I personnaly exntended JW Player 5.10 source code in order to pan audio channels via Java Script API for bilingual encoded video files which are encoded that, for example, left side audio is Japanese and right side audio is English. 
Details of my personal extension is posted to JW player's forum, please see below.

How to extend JW Player to make audio to be panned via JavaScript API. 
http://www.longtailvideo.com/support/forums/jw-player/javascript-interaction/28334/how-to-extend-jw-player-to-make-audio-to-be-panned-via-javascript-api

I don't ensure workness and stability of it and don't do any supports for using it. Use it as your own risks. 

I strongly recommend getting original source code from LongTail's archives, patching accroding to above post and rebuilding player.swf BY YOURSELF. I don't do also any supports for this procedure. 

But just for your convinience and trial, rebuilded player.swf is placed in this zipped file. 
This zipped file includes exntended and rebuilded player.swf, jwplayer.min.js and so on. 

This extended JW Player is available just for non-commerical use. 
You absolutely can't use it for commercial use. 
To confirm defitions of commercial use, you have to read LongTail's readme.html and license.txt. Visit a folder '.\readme_from_longtail\'.
