Plex app transcodes too much

Not too surprising I suppose, but any video with AC-3 gets transcoded. So titles that could stream without any changes (H.264 + AC3 or mpeg2 + AC3), get transcoded. From what I recall the TiVo Opera browser supports very narrow range of codecs so pretty much everything I have gets transcoded when using the Plex app. Haven't looked in detail at the transcode arguments to see if it does a remux when applicable, but I would guess it's doing a full transcode even when video codec is compatible.
On the plus side, the transcode quality looks pretty good at least.