It is a C++ wrapper for V4L2 mofified from https://github.com/mpromonet/libv4l2cpp by mpromonet. I added more prints and solved problem which is a video device may have rather than one video resource.And main keypoints I added was opencv Mat BGR format surport.

• liblog4cpp5-dev (optional)

• create a V4L2 Capture interface using MMAP interface:

    V4L2DeviceParameters param("/dev/video0", V4L2_PIX_FMT_*, width, height, fps, input_index, verbose);
    V4l2Capture* videoCapture = V4l2Capture::create(param, V4l2Access::IOTYPE_MMAP);
  

• data are available :

    timeval timeout; 
    bool isReadable = (videoCapture->isReadable(&timeout) == 1);
  

• read data :

    size_t nb = videoCapture->read(buffer, bufferSize);
  

• To create a V4L2 Output interface using MMAP interface:

    V4L2DeviceParameters param("/dev/video0", V4L2_PIX_FMT_*, width, height, fps, input_index , verbose);
    V4l2Output* videoOutput = V4l2Output::create(param, V4l2Access::IOTYPE_MMAP);
  

• data could be written :

    timeval timeout; 
    bool isWritable = (videoOutput->isWritable(&timeout) == 1);
  

• write data :

    size_t nb = videoOutput->write(buffer, bufferSize);