title: extracting h264 raw video stream from mp4 or flv with ffmpeg generate an invalid stream
body: <p>I'm trying to extract the video stream from an mp4 or flv h264 video (youtube video) using ffmpeg. The original video (test.flv) play without trouble with ffplay , ffprobe gives an error as follow:</p>
  
  <pre><code>ffprobe version N-55515-gbbbd959 Copyright (c) 2007-2013 the FFmpeg developers
  built on Aug 13 2013 18:06:32 with gcc 4.7.3 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
  isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
  le-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp
  e --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --ena
  ble-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-l
  ibopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libsp
  eex --enable-libtheora --enable-libtwolame --enable-libvo-aacenc --enable-libvo-
  amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --
  enable-libxvid --enable-zlib
    libavutil      52. 42.100 / 52. 42.100
    libavcodec     55. 27.100 / 55. 27.100
    libavformat    55. 13.102 / 55. 13.102
    libavdevice    55.  3.100 / 55.  3.100
    libavfilter     3. 82.100 /  3. 82.100
    libswscale      2.  4.100 /  2.  4.100
    libswresample   0. 17.103 /  0. 17.103
    libpostproc    52.  3.100 / 52.  3.100
  [flv @ 000000000031ea80] Stream discovered after head already parsed
  Input #0, flv, from 'test.flv':
    Metadata:
      starttime       : 0
      totalduration   : 142
      totaldatarate   : 692
      bytelength      : 12286492
      canseekontime   : true
      sourcedata      : B42B95507HH1381414522145462
      purl            :
      pmsg            :
    Duration: 00:02:22.02, start: 0.000000, bitrate: 692 kb/s
      Stream #0:0: Video: h264 (Main), yuv420p, 640x268, 568 kb/s, 23.98 tbr, 1k t
  bn, 47.95 tbc
      Stream #0:1: Audio: aac, 44100 Hz, stereo, fltp, 131 kb/s
      Stream #0:2: Data: none
  Unsupported codec with id 0 for input stream 2
  </code></pre>
  
  <p>to get rid of the extra streams ( I only needs the video) I used the following ffmpeg command line:</p>
  
  <pre><code>ffmpeg -i test.flv -map 0:0 -vcodec copy -an -f h264 test.h264
  </code></pre>
  
  <p>The new stream is unreadable by any player including ffplay and gives an error with ffprobe :
  test.h264: Invalid data found when processing inputq=    0B f=0/0</p>
  
  <p>Any body have an idea about what am I doing wrong?</p>
  
  <p>I also tried simpler youtube command line:</p>
  
  <pre><code>ffmpeg -i test.flv -vcodec copy -an test.h264
  </code></pre>
  
  <p>if I use another format (avi for example): </p>
  
  <pre><code>ffmpeg -i test.flv -vcodec copy -an test.avi
  </code></pre>
  
  <p>the output video is valid. </p>
  
  <p>If I transcode the video </p>
  
  <pre><code>ffmpeg -i test.flv -an test.h264
  </code></pre>
  
  <p>the output is also valid</p>
  
  <p>Any suggestions?</p>