title: How to access compressed stream from webcam with ffmpeg
body: <p>I want to stream webcam live with ffmpeg. My Logitech c920 webcam has an output stream of raw and compressed data. The command <code>ffmpeg -f v4l2 -list_formats all -i /dev/video1</code> produces the following console output:</p>
  
  <pre><code>[video4linux2,v4l2 @ 0x26709e0] Raw       :   yuyv422 :     YUV 4:2:2 (YUYV) : 640x480 160x90 160x120 176x144 320x180 320x240 352x288 432x240 640x360 800x448 800x600 864x480 960x720 1024x576 1280x720 1600x896 1920x1080 2304x1296 2304x1536
  [video4linux2,v4l2 @ 0x26709e0] Compressed:      h264 :                H.264 : 640x480 160x90 160x120 176x144 320x180 320x240 352x288 432x240 640x360 800x448 800x600 864x480 960x720 1024x576 1280x720 1600x896 1920x1080
  [video4linux2,v4l2 @ 0x26709e0] Compressed:     mjpeg :                MJPEG : 640x480 160x90 160x120 176x144 320x180 320x240 352x288 432x240 640x360 800x448 800x600 864x480 960x720 1024x576 1280x720 1600x896 1920x1080
  </code></pre>
  
  <p>I would like to <strong>copy</strong> compressed h264 image and send it to ffserver.</p>
  
  <p>When I use this command <code>ffmpeg -r 25 -f v4l2 -i /dev/video0 -c:v libx264 -b:v 2500k http://localhost:8090/feed1.ffm</code> program gets the <strong>raw</strong> data and transcode it with h264 codec.</p>
  
  <p>When I change the <code>-c:v libx264</code> to <code>-c:v copy</code> I get an error because ffmpeg tries to copy raw camera image.</p>
  
  <p>How can I access h264 compressed image and send it to server?</p>