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

[Nick Rout]

On Fri, Aug 3, 2012 at 7:03 PM, Stephen Worthington
<stephen_agent at jsw.gen.nz> wrote:
> 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.


Yes similarly documented years ago, usually easiest found by searching
on "tinny audio pvr-150"