Hi,
This string should work also:
std::string gst_str = "v4l2src io-mode=2 ! image/jpeg,width=1280,height=480,framerate=60/1 ! jpegparse ! nvv4l2decoder mjpeg=1 ! nvvidconv ! video/x-raw,format=RGBA ! videoconvert ! video/x-raw,format=BGR ! appsink "
May give it a try.