Running gst-launch-1.0 from serial console

[Ranran]

Hello,

We need to start gstreamer from serial console , and see the video on
the display output (regular hdmi interface).

But trying:
gst-launch-1.0 -v v4l2src device=/dev/video0  !
'video/x-raw,framerate=(fraction)50/1,format=RGB' ! videoconvert !
xvimagesink

results in: "could not open display".

The same command works very well when we run it from the GUI by
opening a terminal.

How should we run gstreamer to make it work ?

Thank you,
ranran