[FFmpeg-user] Invalid duration specification for force_key_frames

[Frans Gouverne]

Hello,

since I recompiled ffmpeg some months ago, I cannot use expressions on the
command line anymore, they are simply not recognized. For example:

ffmpeg -re -i demo.mp4 -ac 2 -b:a 64k -ar 44100 -c:v libx264 -r
exp:gt(25,30) -f mp4 output.mp4

Invalid framerate value: exp:gt(25,30)

Below the complete output.

Do I need a specific configuration option when compiling ffmpeg to enable
expressions?

Regards Frans

======================================

ffmpeg version N-49044-g89afa63 Copyright (c) 2000-2013 the FFmpeg
developers
  built on Jan 19 2013 20:36:06 with gcc 4.7.2 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads
--enable-avisynth --enable-bzlib --enable-fontconfi
g --enable-frei0r --enable-gnutls --enable-libass --enable-libbluray
--enable-libcaca --enable-libfreetype --enable-libg
sm --enable-libmp3lame --enable-libopencore-amrnb
--enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --ena
ble-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora
--enable-libtwolame --enable-libvo-aacenc --en
able-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264
--enable-libxavs --enable-libxvid --enable-zlib
--enable-filter=frei0r
  libavutil      52. 15.100 / 52. 15.100
  libavcodec     54. 89.100 / 54. 89.100
  libavformat    54. 61.101 / 54. 61.101
  libavdevice    54.  3.102 / 54.  3.102
  libavfilter     3. 32.101 /  3. 32.101
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'demo.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf54.61.101
  Duration: 00:29:36.00, start: 0.000000, bitrate: 654 kb/s
    Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 /
0x31637661), yuv420p, 480x204 [SAR 1:1 DAR 40:17], 537
kb/s, 24 fps, 24 tbr, 12288 tbn, 48 tbc
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo,
fltp, 111 kb/s
    Metadata:
      handler_name    : SoundHandler
Invalid framerate value: exp:gt(25,30)