问FFMPEG视频编码错误

EN

---:/media/New Volume/temp$ ffmpeg -f image2 -i image%1d.png -vcodec libx264 \
-preset ultrafast -crf 15 output.mp4
ffmpeg version git-2012-03-24-2571506 Copyright (c) 2000-2012 the FFmpeg developers
  built on Mar 24 2012 03:47:02 with gcc 4.6.1
  configuration: --enable-gpl --enable-libfaac --enable-libmp3lame \
    --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora \
    --enable-libvorbis --enable-libx264 --enable-nonfree --enable-version3 \
    --enable-x11grab
  libavutil      51. 44.100 / 51. 44.100
  libavcodec     54. 12.100 / 54. 12.100
  libavformat    54.  2.100 / 54.  2.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 65.102 /  2. 65.102
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  7.100 /  0.  7.100
  libpostproc    52.  0.100 / 52.  0.100
// ERORRS:: 
[png @ 0xa4d5120] Missing png signature
[image2 @ 0xa4ceb00] decoding for stream 0 failed
[image2 @ 0xa4ceb00] Could not find codec parameters (Video: png)
image%1d.png: could not find codec parameters