Q: - I can't open the webcam or video file.
A: Try re-install opencv-python with version >= 3.3.1.11 by
pip3 uninstall opencv_python
pip3 install opencv_python --user
Many people meet this problem at opencv/opencv#8471. The solution I use is
sudo cp <path to opencv source repo>/build/lib/python3/cv2.cpython-35m-x86_64-linux-gnu.so /usr/local/lib/python3.5/dist-packages/cv2/cv2.cpython-35m-x86_64-linux-gnu.so
The idea is to replace the cv2.so library provided by pypi with the one compiled from sources. You can check for more info at opencv/opencv#8471.
Q: - I can't open the webcam with the latest opencv-python
A: Check if your device is valid by
ls /dev/video*
Usually you can find video0, but if you have a device with other index like video3, you can run the program by
python3 webcam_demo.py --webcam 3 --outdir examples/res --vis
Q1: - I meet Killed when processing heavy task, like large videos or images with crowded persons.
A: Your system meets out of cpu memory and kills the program autoly. Please reduce the length of result buffer by setting the --qsize flag. By default length, free cpu memory over 70G+ is recommended in heavy task.
Q2: - I meet segmentation fault when processing heavy task, like large videos or images with crowded persons.
A: The parallelization module torch.multiprocessing is prone to shared memory leaks. Its garbage collection mechanism torch_shm_manager may cause segmentation fault under long-time heavy load. We found this issue when processing large videos with hundreds of persons. To avoid this issue, you can set --sp flag to use multi-thread instead, which sacrifices a little efficiency for more stablity.