title: How to concat the mp3 file and webm file into a new webm file?
body: <p>There is a webm file that contains no audio. I want to merge an audio file with this video. I've tried the following command:</p>
  
  <pre><code>ffmpeg -i /home/test.mp3  -i /home/output.webm -vcodec copy -acodec copy /home/newtest.webm
  </code></pre>
  
  <p>And received the error:</p>
  
  <pre><code>Could not write header for output file #0 (incorrect codec parameters ?):         Invalid argument.
  </code></pre>