Sort and convert mp4 by audio codec?

[chrispopp8]

I've been ripping my movie collection to my external hard drive so I can watch them on my Roku via Plex.

I've been ripping two audio layers per title when I can - 2 channel and 5.1.

Unfortunately, some of the titles I've ripped for 2 channel I used AC3 and I should have used AAC so I don't have to reply upon the plex server to transcode (which can cause playback "loading" issues)

Is there a way to

1. determine which files have 2 channel AC3
2. convert them easily without loss of picture quality
3. preserve the 5.1 channel AC3 layer in place

If I have to re-encode each title individually then so be it but I've got over 500 titles so there has to be a better way to determine which as AC3 for 2 channel and which does not.

Thanks,
Chris

[newpball]

If you are a bit computer savvy you could use mediainfo cli and with some grep you'd come a long way to fully automatize this.