I'm trying to add subtitles to an avi file (on a mac), and have been using ffmpeg. It's working perfectly except when it comes to {/a6} coding to make text appear at the top of the screen (usually simultaneous with another line of text at the bottom of the screen). Whenever a {/a6} line appears in my encoded file it only shows the {/a6} text...overwriting the original line that was supposed to be at the bottom of the screen. Ffmpeg does not recognize the {/a6} at all.

Is there anything I can change to the coding to so that the text will show up encoded at the top of the screen? Or, is there another program that might handle the {/a6} better?