title: ffmpeg - Input link in1:v0 parameters (size 640x640, SAR 16:9) do not match the corresponding output link in0:v0 parameters (640x640, SAR 427:240)
body: <p>I'm trying to concat 4 mp4 files. I'm using the command below but not able to concat</p>
  
  <pre><code>ffmpeg -i new1.mp4 -i new2.mp4 -i new3.mp4 -i new4.mp4 -filter_complex concat=n=4:v=1:a=1 output.mp4
  </code></pre>
  
  <p>Getting this error : </p>
  
  <pre><code>Input link in1:v0 parameters (size 640x640, SAR 16:9) do not match the corresponding output link in0:v0 parameters (640x640, SAR 427:240)
  </code></pre>
  
  <p>All four vides has the same codec and same size (640x640) and the same bitrate (30)</p>
  
  <p>What I am doing wrong?</p>