title: What's the difference with crf and qp in ffmpeg?
body: <p>After browsing around Google, I've came across this page about h264 encoding and discovered about qp. <a href="https://trac.ffmpeg.org/wiki/Encode/H.264" rel="noreferrer">https://trac.ffmpeg.org/wiki/Encode/H.264</a></p>
  
  <p>My questions are: What are the differences with crf and qp? Is it better to use qp over crf overall, or is it only if for using qp 0 for best lossless? Does qp have a known sensible setting if it's preferred? So far, I know crf has the default value of 23 while 18 is a sensible preferred increase in quality, although I don't understand why 18 wouldn't be default if better sensible lossless. Lastly, would changing either of them cause incompatibility with non-ffmpeg players or just qp?</p>
  
  <p>I'm converting from webm to mp4 by the way.</p>
  
  <p>I was going to test crf 23 and 18 and pick which is best but I can't seem to find any concrete information on this comparison or about qp.</p>