[mythtvnz] PVR-150 / PVR-250 audio distortion bug workaround

[Stephen Worthington]

I record from my Sky decoder using the S-Video input on a Hauppauge
PVR-250 card.  My mother records FM radio using a PVR-150's FM tuner
on her MythTV box.  Both of us get recordings fairly frequently where
the audio suffers from nasty distortion - the real audio is there, but
mixed with other nasty sounds that usually make it impossible to
listen to the recordings where it happens.  Today I discovered this
page:

  http://urlgrey.net/?p=231

which has a workaround that seem to work.  What it does is to wait
until the recording has started, then issue a command to the card to
select audio input 1.  I tried this on my mother's box, and on the
second try at using live TV to listen to FM, I got the distorted
audio.  Then I manually issued the command, and the distortion went
away.

What I think may be happening is that more than one audio input is
being routed into the audio output, so you get the wanted audio plus
noise from an audio input that is not connected to anything.  The
workaround re-selects just the wanted input.

So now I am off to update both our tuning scripts to automate the
workaround by forking off a script to issue the command.  I am going
to use a "sleep 10" so that there will be some distortion at the
beginning of recordings if the bug occurs, and I will then be able to
tell if the fix works.