./ffmpeg -f x11grab -video_size 1366x664 -framerate 30 -i $DISPLAY.0  -aspect 1366:664 -pix_fmt yuv420p -vcodec libx264 output.mkv
ffmpeg version git-2016-08-28-a37e6dd Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  configuration: --prefix=/home/user/ffmpeg_build --pkg-config-flags=--static --extra-cflags=-I/home/user/ffmpeg_build/include --extra-ldflags=-L/home/rabeet/ffmpeg_build/lib --bindir=/home/rabeet/bin --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libx264 --enable-nonfree --enable-opengl
  libavutil      55. 29.100 / 55. 29.100
  libavcodec     57. 54.101 / 57. 54.101
  libavformat    57. 48.101 / 57. 48.101
  libavdevice    57.  0.102 / 57.  0.102
  libavfilter     6. 57.100 /  6. 57.100
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  1.100 /  2.  1.100
  libpostproc    54.  0.100 / 54.  0.100
[x11grab @ 0x24e8540] Stream #0: not enough frames to estimate rate; consider increasing probesize
Input #0, x11grab, from ':0.0':
  Duration: N/A, start: 1472720205.671475, bitrate: N/A
    Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1366x664, 30 fps, 1000k tbr, 1000k tbn, 1000k tbc
File 'output.mkv' already exists. Overwrite ? [y/N] y
[libx264 @ 0x24f2440] using SAR=1/1
[libx264 @ 0x24f2440] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX LZCNT
[libx264 @ 0x24f2440] profile High, level 3.2
[libx264 @ 0x24f2440] 264 - core 142 r2389 956c8d8 - H.264/MPEG-4 AVC codec - Copyleft 2003-2014 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=3 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
[matroska @ 0x24f0a60] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
Output #0, matroska, to 'output.mkv':
  Metadata:
    encoder         : Lavf57.48.101
    Stream #0:0: Video: h264 (libx264) (H264 / 0x34363248), yuv420p, 1366x664 [SAR 23904:23905 DAR 72:35], q=-1--1, 30 fps, 1k tbn, 30 tbc
    Metadata:
      encoder         : Lavc57.54.101 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[swscaler @ 0x24fe220] Warning: data is not aligned! This can lead to a speedloss
Past duration 0.734077 too large
Past duration 0.911125 too large
frame=   19 fps=0.0 q=0.0 size=       0kB time=00:00:00.00 bitrate=N/A dup=0 droPast duration 0.695259 too large
Past duration 0.606010 too large
Past duration 0.999519 too large
Past duration 0.801674 too large
Past duration 0.935539 too large
Past duration 0.892052 too large
Past duration 0.904518 too large
Past duration 0.789162 too large
frame=   35 fps= 33 q=0.0 size=       0kB time=00:00:00.00 bitrate=N/A dup=0 droPast duration 0.871544 too large
Past duration 0.949806 too large
Past duration 0.956718 too large
Past duration 0.987968 too large
frame=   51 fps= 32 q=29.0 size=       2kB time=00:00:00.03 bitrate= 416.5kbits/Past duration 0.956871 too large
Past duration 0.970589 too large
frame=   66 fps= 32 q=29.0 size=       2kB time=00:00:01.76 bitrate=  11.4kbits/Past duration 0.955269 too large
Past duration 0.971016 too large
frame=   82 fps= 32 q=29.0 size=       3kB time=00:00:02.30 bitrate=  12.0kbits/Past duration 0.946617 too large
Past duration 0.875252 too large
Past duration 0.998802 too large
frame=   98 fps= 31 q=29.0 size=       4kB time=00:00:02.83 bitrate=  11.9kbits/Past duration 0.918571 too large
frame=  113 fps= 31 q=29.0 size=       5kB time=00:00:03.33 bitrate=  12.4kbits/Past duration 0.963066 too large
Past duration 0.991219 too large
frame=  129 fps= 31 q=29.0 size=       6kB time=00:00:03.86 bitrate=  13.4kbits/Past duration 0.979576 too large
^Cav_interleaved_write_frame(): Immediate exit requested
Error writing trailer of output.mkv: Immediate exit requestedframe=  139 fps= 29 q=29.0 Lsize=      10kB time=00:00:05.36 bitrate=  14.8kbits/s dup=0 drop=36 speed=1.13x
video:8kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 17.149616%
[libx264 @ 0x24f2440] frame I:1     Avg QP: 6.00  size:   216
[libx264 @ 0x24f2440] frame P:40    Avg QP:14.93  size:    73
[libx264 @ 0x24f2440] frame B:98    Avg QP:15.28  size:    53
[libx264 @ 0x24f2440] consecutive B-frames:  5.8%  0.0%  2.2% 92.1%
[libx264 @ 0x24f2440] mb I  I16..4: 100.0%  0.0%  0.0%
[libx264 @ 0x24f2440] mb P  I16..4:  0.0%  0.0%  0.0%  P16..4:  0.1%  0.0%  0.0%  0.0%  0.0%    skip:99.9%
[libx264 @ 0x24f2440] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  0.1%  0.0%  0.0%  direct: 0.0%  skip:99.9%  L0:60.7% L1:39.0% BI: 0.2%
[libx264 @ 0x24f2440] 8x8 transform intra:0.8% inter:0.0%
[libx264 @ 0x24f2440] coded y,uvDC,uvAC intra: 0.9% 0.0% 0.0% inter: 0.0% 0.0% 0.0%
[libx264 @ 0x24f2440] i16 v,h,dc,p: 98%  0%  2%  0%
[libx264 @ 0x24f2440] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu:  0% 25% 75%  0%  0%  0%  0%  0%  0%
[libx264 @ 0x24f2440] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 33% 11% 46%  1%  3%  2%  1%  2%  1%
[libx264 @ 0x24f2440] i8c dc,h,v,p: 100%  0%  0%  0%
[libx264 @ 0x24f2440] Weighted P-Frames: Y:2.5% UV:0.0%
[libx264 @ 0x24f2440] ref P L0: 93.6%  0.0%  4.5%  1.9%
[libx264 @ 0x24f2440] ref B L0: 67.3% 29.9%  2.9%
[libx264 @ 0x24f2440] kb/s:11.44
Exiting normally, received signal 2.