ffmpeg -f x11grab -s 1920x1080 -i :0.0 -r 60 -c:v libx264rgb -preset ultrafast out.mkv
ffmpeg version 1.2.4 Copyright (c) 2000-2013 the FFmpeg developers
  built on Jan 13 2014 06:42:07 with gcc 4.7.3 (Gentoo 4.7.3-r1 p1.3, pie-0.5.5)
  configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 --mandir=/usr/share/man --enable-shared --cc=x86_64-pc-linux-gnu-gcc --cxx=x86_64-pc-linux-gnu-g++ --ar=x86_64-pc-linux-gnu-ar --optflags='-O2 -pipe -march=amdfam10 -m3dnow -msse -msse2 -mmmx' --extra-cflags='-O2 -pipe -march=amdfam10 -m3dnow -msse -msse2 -mmmx' --extra-cxxflags='-O2 -pipe -march=amdfam10 -m3dnow -msse -msse2 -mmmx' --disable-static --enable-gpl --enable-postproc --enable-avfilter --enable-avresample --disable-stripping --enable-version3 --disable-indev=oss --disable-outdev=oss --enable-bzlib --disable-runtime-cpudetect --disable-debug --disable-doc --disable-gnutls --enable-hardcoded-tables --enable-iconv --enable-network --disable-openssl --enable-ffplay --disable-vaapi --enable-vdpau --enable-zlib --enable-libvo-aacenc --disable-libvo-amrwbenc --enable-libmp3lame --disable-libfdk-aac --disable-libaacplus --disable-libfaac --disable-libtheora --disable-libtwolame --enable-libx264 --enable-libxvid --disable-libcdio --d  libavutil      52. 18.100 / 52. 18.100
  libavcodec     54. 92.100 / 54. 92.100
  libavformat    54. 63.104 / 54. 63.104
  libavdevice    54.  3.103 / 54.  3.103
  libavfilter     3. 42.103 /  3. 42.103
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
[x11grab @ 0x6a6f00] device: :0.0 -> display: :0.0 x: 0 y: 0 width: 1920 height: 1080
[x11grab @ 0x6a6f00] shared memory extension found
[x11grab @ 0x6a6f00] Estimating duration from bitrate, this may be inaccurate
Input #0, x11grab, from ':0.0':
  Duration: N/A, start: 1390323560.579040, bitrate: 1988667 kb/s
    Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1920x1080, 1988667 kb/s, 29.97 tbr, 1000k tbn, 29.97 tbc
File 'out.mkv' already exists. Overwrite ? [y/N] y
using cpu capabilities: MMX2 SSE2Fast LZCNT
[libx264rgb @ 0x6bb790] profile High 4:4:4 Predictive, level 4.2, 4:4:4 8-bit
[libx264rgb @ 0x6bb790] 264 - core 138 - H.264/MPEG-4 AVC codec - Copyleft 2003-2013 - http://www.videolan.org/x264.html - options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=1 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25 scenecut=0 intra_refresh=0 rc=crf mbtree=0 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=0
Output #0, matroska, to 'out.mkv':
  Metadata:
    encoder         : Lavf54.63.104
    Stream #0:0: Video: h264 (H264 / 0x34363248), rgb24, 1920x1080, q=-1--1, 1k tbn, 60 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo -> libx264rgb)
Press [q] to stop, [?] for help
frame=  705 fps= 26 q=13.0 Lsize=    4350kB time=00:00:29.11 bitrate=1223.9kbits/s
video:4345kB audio:0kB subtitle:0 global headers:0kB muxing overhead 0.118583%
[libx264rgb @ 0x6bb790] frame I:3     Avg QP:13.33  size:792766
[libx264rgb @ 0x6bb790] frame P:702   Avg QP:13.20  size:  2949
[libx264rgb @ 0x6bb790] mb I  I16..4: 100.0%  0.0%  0.0%
[libx264rgb @ 0x6bb790] mb P  I16..4:  0.2%  0.0%  0.0%  P16..4:  1.3%  0.0%  0.0%  0.0%  0.0%    skip:98.5%
[libx264rgb @ 0x6bb790] coded y,u,v intra: 17.9% 18.8% 19.2% inter: 0.5% 0.5% 0.5%
[libx264rgb @ 0x6bb790] i16 v,h,dc,p: 59% 39%  0%  1%
[libx264rgb @ 0x6bb790] kb/s:1221.58