leo@chessman ~ :( $ ffmpeg -f v4l2 -input_format mjpeg -video_size 1280x720 -i /dev/video0 -c copy image%4d.jpg
ffmpeg version N-57228-g71f73ee Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)
  configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-shared --disable-static --enable-avresample --enable-vda --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libcaca --enable-libcdio --enable-libdc1394 --enable-libfdk-aac --enable-libflite --enable-libfreetype --enable-libgme --enable-libgsm --enable-libiec61883 --enable-libmp3lame --enable-libopus --enable-libpulse --enable-libquvi --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-openal --enable-opencl --enable-opengl --enable-openssl --enable-sdl --enable-x11grab --enable-zlib --enable-pic
  libavutil      55. 13.100 / 55. 13.100
  libavcodec     57. 22.100 / 57. 22.100
  libavformat    57. 21.101 / 57. 21.101
  libavdevice    57.  0.100 / 57.  0.100
  libavfilter     6. 23.100 /  6. 23.100
  libavresample   3.  0.  0 /  3.  0.  0
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
[mjpeg @ 0x12adee0] Changing bps to 8
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 671718.926317, bitrate: N/A
    Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 1280x720, -5 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
Output #0, image2, to 'image%4d.jpg':
  Metadata:
    encoder         : Lavf57.21.101
    Stream #0:0: Video: mjpeg, yuvj422p, 1280x720, q=2-31, -5 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
[image2 @ 0x12af040] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 19911985 >= -7742614
[image2 @ 0x12af040] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 19911985 >= 93392
[image2 @ 0x12af040] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 19991830 >= 206605
[image2 @ 0x12af040] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 20028527 >= 276327
[image2 @ 0x12af040] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 20028527 >= 671005
[image2 @ 0x12af040] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 20028527 >= 401260
[image2 @ 0x12af040] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 20028527 >= 463507
[image2 @ 0x12af040] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 20028527 >= 533951
[image2 @ 0x12af040] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 20028527 >= 597478
[image2 @ 0x12af040] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 20028527 >= 677893
[image2 @ 0x12af040] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 20028527 >= 742563
frame=   16 fps=0.0 q=-1.0 Lsize=N/A time=00:00:20.02 bitrate=N/A speed=23.2x
video:3094kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Exiting normally, received signal 2.
leo@chessman ~ :( $ ls *.jpg
image0001.jpg  image0005.jpg  image0009.jpg  image0013.jpg  image0017.jpg  image0021.jpg  image0025.jpg  image0029.jpg  image0033.jpg  image0037.jpg  image0041.jpg  image0045.jpg
image0002.jpg  image0006.jpg  image0010.jpg  image0014.jpg  image0018.jpg  image0022.jpg  image0026.jpg  image0030.jpg  image0034.jpg  image0038.jpg  image0042.jpg  image0046.jpg
image0003.jpg  image0007.jpg  image0011.jpg  image0015.jpg  image0019.jpg  image0023.jpg  image0027.jpg  image0031.jpg  image0035.jpg  image0039.jpg  image0043.jpg  image0047.jpg
image0004.jpg  image0008.jpg  image0012.jpg  image0016.jpg  image0020.jpg  image0024.jpg  image0028.jpg  image0032.jpg  image0036.jpg  image0040.jpg  image0044.jpg  image0048.jpg
leo@chessman ~ :) $