GStreamer API in OpenCV: autovideosink vs appsink

Question

The following Gstreamer Receiver command works fine when I run it on the terminal.

gst-launch-1.0 -v udpsrc port=5004 ! 'application/x-rtp,payload=96,encoding-name=H264' ! rtpjitterbuffer mode=1 ! rtph264depay ! h264parse ! decodebin ! videoconvert ! autovideosink

I need to do capture these frames and do some processing using OpenCV's Gstreamer API. I used the exact pipeline in my C++ code but the VideoCapture is failing to start. The code is as follows:

#include <opencv2/opencv.hpp>
#include <opencv2/videoio.hpp>
using namespace cv;

#include <iostream>
using namespace std;

int main()
{
    VideoCapture cap("udpsrc port=5004 ! application/x-rtp,payload=96,encoding-name=H264 ! rtpjitterbuffer mode=1 ! rtph264depay ! h264parse ! decodebin ! videoconvert ! autovideosink", CAP_GSTREAMER);
    
    if (!cap.isOpened()) {
        cerr <<"VideoCapture not opened"<<endl;
        exit(-1);
    }
    
    while (true) {

        Mat frame;

        cap.read(frame);

        imshow("receiver", frame);

        //  Process the frame.

        if (waitKey(1) == 27) {
            break;
        }
    }

    return 0;
}

When I try to compile and run I receive:

(Receiver_Teal:2292): GStreamer-CRITICAL **: gst_element_get_state: assertion 'GST_IS_ELEMENT (element)' failed

VideoCapture not opened

wschopohl wschopohl · Accepted Answer · 2019-10-23T16:06:11

Try replacing the autovideosink at the end with appsink

VideoCapture cap("udpsrc port=5004 ! application/x-rtp,payload=96,encoding-name=H264 ! rtpjitterbuffer mode=1 ! rtph264depay ! h264parse ! decodebin ! videoconvert ! appsink", CAP_GSTREAMER);

GStreamer API in OpenCV: autovideosink vs appsink

1 Answers