAP_PROP_BRIGHTNESS Brightness of the image (only for cameras).
11. CV_CAP_PROP_CONTRAST Contrast of the image (only for cameras).
12. CV_CAP_PROP_SATURATION Saturation of the image (only for cameras).
13. CV_CAP_PROP_HUE Hue of the image (only for cameras).
14. CV_CAP_PROP_GAIN Gain of the image (only for cameras).
15. CV_CAP_PROP_EXPOSURE Exposure (only for cameras).
16. CV_CAP_PROP_CONVERT_RGB Boolean flags indicating whether images should be converted to RGB.
17. CV_CAP_PROP_WHITE_BALANCE Currently unsupported
18. CV_CAP_PROP_RECTIFICATION Rectification

Before starting to read the cam just do:

cam.set(cv2.CAP_PROP_FPS, 10)

All set! :)