[mythtv-users] amplifier power control

[Shawn Rutledge]

Finally, last night, several years of frustration ended with me
finally getting useable ATSC HD video out of my MythTV box.  Complete
with digital audio, from the cx88_alsa module, even!  After I gave up
on the onboard ATI video for now and put an nVidia board in, it's nice
and smooth, and the dual-core CPU is fast enough to not bother with
XvMC.  (But I still hope the ATI drivers will get Xv support in a few
months, and then I can go back to it, because it will take less
power.)  I got an Apple Bluetooth keyboard to use as a remote (it will
have other uses) and that's working fine too; as advised on some
Gentoo page I set it up in /etc/conf.d/bluetooth to run hidd --connect
<bdaddr> on startup, so it "just works" after the pairing has been
done the first time.  (It would be nice to have a Myth module to
search for and pair Bluetooth peripherals, though.  It should use the
BlueZ v3 APIs and/or dbus to accomplish that.  hidd is supposed to be
obsolete now.)

So the next thing I'm thinking is how to make it more friendly for my
wife to turn on the rest of the stuff to watch TV.  Well the projector
has a serial port, so in theory I could automatically turn it on and
off.  (What to use as the main system "power" button still needs some
thought.  Some key combination, maybe.)  If I have audio from legacy
components (such as the old VCR and laserdisc player) all passing
through the computer's line in (yes that will degrade the audio
somewhat) then there could be complete software control of the source
switching (tell the projector to take composite input, and tell the
sound card to pass through the line input, at the same time).  The
sound card's mixer could be the main audio control and I could use a
simple block amplifier rather than a receiver, so you always use the
keyboard to adjust the volume. There could be a simple Myth module to
select other sources and control the volume, maybe even do
visualizations the way MythMusic does.  Another way I was thinking is
to get a 1U stereo mixer and equalize the volumes between sources, so
that you will always hear audio from every component without having to
switch anything.  (Just have to turn off the ones you aren't using.)
But again it would lead to more total system noise.

Anybody know of a project to turn an amplifier on and off based on
whether there is any audio going through the ALSA device?  It could be
a separate app which listens to the device, and uses some sort of USB
or parallel-port relay to turn the amp on, and then back off after 5
minutes of silence or so.