Hi
The delay may be from network or source. You may run the command to check glass-to-glass latency first:
gst-launch-1.0 v4l2src device=/dev/video1 io-mode=2 ! image/jpeg,width=1280,height=720,framerate=30/1 ! jpegparse ! nvv4l2decoder mjpeg=1 ! nvoverlaysink
For launching audio source, please refer to
Live streaming cam usb - #4 by DaneLLL
test-launch is a sample in native gstreamer package. For further question about it, please go to gstreamer forum