I have found in the past that VLC is heavy and slow, and sometimes struggles to render heavy videos showing green pixels. Lately I have had good results with it, but a long time ago I had to find an alternative and that was MPC-HC. It is an engine, and many other players use it's engine, like ExMplayer and my personal choice for some visual candy SMPlayer, which is basically MPC with a more user-friendly UI. It is very quick, reliable and codec independent. Besides it has a very useful feature: under 'Subtitles' menu there is an option 'Find subtitles at OpenSubtitles.org...'. As expected, searches the current file being played and displays the available subtitles on that website (you can determine your preferred language in the options or it displays all). After selecting one option it automatically downloads and loads it, displaying the subtitles in a matter of seconds. If it is out of sync you can try another one.