title: FFmpeg: what does the "global_header" flag do?
body: <p>According to the description, it <em>places global headers in extradata instead of every keyframe</em>.</p>
  
  <p>But what's the actual purpose? Is it useful e.g. for streaming?</p>
  
  <p>I guess that the resulting video file will be marginally shorter, but more prone to corruption (no redundancy = file unplayable if main header corrupted or only partially downloaded)?</p>
  
  <p>Or maybe it somehow improves decoding a little bit? As headers are truly global and cannot change from keyframe to keyframe?</p>
  
  <p>Thanks!</p>