Adding a logo watermark to a video

function convert(input, output, callback) {
  if (debug) {
    console.log("CONVERTING");
    console.log("IN: " + input);
    console.log("OUT: " + output);
  }
  ffmpeg(input)
    // Adding a logo watermark
    .input("clipdrop_logo.png")
    // Set the logo positions
    .complexFilter([
        "overlay=main_w-overlay_w-50:main_h-overlay_h-50",
    ])
    .outputOptions([
      "-loglevel panic",
      "-preset veryfast",
      "-movflags faststart",
      "-vf scale=-1:480",
      "-c:v libx264",
      "-crf 23",
      "-c:a aac",
      "-bitrate 2000000",
      "-maxrate 2200000",
      "-bufsize 1500000"
    ])
    .on("end", function () {
      if (debug) {
        console.log("conversion ended");
      }
      callback(null);
    })
    .on("error", function (err) {
      if (debug) {
        console.log("error x: ", err);
      }
      callback(err);
    })
    .saveToFile(output);
}