private void RunFfMpegThumbnail(string filename)
{
Process process = new Process();
// Configure the process using the StartInfo properties.
process.StartInfo.FileName = FfmpegExecutable;
// make img 64x36 every 0.5 sec
// source: https://trac.ffmpeg.org/wiki/Create%20a%20thumbnail%20image%20every%20X%20seconds%20of%20the%20video
process.StartInfo.Arguments = String.Format("-i \"{0}\" -y -f image2 -vf \"scale={2},fps=fps=1/{3}\" \"{1}/out%d.jpg\"", filename, TempFolder, ThumbW + ":" + ThumbH, ThumbIntervalSec.ToString(CultureInfo.InvariantCulture));
process.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
process.StartInfo.CreateNoWindow = true;
runProcessRememberError(process);
}