I’m not sure if roku fully supports 5.1 or not, but I can tell you that if your 5.1 system has a pro logic setting the 2.0 tracks will still give great surround. They are matrix encoded to be compatible with dolby surround/pro logic and you will get legitimate surround, as in actual surround effects where they are supposed to be not just ambience. Use movie mode. In fact the 5.1 mixes present in de specialized are basically just doctored pro logic mixes anyway.
Some players don’t know what to do with DTS-MA audio in an MKV (even if they deal with it fine in other media formats). Converting to AC3 will give you a (lossy) 5.1 track. Burning to a Blu-ray will give you a lossless 5.1 track, but not in an MKV. Or you could try PC software playback, etc.
Understood. Thank you guys. Yeah, my 5.1 doesn’t really play back in lossless, so I’ll try AC3 first. If that doesn’t work, then Pro Logic (that was DEFINITELY mention in the manuel). Thank you Possessed and Catbus.