Video streaming README: Add instructions to generate test stream

src/VideoStreaming/README.md

@@ -17,6 +17,11 @@ gst-launch-1.0 uvch264src initial-bitrate=1000000 average-bitrate=1000000 iframe
 
 Where xxx.xxx.xxx.xxx is the IP address where QGC is running. You may tweak the bitrate, the resolution and the FPS based on your needs and/or available bandwidth.
 
+To test using a test source on localhost, you can run this command:
+```
+gst-launch-1.0 videotestsrc pattern=ball ! x264enc ! rtph264pay ! udpsink host=127.0.0.1 port=5000
+```
+
 On the receiving end, if you want to test it from the command line, you can use something like:
 ```
 gst-launch-1.0 udpsrc port=5000 caps='application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264' ! rtph264depay ! avdec_h264 ! autovideosink fps-update-interval=1000 sync=false