OpenCV3.0+Ubuntu16调用VideoCapture遇GStreamer关键错误

Hey there, let's work through this camera connection issue you're hitting. That GStreamer critical error you're seeing (gst_element_get_state: assertion 'GST_IS_ELEMENT (element)' failed) typically stems from mismatched OpenCV-GStreamer integration or system-level camera access problems. Here are the actionable steps to fix it:

1. Verify Camera Hardware Permissions #

First, make sure your user account has access to the camera device:

• Run this command to check device permissions:

  ls -l /dev/video*
  

• If your username isn't listed in the group column (usually video), add yourself to the group:

  sudo usermod -aG video $USER
  

• Log out and back in for the permission changes to take effect.

2. Recompile OpenCV with GStreamer Support #

OpenCV 3.0 often doesn't enable GStreamer support by default during installation on Ubuntu 16.04. You'll need to recompile OpenCV with GStreamer enabled:

Step 1: Install GStreamer Dependencies #

sudo apt-get update
sudo apt-get install libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev gstreamer1.0-plugins-good gstreamer1.0-plugins-bad gstreamer1.0-plugins-ugly

Step 2: Reconfigure OpenCV Build #

Navigate to your OpenCV build directory (create one if you don't have it) and run:

cmake -D CMAKE_BUILD_TYPE=Release \
      -D CMAKE_INSTALL_PREFIX=/usr/local \
      -D WITH_GSTREAMER=ON \
      -D WITH_GSTREAMER_0_10=OFF \
      ..

Step 3: Recompile and Install #

make -j$(nproc)  # Uses all CPU cores for faster build
sudo make install

3. Force a Specific Video Capture Backend #

Sometimes the default backend selection fails. Try explicitly using the V4L2 backend in your code:

#include <opencv2/videoio.hpp>

using namespace cv;

int main() {
    // Force V4L2 backend instead of relying on auto-detection
    VideoCapture cap(0, CAP_V4L2);
    if (!cap.isOpened()) {
        printf("Failed to open camera!\n");
        return -1;
    }
    // Rest of your code...
    return 0;
}

Alternatively, you can use a direct GStreamer pipeline for more control:

VideoCapture cap("v4l2src device=/dev/video0 ! videoconvert ! appsink", CAP_GSTREAMER);

4. Check for Conflicting Processes #

Make sure no other application is using the camera:

lsof /dev/video0

If any processes are listed, kill them with sudo kill <PID> and try again.

5. Validate Camera Hardware Functionality #

Rule out hardware issues by testing with a native Linux tool:

• Install and run Cheese:

  sudo apt-get install cheese
  cheese
  

Or use FFplay:

ffplay /dev/video0

If these tools can't access the camera either, you may have a hardware or driver problem.

内容的提问来源于stack exchange，提问作者Maxime Refield