This commands sends a previously captured screencap (X11grab=>avi) to yuoutube

(i /dev/fd/63 is a pipe to /dev/zero to generate a silenced audio stream)

ffmpeg -i screen_0.avi -ar 44100 -acodec pcm_s16le -f s16le -ac 2 -i /dev/fd/63 -vcodec libx264 -preset veryfast -maxrate 3000k -bufsize 6000k -pix_fmt yuv420p -g 50 -acodec libmp3lame -b:a 128k -ac 2 -ar 44100 -f flv rtmp://x.rtmp.youtube.com/live2/wrl.delvaux.q324-jza0-vk07-2cb6
ffmpeg version 0.10.11-7:0.10.11-1~saucy1 Copyright (c) 2000-2014 the FFmpeg developers
  built on Feb  6 2014 16:55:15 with gcc 4.8.1
  configuration: --arch=amd64 --disable-stripping --enable-pthreads --enable-runtime-cpudetect --extra-version='7:0.10.11-1~saucy1' --libdir=/usr/lib/x86_64-linux-gnu --prefix=/usr --enable-bzlib --enable-libdc1394 --enable-libfreetype --enable-frei0r --enable-gnutls --enable-libgsm --enable-libmp3lame --enable-librtmp --enable-libopencv --enable-libopenjpeg --enable-libpulse --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-vaapi --enable-vdpau --enable-libvorbis --enable-libvpx --enable-zlib --enable-gpl --enable-postproc --enable-libcdio --enable-x11grab --enable-libx264 --shlibdir=/usr/lib/x86_64-linux-gnu --enable-shared --disable-static
  avcodec     configuration: --arch=amd64 --disable-stripping --enable-pthreads --enable-runtime-cpudetect --extra-version='7:0.10.11-1~saucy1' --libdir=/usr/lib/x86_64-linux-gnu --prefix=/usr --enable-bzlib --enable-libdc1394 --enable-libfreetype --enable-frei0r --enable-gnutls --enable-libgsm --enable-libmp3lame --enable-librtmp --enable-libopencv --enable-libopenjpeg --enable-libpulse --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-vaapi --enable-vdpau --enable-libvorbis --enable-libvpx --enable-zlib --enable-gpl --enable-postproc --enable-libcdio --enable-x11grab --enable-libx264 --shlibdir=/usr/lib/x86_64-linux-gnu --enable-shared --disable-static --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libvo-aacenc --enable-libvo-amrwbenc
  libavutil      51. 35.100 / 51. 35.100
  libavcodec     53. 61.100 / 53. 61.100
  libavformat    53. 32.100 / 53. 32.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 61.100 /  2. 61.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  6.100 /  0.  6.100
  libpostproc    52.  0.100 / 52.  0.100
[avi @ 0x1d47840] max_analyze_duration 5000000 reached at 5000000
Input #0, avi, from 'screen_0.avi':
  Metadata:
    encoder         : Lavf53.32.100
  Duration: 00:09:48.40, start: 0.000000, bitrate: 371 kb/s
    Stream #0:0: Video: h264 (High) (H264 / 0x34363248), yuv420p, 1920x1080, 30 fps, 30 tbr, 30 tbn, 60 tbc
[s16le @ 0x1d3aa40] Estimating duration from bitrate, this may be inaccurate
Input #1, s16le, from '/dev/fd/63':
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #1:0: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
[buffer @ 0x1e47f00] w:1920 h:1080 pixfmt:yuv420p tb:1/1000000 sar:0/1 sws_param:
[libx264 @ 0x1d32ae0] using cpu capabilities: MMX2 SSE2Fast SSSE3 FastShuffle SSE4.2 AVX
[libx264 @ 0x1d32ae0] profile High, level 4.0
[libx264 @ 0x1d32ae0] 264 - core 123 r2189 35cf912 - H.264/MPEG-4 AVC codec - Copyleft 2003-2012 - http://www.videolan.org/x264.html - options: cabac=1 ref=1 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=2 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=12 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=1 keyint=50 keyint_min=5 scenecut=40 intra_refresh=0 rc_lookahead=10 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 vbv_maxrate=3000 vbv_bufsize=6000 crf_max=0.0 nal_hrd=none ip_ratio=1.40 aq=1:1.00
Output #0, flv, to 'rtmp://x.rtmp.youtube.com/live2/wrl.delvaux.q324-jza0-vk07-2cb6':
  Metadata:
    encoder         : Lavf53.32.100
    Stream #0:0: Video: h264 ([7][0][0][0] / 0x0007), yuv420p, 1920x1080, q=-1--1, 1k tbn, 30 tbc
    Stream #0:1: Audio: mp3 ([2][0][0][0] / 0x0002), 44100 Hz, 2 channels, s16, 128 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (h264 -> libx264)
  Stream #1:0 -> #0:1 (pcm_s16le -> libmp3lame)
Press [q] to stop, [?] for help
172+0 records in159 q=29.0 size=   10788kB time=00:02:51.07 bitrate= 516.6kbits/s
171+0 records out
30164400 bytes (30 MB) copied, 33.1506 s, 910 kB/s
frame= 5177 fps=159 q=-1.0 Lsize=   10872kB time=00:02:51.46 bitrate= 519.4kbits/s
video:7989kB audio:2679kB global headers:0kB muxing overhead 1.912761%
[libx264 @ 0x1d32ae0] frame I:104   Avg QP:20.10  size: 63279
[libx264 @ 0x1d32ae0] frame P:1377  Avg QP:27.00  size:   928
[libx264 @ 0x1d32ae0] frame B:3696  Avg QP:28.76  size:    87
[libx264 @ 0x1d32ae0] consecutive B-frames:  4.6%  0.3%  0.6% 94.4%
[libx264 @ 0x1d32ae0] mb I  I16..4: 85.9%  1.0% 13.1%
[libx264 @ 0x1d32ae0] mb P  I16..4:  0.7%  0.0%  0.1%  P16..4:  0.5%  0.0%  0.0%  0.0%  0.0%    skip:98.7%
[libx264 @ 0x1d32ae0] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  0.0%  0.0%  0.0%  direct: 0.0%  skip:99.9%  L0:52.2% L1:46.6% BI: 1.2%
[libx264 @ 0x1d32ae0] 8x8 transform intra:1.4% inter:7.8%
[libx264 @ 0x1d32ae0] coded y,uvDC,uvAC intra: 10.8% 4.5% 3.4% inter: 0.1% 0.0% 0.0%
[libx264 @ 0x1d32ae0] i16 v,h,dc,p: 75% 25%  0%  0%
[libx264 @ 0x1d32ae0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 16% 49% 26%  1%  1%  1%  1%  1%  4%
[libx264 @ 0x1d32ae0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 30% 32% 19%  2%  3%  3%  3%  3%  4%
[libx264 @ 0x1d32ae0] i8c dc,h,v,p: 86% 12%  2%  0%
[libx264 @ 0x1d32ae0] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x1d32ae0] kb/s:379.20
Received signal 2: terminating.