[me@mbp ~]$ ffmpeg -i ~/Desktop/iShowU-Capture.mov -s 840x525 -vcodec mpeg4 -an ~/Desktop/out.mp4
FFmpeg version UNKNOWN, Copyright (c) 2000-2010 the FFmpeg developers
  built on Jul 22 2010 20:05:30 with gcc 4.2.1 (Apple Inc. build 5646)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/HEAD --disable-debug --enable-shared --enable-pthreads --enable-nonfree --enable-gpl --enable-libx264 --enable-libfaac --enable-libfaad --enable-libmp3lame
  libavutil     50.14. 0 / 50.14. 0
  libavcodec    52.66. 0 / 52.66. 0
  libavformat   52.61. 0 / 52.61. 0
  libavdevice   52. 2. 0 / 52. 2. 0
  libswscale     0.10. 0 /  0.10. 0
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x10100b000]MAX_READ_SIZE:5000000 reached
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/Users/me/Desktop/iShowU-Capture.mov':
  Metadata:
    major_brand     : qt
    minor_version   : 537199360
    compatible_brands: qt
  Duration: 00:00:03.09, start: 0.000000, bitrate: 42988 kb/s
    Stream #0.0(eng): Video: Apple Intermediate Codec, 1680x1050, 42984 kb/s, 14.85 fps, 1500 tbr, 1500 tbn, 1500 tbc
swScaler: Unknown format is not supported as input pixel format
Cannot get resampling context