Save
gst-launch-1.0 v4l2src io-mode=0 device=/dev/video0 do-timestamp=true ! nvvideoconvert ! 'video/x-raw(memory:NVMM)' ! nvv4l2h265enc bitrate=4000000 ! h265parse ! matroskamux ! filesink location=test.mkv

Preview
gst-launch-1.0 v4l2src io-mode=0 device=/dev/video0 do-timestamp=true ! 'video/x-raw, width=1920, height=1080, framerate=30/1, format=UYVY' ! xvimagesink sync=false

Preview & save
gst-launch-1.0 v4l2src io-mode=0 device=/dev/video0 do-timestamp=true ! 'video/x-raw, width=1920, height=1080, framerate=30/1, format=UYVY' ! videoconvert ! tee name=t ! queue ! 'video/x-raw, format=(string)UYVY' ! nvvideoconvert ! 'video/x-raw(memory:NVMM)' ! nvv4l2h265enc bitrate=4000000 ! h265parse ! matroskamux ! filesink location=test.mkv sync=false t. ! queue ! xvimagesink