FFMPEG命令问题

Question

我和FFMPEG有个问题。确切地说，我正试图从视频文件中生成一些“有意义的”缩略图。我在网上找到了这个命令：

ffmpeg -ss 3 -i input.mp4 -vf "select=gt(scene\,0.4)" -frames:v 5 -vsync vfr fps=fps=1/600 out%02d.jpg

遗憾的是，这对我不起作用，因为我得到了：

[NULL @ 0x86c2420] Unable to find a suitable output format for 'fps=fps=1/600'
fps=fps=1/600: Invalid argument

我尝试过将"fps=fps=1/600"包含在-vf中，结果只生成了一张图片。我做错了什么？

编辑：

这是一个完整输出的例子：

$ ffmpeg -ss 3 -i video.ogg -vf "select=gt(scene\,0.4)" -frames:v 5 -vsync vfr fps=fps=1/600 out%02d.jpg
ffmpeg version 2.5.3 Copyright (c) 2000-2015 the FFmpeg developers
  built on Jan 10 2015 23:26:13 with gcc 4.9.2 (GCC) 20141224 (prerelease)
  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-avisynth --enable-avresample --enable-fontconfig --enable-gnutls --enable-gpl --enable-libass --enable-libbluray --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libv4l2 --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-runtime-cpudetect --enable-shared --enable-swresample --enable-vdpau --enable-version3 --enable-x11grab
  libavutil      54. 15.100 / 54. 15.100
  libavcodec     56. 13.100 / 56. 13.100
  libavformat    56. 15.102 / 56. 15.102
  libavdevice    56.  3.100 / 56.  3.100
  libavfilter     5.  2.103 /  5.  2.103
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
[theora @ 0x9b59140] 7 bits left in packet 82
[ogg @ 0x9b586e0] Broken file, keyframe not correctly marked.
    Last message repeated 2 times
Input #0, ogg, from 'video.ogg':
  Duration: 00:09:56.46, start: 0.000000, bitrate: 2237 kb/s
    Stream #0:0: Video: theora, yuv420p, 854x480, 24 tbr, 24 tbn, 24 tbc
    Stream #0:1: Audio: vorbis, 48000 Hz, stereo, fltp, 192 kb/s
[NULL @ 0x9b97660] Unable to find a suitable output format for 'fps=fps=1/600'
fps=fps=1/600: Invalid argument

Answer 1

我所要做的就是在"fps=fps=1/600"之前添加-vf