No warning is shown if -vf is specified too often.

[Carl Eugen Hoyos]

The following works as expected:

$ ffmpeg -i fate-suite/lena.pnm -vf hflip out1.png -vf vflip out2.png

The following should show a warning, some users expect that one filter chains' output is used as input for the next filter:

$ ffmpeg -i fate-suite/lena.pnm -vf hflip -vf vflip out.png
ffmpeg version N-68401-g792a500 Copyright (c) 2000-2014 the FFmpeg developers
  built on Dec 13 2014 12:28:49 with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl
  libavutil      54. 15.100 / 54. 15.100
  libavcodec     56. 14.100 / 56. 14.100
  libavformat    56. 15.104 / 56. 15.104
  libavdevice    56.  3.100 / 56.  3.100
  libavfilter     5.  3.101 /  5.  3.101
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
Input #0, image2, from 'fate-suite/lena.pnm':
  Duration: 00:00:00.04, start: 0.000000, bitrate: 39333 kb/s
    Stream #0:0: Video: ppm, rgb24, 256x256, 25 tbr, 25 tbn, 25 tbc
Output #0, image2, to 'out.png':
  Metadata:
    encoder         : Lavf56.15.104
    Stream #0:0: Video: png, rgb24, 256x256, q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc
    Metadata:
      encoder         : Lavc56.14.100 png
Stream mapping:
  Stream #0:0 -> #0:0 (ppm (native) -> png (native))
Press [q] to stop, [?] for help
frame=    1 fps=0.0 q=0.0 Lsize=N/A time=00:00:00.04 bitrate=N/A
video:177kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

[Carl Eugen Hoyos]

Fixed in 301cee61fa61c55b1c178ebfbc590872e8b033e6

[Carl Eugen Hoyos]

Should be really fixed now by Marton Balint in 5d7788f9e86275dac4edd9a38bba0bda565c0dac