Trust Fm

I've found very simple solution of the problem. First check the fps of the avi-file. For 23.976 set the offset normaly, for 25 fps set the offset to about 120. This will move your subtitles to the visible area.

Samsung HT-X30/TX35 also supported (output header "XviD").
Finally - the decision of "very small subtitles"-problem.

Thanks!

Edit: But not every file works (by unknown reason).