ffmpeg -i source.flv -vcodec libx264 -crf 26 -preset veryfast -bf 0 -acodec copy -scodec copy -threads 0 test2.flv
ffmpeg version 0.9.1, Copyright (c) 2000-2012 the FFmpeg developers
  built on Jan 28 2012 17:45:19 with gcc 4.6.2
  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='-march=corei7-avx -O2 -pipe -fomit-frame-pointer' --extra-cflags='-march=corei7-avx -O2 -pipe -fomit-frame-pointer' --extra-cxxflags='-march=corei7-avx -O2 -pipe -fomit-frame-pointer' --disable-static --enable-gpl --enable-version3 --enable-postproc --enable-avfilter --disable-stripping --disable-debug --disable-doc --enable-runtime-cpudetect --enable-openssl --enable-nonfree --enable-avconv --enable-libmp3lame --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-libaacplus --enable-nonfree --enable-libfaac --enable-nonfree --enable-libcdio --enable-libdc1394 --enable-openal --disable-indev=v4l --disable-indev=jack --enable-libv4l2 --enable-frei0r --enable-libfreetype --enable-pthreads --enable-libopencore-amrwb --enable-libope  libavutil    51. 32. 0 / 51. 32. 0
  libavcodec   53. 42. 4 / 53. 42. 4
  libavformat  53. 24. 2 / 53. 24. 2
  libavdevice  53.  4. 0 / 53.  4. 0
  libavfilter   2. 53. 0 /  2. 53. 0
  libswscale    2.  1. 0 /  2.  1. 0
  libpostproc  51.  2. 0 / 51.  2. 0
Input #0, flv, from 'source.flv':
  Duration: 00:40:48.70, start: 0.000000, bitrate: 307 kb/s
    Stream #0:0: Video: flv1, yuv420p, 312x240, 1k tbr, 1k tbn, 1k tbc
    Stream #0:1: Audio: nellymoser, 8000 Hz, mono, s16
[buffer @ 0xa40e40] w:312 h:240 pixfmt:yuv420p tb:1/1000000 sar:0/1 sws_param:
[libx264 @ 0x9c8460] using cpu capabilities: MMX2 SSE2Fast SSSE3 FastShuffle SSE4.2 AVX
[libx264 @ 0x9c8460] profile High, level 4.2
[libx264 @ 0x9c8460] 264 - core 120 - H.264/MPEG-4 AVC codec - Copyleft 2003-2011 - 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=6 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=1 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=10 rc=crf mbtree=1 crf=26.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, flv, to 'test2.flv':
  Metadata:
    encoder         : Lavf53.24.2
    Stream #0:0: Video: h264 ([7][0][0][0] / 0x0007), yuv420p, 312x240, q=-1--1, 1k tbn, 1k tbc
    Stream #0:1: Audio: nellymoser ([6][0][0][0] / 0x0006), 8000 Hz, mono
Stream mapping:
  Stream #0:0 -> #0:0 (flv -> libx264)
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame=19488 fps=691 q=-1.0 Lsize=   37746kB time=00:40:48.31 bitrate= 126.3kbits/s
video:30454kB audio:5735kB global headers:0kB muxing overhead 4.303332%
[libx264 @ 0x9c8460] frame I:112   Avg QP:20.47  size:  4606
[libx264 @ 0x9c8460] frame P:19376 Avg QP:23.80  size:  1583
[libx264 @ 0x9c8460] mb I  I16..4:  3.4% 66.1% 30.6%
[libx264 @ 0x9c8460] mb P  I16..4:  0.4%  8.0%  0.2%  P16..4: 30.4% 19.8% 11.5%  0.0%  0.0%    skip:29.6%
[libx264 @ 0x9c8460] 8x8 transform intra:90.9% inter:43.3%
[libx264 @ 0x9c8460] coded y,uvDC,uvAC intra: 67.5% 62.5% 4.9% inter: 23.3% 15.3% 0.3%
[libx264 @ 0x9c8460] i16 v,h,dc,p: 31% 41% 23%  5%
[libx264 @ 0x9c8460] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 25% 26% 42%  2%  1%  1%  1%  1%  2%
[libx264 @ 0x9c8460] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 31% 19% 16%  6%  5%  7%  4%  8%  5%
[libx264 @ 0x9c8460] i8c dc,h,v,p: 57% 19% 21%  3%
[libx264 @ 0x9c8460] Weighted P-Frames: Y:0.6% UV:0.3%
[libx264 @ 0x9c8460] kb/s:101.88