var s = @"ffmpeg -i source.webm -vf ""setpts=2.0 * PTS"" target.webm";
var commandLine = CommandLineSplitter.Default.ParseString(s);
var args = commandLine.GetArgs(); // -> ["ffmpeg"", "-i", "source.webm", "-vf", "setpts=2.0 * PTS", "target.webm"]