I don't have trouble playing mkvs in my sony bdp-s480 player, but when i skip chapters that's where the issue occurs, unlike the container mp4 i don' have problem skipping chapters, it seeks fast! but the problem is the bd player can't read subs internal or external (with same filename) in mp4. Now with Mkv the player can read the subs nicely, the chapter problem is whenever i press next to skip to the next chapter for example chapter 2, it won't go to chapter 2, instead it will start again on the current chapter which is chapter1. What wrong with it? To resolve the problem i have to re-encode it in handbrake! But i don't want to re-encode a big filesize like 6gb, it will take forever! So what i do is remux the elem.streams to mkv, but this problem is giving me headache, so i wish someone could point me out to the right direction. also skipping chapters is done after every seconds, so if you're chapter skipping you have to always wait 10 sec. to chapter skip, that's very lame.