title: imporve the the quality of merged video ffmpeg flutter
body: <p>I used this command to merge two video clips, but the quality of output is too low. I have not used ffmpeg before I read about parameter <code>-crf 27</code> and <code>-preset veryfast</code> to improve the quality but dont know how to use them with this command. Any help would be appreciated.</p>
  <pre><code>'-y -i ${_storedVideoOne.path} -i
   ${_storedVideoTwo.path} -r 24000/1001 -filter_complex
   \'[0:v:0][0:a:0][1:v:0][1:a:0]concat=n=2:v=1:a=1[out]\' -map \'[out]\'
   $outputPath';
  </code></pre>