Green lines with fieldmatch

[Carl Eugen Hoyos]

Some resolutions (?) lead to green bottom lines with fieldmatch.

$ ffmpeg -i test_720x486i_dotcrawl_cut.avi -vf fieldmatch -qscale 2 out.avi
ffmpeg version N-78043-g1d8f9b7 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl
  libavutil      55. 14.100 / 55. 14.100
  libavcodec     57. 22.100 / 57. 22.100
  libavformat    57. 23.100 / 57. 23.100
  libavdevice    57.  0.100 / 57.  0.100
  libavfilter     6. 27.100 /  6. 27.100
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Input #0, avi, from 'test_720x486i_dotcrawl_cut.avi':
  Metadata:
    encoder         : Lavf57.22.100
  Duration: 00:00:01.70, start: 0.000000, bitrate: 11370 kb/s
    Stream #0:0: Video: mpeg4 (Simple Profile) (FMP4 / 0x34504D46), yuv420p, 720x486 [SAR 10:11 DAR 400:297], 11563 kb/s, 29.97 fps, 29.97 tbr, 29.97 tbn, 30k tbc
Please use -q:a or -q:v, -qscale is ambiguous
Output #0, avi, to 'out.avi':
  Metadata:
    ISFT            : Lavf57.23.100
    Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 720x486 [SAR 10:11 DAR 400:297], q=2-31, 200 kb/s, 29.97 fps, 29.97 tbn, 29.97 tbc
    Metadata:
      encoder         : Lavc57.22.100 mpeg4
    Side data:
      unknown side data type 10 (24 bytes)
Stream mapping:
  Stream #0:0 -> #0:0 (mpeg4 (native) -> mpeg4 (native))
Press [q] to stop, [?] for help
frame=   51 fps=0.0 q=2.0 Lsize=    1756kB time=00:00:01.70 bitrate=8452.7kbits/s speed=9.69x 
video:1749kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.391348%

[Clément Bœsch]

Fixed in 6c0318c4ba8e749911324d96e7c04fcc04661c97