$ ffserver -d -f /etc/ffserver.conf & ffmpeg -v verbose -r 30 -s 320x240 -f video4linux2 -i /dev/video0 http://localhost:8080/webcam.ffm
[2] 2232
ffserver version 1.0 Copyright (c) 2000-2012 the FFmpeg developers
ffmpeg version 1.0 Copyright (c) 2000-2012 the FFmpeg developers
  built on Oct  3 2012 09:24:54 with gcc 4.6 (Debian 4.6.3-8+rpi1)
  configuration:
  libavutil      51. 73.101 / 51. 73.101
  libavcodec     54. 59.100 / 54. 59.100
  libavformat    54. 29.104 / 54. 29.104
  libavdevice    54.  2.101 / 54.  2.101
  built on Oct  3 2012 09:24:54 with gcc 4.6 (Debian 4.6.3-8+rpi1)
  configuration:
  libavutil      51. 73.101 / 51. 73.101
  libavcodec     54. 59.100 / 54. 59.100
  libavfilter     3. 17.100 /  3. 17.100
  libswscale      2.  1.101 /  2.  1.101
  libswresample   0. 15.100 /  0. 15.100
  libavformat    54. 29.104 / 54. 29.104
  libavdevice    54.  2.101 / 54.  2.101
  libavfilter     3. 17.100 /  3. 17.100
  libswscale      2.  1.101 /  2.  1.101
  libswresample   0. 15.100 /  0. 15.100
[video4linux2,v4l2 @ 0x2a1f620] [3]Capabilities: 4000001
bind(port 8080): Address already in use
Sat Oct 27 23:37:44 2012 Could not start server
[video4linux2,v4l2 @ 0x2a1f620] Estimating duration from bitrate, this may be inaccurate
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 939.346718, bitrate: 36864 kb/s
    Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 320x240, 36864 kb/s, 30 tbr, 1000k tbn, 30 tbc
Sat Oct 27 23:37:48 2012 127.0.0.1 - - New connection: GET /webcam.ffm
Sat Oct 27 23:37:48 2012 127.0.0.1 - - [GET] "/webcam.ffm HTTP/1.1" 200 16463
Sat Oct 27 23:37:48 2012 127.0.0.1 - - New connection: POST /webcam.ffm
[graph 0 input from stream 0:0 @ 0x2a21b40] w:320 h:240 pixfmt:yuyv422 tb:1/30 fr:30/1 sar:0/1 sws_param:flags=2
[graph 0 input from stream 0:0 @ 0x2a21b40] TB:0.033333 FRAME_RATE:30.000000 SAMPLE_RATE:nan
[scaler for output stream 0:0 @ 0x2a25120] w:320 h:240 fmt:yuyv422 sar:0/1 -> w:320 h:240 fmt:yuvj422p sar:0/1 flags:0x4
Output #0, ffm, to 'http://localhost:8080/webcam.ffm':
  Metadata:
    encoder         : Lavf54.29.104
    Stream #0:0: Video: mjpeg, yuvj422p, 320x240, q=1-10, 3200 kb/s, 1000k tbn, 30 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo -> mjpeg)
Press [q] to stop, [?] for help
Sat Oct 27 23:38:01 2012 192.168.0.6 - - New connection: GET /webcam.mjpegbits/s
The v4l2 frame is 367 bytes, but 153600 bytes are expected bitrate=3214.0kbits/s
/dev/video0: Invalid data found when processing input
No more output streams to write to, finishing.
frame=  647 fps= 14 q=4.4 Lsize=    8464kB time=00:00:21.56 bitrate=3215.0kbits/s
video:8421kB audio:0kB subtitle:0 global headers:0kB muxing overhead 0.511829%
[2]+  Exit 1                  ffserver -d -f /etc/ffserver.conf