Open videocapture freeze with no device (gstreamer)

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Hi,

It works fine with the device exist, but freeze with no device. I would like it can return to fail when connecting fail. Have any suggestions?

Thanks

This is my sample to open the camera by videcocapture: bRes &= cap->open("udpsrc port=5003 ! application/x-rtp, encoding-name=JPEG,payload=26 ! rtpjpegdepay ! jpegdec ! videoconvert ! appsink", cv::CAP_GSTREAMER);