报错如下：
root@syl:modetest# gst-launch-1.0 --gst-plugin-path=/usr/lib/aarch64-linux-gnu/gstreamer-1.0 rtspsrc location=rtsp://admin:1234abcd@172.168.1.238:554/Streaming/Channels/201 latency=0 ! rtph264depay ! capsfilter caps="video/x-h264" ! h264parse ! mppvideodec ! videoconvert ! videoscale ! video/x-raw,width=800,height=600 ! rkximagesink
librga:RGA_GET_VERSION:3.02,3.020000
ctx=0x55becce810,ctx->rgaFd=3
Rga built version:version:+2017-09-28 10:12:42
Setting pipeline to PAUSED ...
ERROR: from element /GstPipeline:pipeline0/GstRkXImageSink:rkximagesink0: Could not initialise X output
Additional debug info:
ximagesink.c(1648): gst_x_image_sink_xcontext_get (): /GstPipeline:pipeline0/GstRkXImageSink:rkximagesink0:
Could not open display
ERROR: pipeline doesn't want to preroll.
Failed to set pipeline to PAUSED.
Setting pipeline to NULL ...
Freeing pipeline ...