Error executing command for rendering preset HTML5 MP4, command #1:
nice -n 19 /usr/bin/ffmpeg -strict experimental -y -i '/var/www/sites/default/files/original/clock_avi4.mp4' -pass 1 -s 176x117 -b 500k -threads 0 -vcodec libx264 -vf "pad:176:144:0:13:000000" -vpre slow_firstpass -an '/var/www/sites/default/files/converted/clock_avi4.mp4' 2>&1
Output:
ffmpeg version 0.7.12, Copyright (c) 2000-2011 the FFmpeg developers
  built on Apr 11 2012 07:40:07 with gcc 4.4.5
  configuration: --enable-libdc1394 --prefix=/usr --extra-cflags='-Wall -g ' --cc='ccache cc' --enable-shared --enable-libmp3lame --enable-gpl --enable-libvorbis --enable-pthreads --enable-libfaac --enable-libxvid --enable-postproc --enable-x11grab --enable-libgsm --enable-libtheora --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libx264 --enable-libspeex --enable-nonfree --disable-stripping --enable-avfilter --enable-libdirac --disable-decoder=libdirac --enable-libfreetype --enable-libschroedinger --disable-encoder=libschroedinger --enable-version3 --enable-libopenjpeg --enable-libvpx --enable-librtmp --extra-libs=-lgcrypt --disable-altivec --disable-armv5te --disable-armv6 --disable-vis
  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
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/var/www/sites/default/files/original/clock_avi4.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf52.31.0
  Duration: 00:00:12.00, start: 0.000000, bitrate: 274 kb/s
    Stream #0.0(und): Video: h264 (Constrained Baseline), yuv420p, 480x320, 216 kb/s, 20 fps, 20 tbr, 20 tbn, 40 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
    Stream #0.1(und): Audio: aac, 44100 Hz, stereo, s16, 53 kb/s
    Metadata:
      creation_time   : 1970-01-01 00:00:00
File for preset 'slow_firstpass' not found