ffmpeg version 0.7.8, Copyright (c) 2000-2011 the FFmpeg developers
  built on Jan  8 2012 19:12:42 with gcc 4.5.3
  configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 --mandir=/usr/share/man --enable-shared --cc=x86_64-pc-linux-gnu-gcc --disable-static --enable-gpl --enable-version3 --enable-postproc --enable-avfilter --disable-stripping --disable-debug --disable-doc --disable-network --disable-vaapi --disable-vdpau --enable-libmp3lame --enable-libvo-aacenc --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --disable-indev=v4l --disable-indev=oss --disable-indev=jack --enable-x11grab --disable-outdev=oss --enable-libfreetype --enable-libspeex --disable-altivec --disable-avx --cpu=k8 --enable-hardcoded-tables
  libavutil    50. 43. 0 / 50. 43. 0
  libavcodec   52.123. 0 / 52.123. 0
  libavformat  52.111. 0 / 52.111. 0
  libavdevice  52.  5. 0 / 52.  5. 0
  libavfilter   1. 80. 0 /  1. 80. 0
  libswscale    0. 14. 1 /  0. 14. 1
  libpostproc  51.  2. 0 / 51.  2. 0
[flv @ 0x624e90] Estimating duration from bitrate, this may be inaccurate

Seems stream 0 codec frame rate differs from container frame rate: 50.00 (50/1) -> 25.00 (50/2)
Input #0, flv, from 'in.flv':
  Duration: 01:12:28.24, start: 0.000000, bitrate: N/A
    Stream #0.0: Video: h264 (Main), yuv420p, 1280x720 [PAR 1:1 DAR 16:9], 25 tbr, 1k tbn, 50 tbc
File 'xxx.flv' already exists. Overwrite ? [y/N] y
Output #0, flv, to 'xxx.flv':
  Metadata:
    encoder         : Lavf52.111.0
    Stream #0.0: Video: libx264, yuv420p, 1280x720 [PAR 1:1 DAR 16:9], q=2-31, 1k tbn, 25 tbc