OpenCV VideoCapture() capture freezes when GStreamer is enabled

Autonomous Machines Jetson & Embedded Systems Jetson Xavier NX
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1

I uses the following sample code to capture RTP stream from IP camera. But it freezes.
string gstStr = “rtspsrc location=rtsp://192.168.50.253:8554/test latency=200 ! rtph264depay ! h264parse ! omxh264dec ! nvvidconv ! video/x-raw, format=BGRx ! videoconvert ! appsink”;

VidecoCapture capture(gstStr, CAP_GSTREAMER);
Mat captureFrame;
capture.read(captureFrame);

3

Hi,
Please check if you can launch the pipeline:

gst-launch-1.0 rtspsrc location=rtsp://192.168.50.253:8554/test latency=200 ! rtph264depay ! nvv4l2decoder ! nvoverlaysink

If yes, please try the python sample:

import sys
import cv2

def read_cam():
    cap = cv2.VideoCapture("rtspsrc location=rtsp://192.168.50.253:8554/test latency=200 ! rtph264depay ! nvv4l2decoder ! nvvidconv ! video/x-raw, format=(string)BGRx ! videoconvert ! video/x-raw,format=BGR ! appsink ")
    if cap.isOpened():
        cv2.namedWindow("demo", cv2.WINDOW_AUTOSIZE)
        while True:
            ret_val, img = cap.read();
            cv2.imshow('demo',img)
            cv2.waitKey(10)
    else:
     print "rtsp open failed"

    cv2.destroyAllWindows()


if __name__ == '__main__':
    read_cam()
4

Thanks for your reply! I can launch the following pipeline on NX.
gst-launch-1.0 rtspsrc location=rtsp://192.168.50.253:8554/test latency=200 ! rtph264depay ! nvv4l2decoder ! nvoverlaysink

I have replaced GStreamer command according your suggestion and doing overnight testing to see if capture frame freezing issue is solved .

5

VideoCapture still freezes with the following command.
"rtspsrc location=rtsp://192.168.50.253:8554/test latency=200 ! rtph264depay ! nvv4l2decoder ! nvvidconv ! video/x-raw, format=(string)BGRx ! videoconvert ! video/x-raw,format=BGR ! appsink "

6

Hi,
We launch a RTSP server:

$ ./test-launch "videotestsrc pattern=18 ! video/x-raw,width=1280,height=720 ! nvvidconv ! nvv4l2h264enc ! h264parse ! rtph264pay name=pay0 pt=96"

And don’t hit video freeze in running the python sample. Probably the issue is because your RTSP source is not stable?

7

OpenCV VideoCapture without GStreamer enabled doesn’t have freezing issue.
VidecoCapture capture(“rtsp://192.168.50.253:8554/test”);
Mat captureFrame;
capture.read(captureFrame);

8

Hi,
We would suggest use gstreamer pipeline to enable hardware decoding.

If software decoder is good enough in your usecase, you may try: