[mythtv] #5900 and AAC 5.1 audio

[Yeechang Lee]

Foo bum, I've run into a peculiar issue with your #5900 (with #5964
too, if it matters) upmixer. On my -fixes frontend with S/PDIF
passthrough to a 5.1 receiver, playing the _Simpsons_ movie trailer
with AAC 5.1 audio at the bottom of
<URL:http://www.h264info.com/clips.html> results in garbled audio that
sounds something like a propeller. I've heard of one other report of
no audio at all.

The bottom two _I am Legend_ trailers' audio (also AAC 5.1) is fine,
and my receiver says it's receiving Dolby D, but if I toggle the
upmixer on and off from the OSD menu the audio pauses a moment, and
the receiver message blinks before again saying Dolby D, as if the
audio signal changes. This tells me some upmixing is still going on,
which I thought shouldn't happen given the three trailers' native 5.1.

-- 
Yeechang Lee <ylee at pobox.com> | San Francisco CA US