title: How to compose 2 videos by using FFmpeg hstack filter?
body: <p>I want to compose 2 videos into 1 video by putting side by side.
  I also hope to set start/stop time for each video.
  Final video should be H264/AAC codec and mp4 format.
  I attached sample videos.
   <a href="https://www.dropbox.com/s/e5eouyrrqsy44ts/1.webm?dl=0" rel="nofollow">https://www.dropbox.com/s/e5eouyrrqsy44ts/1.webm?dl=0</a>
   <a href="https://www.dropbox.com/s/u0zqie0icxamt3q/2.webm?dl=0" rel="nofollow">https://www.dropbox.com/s/u0zqie0icxamt3q/2.webm?dl=0</a></p>
  
  <p>I used the following ffmpeg command.</p>
  
  <p><strong>ffmpeg -i 1.webm -i 2.webm -filter_complex "[0:v][1:v]hstack" output.mp4</strong></p>
  
  <p>When I run this command on Terminal of Mac OS X 10.11, It gave me the following error.</p>
  
  <p><strong>Input 1 height 480 does not match input 0 height.</strong></p>
  
  <p>The video are from smartphone, so its orientation is not correct.
  Please help me to make composed video with FFmpeg.</p>