iTunes subtitles encoding

Guys, I have a video file (avi) and its subtitles file (srt) on Bulgarian language (Cyrillic) in UTF8 encoding. With VLC player it shows fine the subtitles. But when trying to convert the avi to m4v itunes format (using several apps, line iFlicks2 and iSubtitles) it convert the movie file and add subtitles but when playing in iTunes - it shows wrong subs characters (unreadable).... and I cannot solve it to show the correct Cyrillic encoding. Any special instructions for iTunes subtitles encoding or how to open subtitles from srt file directly?