title: File concat error using ffmpeg
body: <p>I am trying to concat two files using ffmpeg. I have a file input.txt where I have written</p>
  
  <pre><code>file "1.mpg"
  file "2.mpg"
  </code></pre>
  
  <p>and the command i am using  </p>
  
  <pre><code>ffmpeg -f concat -i input.txt -codec copy output.mpg
  </code></pre>
  
  <p>but i am keep getting this error impossible to open \1.mpg and input.txt: Invalid argument.</p>
  
  <p>any help will be appreciated </p>