Friends, I have a number of .mp4 videos encoded with 5.1 (6 Channel) AAC audio. I would like to end up with an .mp4 with AC3 5.1 and 2 channel AAC encoded for Dolby Prologic II (such as the way Handbrake will do when encoding a video using AC3 passthough). I do not need to re-encode the video. So... using Xilisoft's Video Converter, I can get myself a good 5.1 ac3 file from the original 5.1 (6 ch) AAC file. The problem is that I haven't found anything on the mac that gives me an DPLII encoded 2ch AAC. I can pop into Windows and use MEGUI and the Nero AAC encoder to encode, but as we all know, one doesn't really just "pop" into Windows unless you absolutely have to. So, is there a mac tool into which I can feed either a 5.1 ac3 file or a 6ch AAC file which will spit out a 2ch AAC file encoded for DPLII? Of course, once I get the ac3, aac, and video together, I can just use Subler to mux it all back up. Many thanks in advance!