[FFmpeg-user] Why does this half the filesize

[Cecil Westerhof]

When executing:
    ffmpeg -y -sameq -i original/resolutie.avi resolutie.avi

The resulting file is half as big as the original one. Why is this?

The reason I do this, is that I capture something from XWindows and I
have to cut the last few seconds.

If it is useful:
ffmpeg -i original/resolutie.avi 
FFmpeg version SVN-r201104161305, Copyright (c) 2000-2011 the FFmpeg developers
  built on Apr 16 2011 11:36:21 with gcc 4.5.1 20101208 [gcc-4_5-branch revision 167585]
  configuration: --shlibdir=/usr/lib --prefix=/usr --mandir=/usr/share/man --libdir=/usr/lib --enable-shared --enable-libmp3lame --enable-libvorbis --enable-libtheora --enable-libspeex --enable-libxvid --enable-postproc --enable-gpl --enable-x11grab --extra-cflags='-fomit-frame-pointer -fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gsm' --enable-debug --disable-stripping --enable-libgsm --enable-libschroedinger --enable-libdirac --enable-avfilter --enable-libvpx --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libx264 --enable-libdc1394 --enable-pthreads --enable-librtmp
  libavutil    50. 40. 1 / 50. 40. 1
  libavcodec   52.119. 1 / 52.119. 1
  libavformat  52.108. 0 / 52.108. 0
  libavdevice  52.  4. 0 / 52.  4. 0
  libavfilter   1. 79. 0 /  1. 79. 0
  libswscale    0. 13. 0 /  0. 13. 0
  libpostproc  51.  2. 0 / 51.  2. 0
Input #0, avi, from 'original/resolutie.avi':
  Metadata:
    encoder         : Lavf52.108.0
  Duration: 00:00:53.93, start: 0.000000, bitrate: 2809 kb/s
    Stream #0.0: Video: mpeg4, yuv420p, 1028x795 [PAR 1:1 DAR 1028:795], 15 tbr, 15 tbn, 15 tbc
    Stream #0.1: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
At least one output file must be specified



ffmpeg -i resolutie.avi 
FFmpeg version SVN-r201104161305, Copyright (c) 2000-2011 the FFmpeg developers
  built on Apr 16 2011 11:36:21 with gcc 4.5.1 20101208 [gcc-4_5-branch revision 167585]
  configuration: --shlibdir=/usr/lib --prefix=/usr --mandir=/usr/share/man --libdir=/usr/lib --enable-shared --enable-libmp3lame --enable-libvorbis --enable-libtheora --enable-libspeex --enable-libxvid --enable-postproc --enable-gpl --enable-x11grab --extra-cflags='-fomit-frame-pointer -fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gsm' --enable-debug --disable-stripping --enable-libgsm --enable-libschroedinger --enable-libdirac --enable-avfilter --enable-libvpx --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libx264 --enable-libdc1394 --enable-pthreads --enable-librtmp
  libavutil    50. 40. 1 / 50. 40. 1
  libavcodec   52.119. 1 / 52.119. 1
  libavformat  52.108. 0 / 52.108. 0
  libavdevice  52.  4. 0 / 52.  4. 0
  libavfilter   1. 79. 0 /  1. 79. 0
  libswscale    0. 13. 0 /  0. 13. 0
  libpostproc  51.  2. 0 / 51.  2. 0
Input #0, avi, from 'resolutie.avi':
  Metadata:
    encoder         : Lavf52.108.0
  Duration: 00:00:53.93, start: 0.000000, bitrate: 1458 kb/s
    Stream #0.0: Video: mpeg4, yuv420p, 1028x795 [PAR 1:1 DAR 1028:795], 15 tbr, 15 tbn, 15 tbc
    Stream #0.1: Audio: mp2, 44100 Hz, stereo, s16, 64 kb/s
At least one output file must be specified

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof