$ ffmpeg -ss 00:10:01.01 -i /media/music/summer.mkv -y -f image2 -vframes 1 screenshot6.png
ffmpeg version 0.8.6-4:0.8.6-0ubuntu0.12.04.1, Copyright (c) 2000-2013 the Libav developers
  built on Apr  2 2013 17:00:59 with gcc 4.6.3
*** THIS PROGRAM IS DEPRECATED ***
This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
[matroska,webm @ 0x985baa0] Estimating duration from bitrate, this may be inaccurate
Input #0, matroska,webm, from '/media/music/summer.mkv':
  Duration: 01:21:46.44, start: 0.000000, bitrate: 384 kb/s
    Chapter #0.0: start 0.000000, end 540.760000
    Metadata:
      title           : Chapter  1
    Chapter #0.1: start 540.760000, end 1387.120000
    Metadata:
      title           : Chapter  2
    Chapter #0.2: start 1387.120000, end 2223.760000
    Metadata:
      title           : Chapter  3
    Chapter #0.3: start 2223.760000, end 2767.000000
    Metadata:
      title           : Chapter  4
    Chapter #0.4: start 2767.000000, end 3574.120000
    Metadata:
      title           : Chapter  5
    Chapter #0.5: start 3574.120000, end 4261.840000
    Metadata:
      title           : Chapter  6
    Chapter #0.6: start 4261.840000, end 4814.680000
    Metadata:
      title           : Chapter  7
    Chapter #0.7: start 4814.680000, end 4906.440000
    Metadata:
      title           : Chapter  8
    Stream #0.0(eng): Video: h264 (High), yuv420p, 712x572 [PAR 64:45 DAR 11392:6435], PAR 253:178 DAR 23:13, 25 fps, 25 tbr, 1k tbn, 50 tbc (default)
    Stream #0.1(fre): Audio: ac3, 48000 Hz, 5.1, s16, 384 kb/s (default)
Incompatible pixel format 'yuv420p' for codec 'png', auto-selecting format 'rgb24'
[buffer @ 0x993f660] w:712 h:572 pixfmt:yuv420p
[avsink @ 0x9942ec0] auto-inserting filter 'auto-inserted scaler 0' between the filter 'src' and the filter 'out'
[scale @ 0x9949d80] w:712 h:572 fmt:yuv420p -> w:712 h:572 fmt:rgb24 flags:0x4
Output #0, image2, to 'screenshot6.png':
  Metadata:
    encoder         : Lavf53.21.1
    Chapter #0.0: start 0.000000, end 786.110000
    Metadata:
      title           : Chapter  2
    Chapter #0.1: start 786.110000, end 1622.750000
    Metadata:
      title           : Chapter  3
    Chapter #0.2: start 1622.750000, end 2165.990000
    Metadata:
      title           : Chapter  4
    Chapter #0.3: start 2165.990000, end 2973.110000
    Metadata:
      title           : Chapter  5
    Chapter #0.4: start 2973.110000, end 3660.830000
    Metadata:
      title           : Chapter  6
    Chapter #0.5: start 3660.830000, end 4213.670000
    Metadata:
      title           : Chapter  7
    Chapter #0.6: start 4213.670000, end 4305.430000
    Metadata:
      title           : Chapter  8
    Stream #0.0(eng): Video: png, rgb24, 712x572 [PAR 253:178 DAR 23:13], q=2-31, 200 kb/s, 90k tbn, 25 tbc (default)
Stream mapping:
  Stream #0.0 -> #0.0
Press ctrl-c to stop encoding
frame=    1 fps=  0 q=0.0 Lsize=      -0kB time=0.04 bitrate=  -4.4kbits/s dup=0 drop=45    op=40
video:810kB audio:0kB global headers:0kB muxing overhead -100.002652%