maneira de extrair a miniatura com valor q é mais de 5.0 no comando ffmpeg?

Question

Eu editei uma pergunta (obrigado por conselhos). Quando eu extraio uma miniatura do ffmpeg, posso receber uma mensagem como esta no final da mensagem.

# ffmpeg -ss 600 -i /home/juneyoungoh/Videos/T30644_19_120412.ts.pac -vframes 1 -y /home/juneyoungoh/aaaaaaaaaaaaaaaaaaa.jpg
ffmpeg version git-2013-05-31-9d56ccf Copyright (c) 2000-2013 the FFmpeg developers
  built on May 30 2013 21:34:51 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
  configuration: --extra-libs=-ldl --enable-gpl --enable-libass --enable-libfdk-aac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libopus --enable-libvpx --enable-x11grab --enable-libx264 --enable-nonfree --enable-version3
  libavutil      52. 34.100 / 52. 34.100
  libavcodec     55. 12.102 / 55. 12.102
  libavformat    55.  8.102 / 55.  8.102
  libavdevice    55.  2.100 / 55.  2.100
  libavfilter     3. 73.100 /  3. 73.100
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  3.100 / 52.  3.100
[h264 @ 0x32da920] Cannot use next picture in error concealment
[h264 @ 0x32da920] concealing 742 DC, 742 AC, 742 MV errors in P frame
[h264 @ 0x32da920] left block unavailable for requested intra4x4 mode -1 at 0 5
[h264 @ 0x32da920] error while decoding MB 0 5, bytestream (4350)
[h264 @ 0x32da920] Cannot use next picture in error concealment
[h264 @ 0x32da920] concealing 1174 DC, 1174 AC, 1174 MV errors in P frame
[h264 @ 0x32da920] left block unavailable for requested intra4x4 mode -1 at 0 18
[h264 @ 0x32da920] error while decoding MB 0 18, bytestream (1641)
[h264 @ 0x32da920] Cannot use next picture in error concealment
[h264 @ 0x32da920] concealing 589 DC, 589 AC, 589 MV errors in P frame
[h264 @ 0x32da920] left block unavailable for requested intra mode at 0 9
[h264 @ 0x32da920] error while decoding MB 0 9, bytestream (2331)
[h264 @ 0x32da920] Cannot use next picture in error concealment
[h264 @ 0x32da920] concealing 994 DC, 994 AC, 994 MV errors in P frame
[h264 @ 0x32da920] left block unavailable for requested intra mode at 0 22
[h264 @ 0x32da920] error while decoding MB 0 22, bytestream (269)
[h264 @ 0x32da920] Cannot use next picture in error concealment
[h264 @ 0x32da920] concealing 409 DC, 409 AC, 409 MV errors in P frame
[mpegts @ 0x32d68a0] max_analyze_duration 5000000 reached at 5013333 microseconds
Input #0, mpegts, from '/home/juneyoungoh/Videos/T30644_19_120412.ts.pac':
  Duration: 00:59:01.21, start: 10.000000, bitrate: 2309 kb/s
  Program 1 
    Stream #0:0[0x200]: Video: h264 (Main) ([27][0][0][0] / 0x001B), yuv420p, 720x480 [SAR 8:9 DAR 4:3], 29.97 fps, 29.97 tbr, 90k tbn, 59.93 tbc
    Stream #0:1[0x201]: Audio: aac ([15][0][0][0] / 0x000F), 48000 Hz, stereo, fltp, 187 kb/s
Output #0, image2, to '/home/juneyoungoh/aaaaaaaaaaaaaaaaaaa.jpg':
  Metadata:
    encoder         : Lavf55.8.102
    Stream #0:0: Video: mjpeg, yuvj420p, 720x480 [SAR 8:9 DAR 4:3], q=2-31, 200 kb/s, 90k tbn, 29.97 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (h264 -> mjpeg)
Press [q] to stop, [?] for help
[h264 @ 0x32da920] Missing reference picture, default is 0
[h264 @ 0x32da920] decode_slice_header error
[h264 @ 0x32da920] Cannot use next picture in error concealment
[h264 @ 0x32da920] concealing 686 DC, 686 AC, 686 MV errors in P frame
[h264 @ 0x32da920] left block unavailable for requested intra mode at 0 28
[h264 @ 0x32da920] error while decoding MB 0 28, bytestream (6046)
[h264 @ 0x32da920] Cannot use next picture in error concealment
[h264 @ 0x32da920] concealing 139 DC, 139 AC, 139 MV errors in P frame
[h264 @ 0x32da920] Cannot use next picture in error concealment
[h264 @ 0x32da920] concealing 830 DC, 830 AC, 830 MV errors in P frame
[h264 @ 0x32da920] left block unavailable for requested intra mode at 0 17
[h264 @ 0x32da920] error while decoding MB 0 17, bytestream (11936)
[h264 @ 0x32da920] concealing 634 DC, 634 AC, 634 MV errors in I frame
frame=    1 fps=0.0 q=5.0 Lsize=N/A time=00:00:00.03 bitrate=N/A    
video:23kB audio:0kB subtitle:0 global headers:0kB muxing overhead -100.091663%

Eu acho que esta parte "frame = 1 fps = 0.0 q = 5.0 Lsize = N / D tempo = 00: 00: 00.03 bitrate = N / A" mostra informações do arquivo de saída (neste caso, arquivo de imagem jpg).

O que estou procurando é a maneira de extrair miniaturas de arquivos de vídeo, apenas caso de "q > = 5.0". (Eu acho que isso 'q' significa qualidade. Eu sabia que existe uma opção 'q', mas pode ser tem um significado diferente)

1. vou acessar um determinado ponto do vídeo por meio da opção 'ss'.
2. Vou verificar se a qualidade do quadro está acima de 5.0 ou não.
3. Se sim, extraia a miniatura, caso contrário, o quadro mais próximo terá valor de qualidade superior a 5,0.

Posso fazer isso com a opção ffmpeg + linha de comando do Linux?