Width keeps being fixed to 408px no matter what

[Vincent]

Version information

• fluent-ffmpeg version: 2.1.2
• ffmpeg version: 2.1.2
• OS: Windows

Code to reproduce

    ffmpeg()
      .input(pngPath)
      .inputOptions('-loop 1')
      .duration(OUTRO_DURATION)
      .videoFilters(`scale=${width}:${height},setsar=1`)
      .output(outroPath)
      .on('end', resolve)
      .on('error', reject)
      .run();

(note: if the problem only happens with some inputs, include a link to such an input file)

Expected results

pngPath has a width of 420px, however no matter what the final output outroPath will have width of 408px. I have tried doing size('420x600') or videoFilters(scale=420:600,setsar=1) but nothing...

Observed results

The width is always 408px