sS ffmpeg_speedUpVideo(File inVideo, File outVideo, double factor) {
  double invFactor = 1/factor;
  ret ffmpeg("-i " + platformQuote(inVideo)
    + "-filter_complex " + platformQuote("[0:v]setpts=" + invFactor + "*PTS[v];[0:a]atempo=" + factor + "[a]")
    + "-map " + platformQuote("[v]")
    + "-map " + platformQuote("[a]")
    + " -y " + platformQuote(mkdirsForFile(outVideo)));
}