$ avconv -f x11grab -s 1008x1072 -r 24 -i :0.0+8,70 -c:v ffvhuff -threads 0 /tmp/out.avi
avconv version 0.8.4-6:0.8.4-1, Copyright (c) 2000-2012 the Libav developers
  built on Oct 22 2012 21:36:00 with gcc 4.7.2
[x11grab @ 0xfd34e0] device: :0.0+8,70 -> display: :0.0 x: 8 y: 70 width: 1008 height: 1072
[x11grab @ 0xfd34e0] shared memory extension  found
[x11grab @ 0xfd34e0] Estimating duration from bitrate, this may be inaccurate
Input #0, x11grab, from ':0.0+8,70':
  Duration: N/A, start: 1352669412.075731, bitrate: 829882 kb/s
    Stream #0.0: Video: rawvideo, bgra, 1008x1072, 829882 kb/s, 24 tbr, 1000k tbn, 24 tbc
File '/tmp/out.avi' already exists. Overwrite ? [y/N] y
[buffer @ 0xfe5540] w:1008 h:1072 pixfmt:bgra
Output #0, avi, to '/tmp/out.avi':
  Metadata:
    ISFT            : Lavf53.21.0
    Stream #0.0: Video: ffvhuff, bgra, 1008x1072, q=2-31, 200 kb/s, 24 tbn, 24 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo -> ffvhuff)
Press ctrl-c to stop encoding
^Cframe=   14 fps=  0 q=0.0 Lsize=   17685kB time=2.54 bitrate=56998.8kbits/s    
video:17678kB audio:0kB global headers:0kB muxing overhead 0.039466%
Received signal 2: terminating.