My apologies for being over polite. I should have just said what I tried and found. "I do not think..." should have been "I tried and I cannot get it to work, but I'm not perfect so I don't want to commit to saying it that way."
Using Handbrake to create the files, all settings are the same, but when MKV is the container, it will not load. Same movie, same settings as MP4, works fine. Problem is that Blu-ray PGS subtitles cannot be stored in MP4, only MKV. MP4 does permit the audio tracks.
The FFMpeg project does work directly out of XCode, but I am far far far from being able to move something like that into a library component for B4i. If anyone wishes to tackle it, contact me to arrange a contract.