ffmpeg- usando ffmpeg para tirar a tela de cada segundo segundo em C # .Alguma imagem não é criada corretamente mostrada em branco

Question

Abaixo, o comando é usado no loop para tirar um instantâneo no meu programa ffmpeg.exe -ss 720 -i WIn_0_0.wmv -vframes 1 -vf "[in]drawtext=fontsize=18:fontcolor=Red:fontfile='/Windows/Fonts/arial.ttf':text='0\:12\:0':x=(w)-75:y=(h)-20" WIn_0_0_60.jpg

O código acima tira o instantâneo em 00 segundos. Na execução em um loop, por vezes, recebo imagens como esta

Existealgumasoluçãopararesolverisso?Estoufazendo3600snapshotsem1horaevejocercade20a30snapshotscomoestefazendoaminiaturafinalparecerruim.

Aquiestáamensagemdoconsoleffmpeg

ffmpeg.exe-ss720-iWIn_0_0.wmv-vframes1-vf"[in]drawtext=fontsize=18:fontcolor=Red:fontfile='/Windows/Fonts/arial.ttf':text='0\:12\:0':x=(w)-75:y=(h)-20" WIn_0_0_60.jpg
ffmpeg version 2.0.1 Copyright (c) 2000-2013 the FFmpeg developers
  built on Sep 26 2013 01:50:16 with gcc 4.8.1 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetype --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
  libavutil      52. 38.100 / 52. 38.100
  libavcodec     55. 18.102 / 55. 18.102
  libavformat    55. 12.100 / 55. 12.100
  libavdevice    55.  3.100 / 55.  3.100
  libavfilter     3. 79.101 /  3. 79.101
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  3.100 / 52.  3.100
Input #0, asf, from 'C:\Users\CSK\Desktop\totest\Report\WIn_0_0.wmv':
  Metadata:
    WMFSDKNeeded    : 0.0.0.0000
    DeviceConformanceTemplate: @
    WMFSDKVersion   : 12.0.7600.16385
    IsVBR           : 1
    VBR Peak        : 604576
    Buffer Average  : 4021058
    encoder         : Lavf55.12.100
  Duration: 01:00:00.06, start: 0.000000, bitrate: 210 kb/s
    Stream #0:0: Video: wmv2 (WMV2 / 0x32564D57), yuv420p, 320x240, 14.58 tbr, 1k tbn, 1k tbc
Output #0, image2, to 'C:\Users\CSK\Desktop\totest\Report\WIn_0_0\WIn_0_0_60.jpg':
  Metadata:
    WMFSDKNeeded    : 0.0.0.0000
    DeviceConformanceTemplate: @
    WMFSDKVersion   : 12.0.7600.16385
    IsVBR           : 1
    VBR Peak        : 604576
    Buffer Average  : 4021058
    encoder         : Lavf55.12.100
    Stream #0:0: Video: mjpeg, yuvj420p, 320x240, q=2-31, 200 kb/s, 90k tbn, 14.58 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (wmv2 -> mjpeg)
Press [q] to stop, [?] for help
[wmv2 @ 024eeb80] warning: first frame is no keyframe
frame=    1 fps=0.0 q=0.0 Lsize=N/A time=00:00:00.06 bitrate=N/A dup=0 drop=12