testsrc artifacts with specific height values

[Stefano Sabatini]

Summary of the bug:

testsrc generates artifacts in the generated patterns, which appear as a discontinuity in the sliding colored band.
How to reproduce:

ffplay -f lavfi testsrc=s=237x121
ffplay -f lavfi testsrc=s=237x119

This is most likely due to some rounding issue.

[Carl Eugen Hoyos]

$ ffmpeg -f lavfi -i testsrc=s=237x119 -vframes 1 out.png
ffmpeg version N-53670-g1a7ae6b Copyright (c) 2000-2013 the FFmpeg developers
  built on May 30 2013 11:34:27 with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl --disable-indev=jack
  libavutil      52. 34.100 / 52. 34.100
  libavcodec     55. 12.102 / 55. 12.102
  libavformat    55.  8.100 / 55.  8.100
  libavdevice    55.  2.100 / 55.  2.100
  libavfilter     3. 72.100 /  3. 72.100
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  3.100 / 52.  3.100
Input #0, lavfi, from 'testsrc=s=237x119':
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 237x119 [SAR 1:1 DAR 237:119], 25 tbr, 25 tbn, 25 tbc
Output #0, image2, to 'out.png':
  Metadata:
    encoder         : Lavf55.8.100
    Stream #0:0: Video: png, rgb24, 237x119 [SAR 1:1 DAR 237:119], q=2-31, 200 kb/s, 90k tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo -> png)
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:1kB audio:0kB subtitle:0 global headers:0kB muxing overhead -101.554770%

$ ffmpeg -f lavfi -i testsrc=s=237x121 -vframes 1 out.png
ffmpeg version N-53670-g1a7ae6b Copyright (c) 2000-2013 the FFmpeg developers
  built on May 30 2013 11:34:27 with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl --disable-indev=jack
  libavutil      52. 34.100 / 52. 34.100
  libavcodec     55. 12.102 / 55. 12.102
  libavformat    55.  8.100 / 55.  8.100
  libavdevice    55.  2.100 / 55.  2.100
  libavfilter     3. 72.100 /  3. 72.100
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  3.100 / 52.  3.100
Input #0, lavfi, from 'testsrc=s=237x121':
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 237x121 [SAR 1:1 DAR 237:121], 25 tbr, 25 tbn, 25 tbc
Output #0, image2, to 'out.png':
  Metadata:
    encoder         : Lavf55.8.100
    Stream #0:0: Video: png, rgb24, 237x121 [SAR 1:1 DAR 237:121], q=2-31, 200 kb/s, 90k tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo -> png)
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:1kB audio:0kB subtitle:0 global headers:0kB muxing overhead -101.536313%

[Michael Niedermayer]

Fixed in 8a7aabe80b9b2425d0f95c6e6685c5e7aeb5801b