title: Embedding Metadata to H.264 encoded file
body: <p>I am currently developing an application which produces certain metadata with respect to preview frames coming from the camera. I can see this metadata being produced properly and I have no problems here.</p>
  
  <p>However, I have to embed this metadata to these frames of interest (frames are processed by a native algorithm to produce this metadata). I am using ffmpeg with x264 to encode  the frames into H.264. I have checked x264.h and some documentations but failed to find what I seek.</p>
  
  <p>My question is; is there any unused portion of H.264 syntax that  I can embed my metadata to encoded frames?  </p>
  
  <p>I hope I was clear enough. Thanks in advance.</p>