Hi,
Do you run gstreamer command in cv2.VideoCapture()? Generally we run like this:
V4l2src using OpenCV Gstreamer is not working in Jetson Xavier NX - #3 by DaneLLL
And for using CUDA filters, we suggest run gstreamer pipeline and map NvBuffer to cv::gpu::gpuMat. Please check this sample:
Nano not using GPU with gstreamer/python. Slow FPS, dropped frames - #8 by DaneLLL