title: Using ffmpeg with not consecutive numbered files
body: <p>I am using ffmpeg to produce a video starting from a set of png images. However, the images I have are numbered like this:</p>
  
  <pre><code>image_D5_C0_F4.png
  image_D10_C0_F4.png
  image_D15_C0_F4.png
  image_D20_C0_F4.png
  </code></pre>
  
  <p>and so on. Basically, everything remains the same, but the inner part changes. My ffmpeg command looks like this:</p>
  
  <pre><code>ffmpeg -framerate 8 -start_number 5 -i img/image_%02d_C0_F4.png -c:v libx264 -r 30 -s 1200x900 -pix_fmt yuv420p out.mp4
  </code></pre>
  
  <p>but obviously it does not work. I looked into the manual to find an option that allow me to specify a starting number (5 in this case) and a standard increment (again, 5), so to catch 5,10,15,20 etc.</p>
  
  <p>Any idea on how to solve this? I know I can handle everything with a script to rename all the files, but I wanted to check whether ffmpeg has the needed option in the first place.</p>
  
  <p>Thanks</p>