How about using the optimised versions of the ogg vorbis encoder by 'Blacksword'? Ive tried them and theyre almost twice as fast as the standard builds.
links:
http://homepage3.nifty.com/blacksword/
http://www.hydrogenaudio.org/forums/ind ... opic=29161
And I noticed the latest mediacoder is just using lame 3.98a2. I found optimised versions of lame 3.97b2 and 3.98a6 at http://www.rarewares.org/
These might help speed up the audio encoding process...
