title: GIF muxer supports only a single video GIF stream
body: <p>so I'm trying to watermark a folder full of gifs but I get an error saying that I can only work with one GIF stream at the time, is there a way to circumvent this?</p>
  
  <pre><code>@echo off
  setlocal
  for %%G in ("%~dp0gifs\*.gif") do (
      ffmpeg -i %%G -i Watermark.png -filter_complex "[0:v]scale=trunc(iw/2)*2:trunc(ih/2)*2[v0];[1:v][v0]scale2ref=trunc(iw/5):trunc(ih/16)[logo][0v];[0v][logo]overlay=W-w-3:H-h-4 [v]" -map "[v]" -codec:v libx264 -preset slow -crf 18 %%~nG.gif
      )
  )
  endlocal
  pause
  </code></pre>
  
  <p>The error from <code>ffmpeg</code>:</p>
  
  <pre><code>[gif @ 0x7ff212801c00] GIF muxer supports only a single video GIF stream.
  Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument
  Error initializing output stream 0:0 -- 
  </code></pre>