[mythtv-users] Channel change script, PVR-150, and tinny audio

Nick Morrott knowledgejunkie at gmail.com
Wed Dec 13 00:53:01 UTC 2006

On 12/12/06, Paul Fine <pfine at comcast.net> wrote:
> I have set up my MythTV so that the composite input is from a second
> video source (the first source is analog cable), which I call VCR.  This
> video source has 1 channel (chennel 0).  I can now set up a manual
> recording on channel 0, start my VCR, and capture my Rocky and
> Bullwinkle collection onto my MythTV.
> I used
> http://www.gossamer-threads.com/lists/mythtv/users/227647#227647
> to set up this configuration.
> Unfortunately, I have the tinny audio problem.  I found I could correct
> the PVR-150 audio capture problem by issuing the v4l2-ctl command
> [root at oscar ~]# v4l2-ctl -d /dev/video1 --set-ctrl=audio_emphasis=2
> This worked both times I tried it.
> I am looking for a way to automatically issue the v4l2-ctl command when
> I start recording on my "VCR" input.  I was thinking that perhaps the
> channel changing script will do this for me.  In my configuration for
> this video source, the channel change script is set to "/bin/true".  If
> I changed the value to point at a script that ran the v4l2-ctl command,
> and then returned true, would that do what I wanted it to do?

As long as the channel change script returns quickly, it should work
as you intend. I use this trick with my PVR-150 in my 'real' LIRC
channel changer script. I'm using the older ivtvctl utility (2.6.16
kernel) and after issuing the necessary irsend commands to change
channel on my STB, I then issue an ivtvctl command to correct the

If you run a command in your script that does not return sufficiently
quickly, you need to set it to run in the background, so the channel
change script can return immediately to MythTV. If the channel change
script takes too long to return, MythTV will assume tuning has failed,
and the recording will then fail.


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