Wow, I didn't believe this would work but it did. Thank you so much!
I'm even able now to transcode 1080p movies in a reasonable manner.
There's just one thing that's not right.
Before I reinstalled everything with your recipe, I could check the "Keep DTS audio in stream" checkbox, and really get the DTS to the receiver, but now, when this is on, when a movie with DTS in its stream is supposed to appear, I'm only getting a blank black screen (no error message on the PS3) and that's it.
When I check it off, I'm able to watch DTS containing movies, and it appears that something is transcoding the DTS to DD (but it doesn't soundas nearly as good as DTS, just dull and I can't hear the surround channels).
I think I should mention: I wasn't able to install libcelt0, libffado1, libxvidcore4-dev, as they couldn't be found; I didn't install the Live555 libraries, as I didn't think it's relevant; I got ffmpeg-mt not from the specified repository, as it was unresponsive, but from "git://gitorious.org/~astrange/ffmpeg/ffmpeg-mt.git" .
Any idea what went wrong?