title: ffmpeg - resize video and merge with image
body: <p><img src="https://i.stack.imgur.com/ZFx0h.png" alt="Attached Image"></p>
  
  <p>I've 3 inputs (1st, 2nd and 3rd block)<br>
  1st a mp4 video with 600x400 aspect ratio<br>
  2nd a png image with 600x400 aspect ratio<br>
  3rd a jpeg image with red background  </p>
  
  <p>Output (4th block)</p>
  
  <p>I need a mp4 video of 600x400 as output, it should have resized video of 422x282 and merge all three as shown in image.  </p>
  
  <p>Can we implement this via ffmpeg command line?<br>
  I'm able to resize video and image separately but having issue in creating desire output.  </p>