[popcornmix]

BTW, I tried to play a movie with flac (Lossless) audio on both Pi b+ and Pi2 B. The playback was really sluggish and audio was several seconds ahead. I tried all possible settings. OMXPlayer hardware support made it better but not enough to make it watchable.
Doesn't the DVDPlayer/OMXPlayer support flac?

FLAC should be fine. If you have a video that doesn't okay well, then produce a sample (e.g. 200MB), check problem still exists, and upload it (e.g. to dropbox or google drive).