系统已经配置好摄像头，测试命令如下
export DISPLAY=:0
export XAUTHORITY=/home/youyeetoo/.Xauthority
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/lib/aarch64-linux-gnu/gstreamer-1.0
WIDTH=1920
HEIGHT=1080
SINK=xvimagesink
gst-launch-1.0 v4l2src device=/dev/video0 ! \
video/x-raw,format=NV12,width=${WIDTH},height=${HEIGHT}, framerate=30/1 ! videoconvert ! $SINK