title: Video streaming with GStreamer + vaapi
body: <p>I'm trying to do compress webcam image with vaapi***enc and stream the image with UDP protocol.</p>
  
  <p>Are there any good samples or references ?<br>
  All of examples I could find don't try both of vaapi and UDP video streaming at the same time.</p>
  
  <p>On the other hand, I could find out video streaming without using vaapi, like<br>
  Sender : <br>
  <code>gst-launch-1.0 v4l2src device=/dev/video0 ! video/x-raw, width=640, height=480 ! timeoverlay ! tee name="local" ! queue ! autovideosink local. ! queue ! jpegenc! rtpjpegpay ! udpsink host=127.0.0.1 port= 5000</code><br>
  Receiver : <br>
  <code>gst-launch-1.0 udpsrc port=5000 ! application/x-rtp,encoding-name=JPEG,payload=26 ! rtpjpegdepay ! jpegdec ! autovideosink</code></p>
  
  <p>But, I have no idea about how to use vaapijpegenc, or vaapih264enc instead of ***enc which doesn't utilize GPU. <br>
  If I just replaced jpegenc with vaapijpegenc, I get the follows.</p>
  
  <ul>
  <li>ERROR: from element /GstPipeline:pipeline0/GstV4l2Src:v4l2src0: Internal data flow error</li>
  <li>streaming task paused, reason not-negotiated (-4)</li>
  </ul>
  
  <p>How can I solve this problem ? Any samples or references ??<br>
  Thanks in advance.</p>