Help with mkv and subtitles in media player classic?

i use media player classic to watch any and every video, i'm being forced to use the overlay mixer because any other output makes the video entirely too slow, but, the overlay mixer won't display the subtitles, and when i try anything that DOES show subtitles, the audio runs ahead of the video and the video is very very jumpy, i cant offset the audio because it changes how off set it is depending on how fast my computer will display the video. any other outputs i can use to watch high def mkvs with subtitles without the glitchiness? thanks