title: Convert form 30 to 60fps by increasing speed, not duplicating frames, using FFmpeg
body: <p>I have a video that is incorrectly labelled at 30fps, it is actually 60fps and so looks like it's being played at half speed. The audio is fine, that is, the soundtrack finishes half way through the video clip. I'd like to know how, if possible to fix this, that is double the video speed, making it 60fps and meaning that the audio and video are synced. </p>
  
  <p>The file is H.264 and the audio MPEG-4 AAC.</p>
  
  <p>File details as given by ffmpeg, as requested:</p>
  
  <pre><code>ffmpeg version 0.8.9-6:0.8.9-0ubuntu0.13.10.1, Copyright (c) 2000-2013 the Libav developers
  built on Nov  9 2013 19:09:46 with gcc 4.8.1
  *** THIS PROGRAM IS DEPRECATED ***
  This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from './Tignes60fps.mp4':
    Metadata:
      major_brand     : mp42
      minor_version   : 0
      compatible_brands: isommp42
      creation_time   : 2014-01-13 02:23:09
      Duration: 00:08:33.21, start: 0.000000, bitrate: 5690 kb/s
      Stream #0.0(eng): Video: h264 (High), yuv420p, 1920x1080 [PAR 1:1 DAR 16:9], 5609 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc
  Metadata:
      creation_time   : 2014-01-13 02:23:09
      Stream #0.1(eng): Audio: aac, 48000 Hz, stereo, s16, 156 kb/s
  Metadata:
        creation_time   : 2014-01-13 02:23:09
  At least one output file must be specified
  </code></pre>