title: Can I concurrently read an earlier section of an mp4 file while streaming/writing into it?
body: <p>I am using Live555/openRTSP based code to stream an H.264 video source to an mp4 file, and would like to concurrently read the earlier parts of the file (from a different application). Changing the <code>fopen</code> to be <code>fid = _fsopen(fileName, "wb", _SH_DENYWR)</code> (from OutputFile.cpp) clearly isn't enough, because it makes no difference and the media players still won't open it (is that the write line for the mp4 output?)</p>
  
  <p>On a related note if I simulate an unclean shutdown of the software (e.g. power failure) the unfinished files are not readable by any media players. I assume that what is written to the file on file-close is what allows a media player to understand the file. This is also a situation I'd like to code for, if possible, and is quite likely the really the same problem as above?</p>
  
  <p>Any pointers/answers/thoughts greatly received :-)</p>