[mythtv-users] correctly setting permission for /dev/video* ubuntu 12.04+myth

Michael T. Dean mtdean at thirdcontact.com
Thu Jun 14 13:53:58 UTC 2012


On 06/14/2012 09:08 AM, Allan Strand wrote:
> Hi All,
>
> Ubuntu 12.04 and MythTV 0.25.1
>
> I have a hdpvr that works fine with the exception of color balance. 
>  As documented multiple places, the device can be controlled with 
> 'v4l2-ctl' and this issue can be fixed.
>
> So I have a bash script to change the settings using this approach 
> that's called by my channel change script.
>
> Unfortunately, the script does not seem to run when channel changing, 
> though it does when I run from command line.
>
> I suspect this is a permission problem, so I added mythtv (the user 
> that runs the backend) to the video group on this machine and verified 
> that group permissions on /dev/video1 (pvr-150 on video0) allow both 
> reading and writing.
>
> Still there seems to be no change to the device.  Also, I'm not sure 
> where to find stderr output from the channel change script.  It does 
> not seem to appear in the mythbackend log.
>
> Any pointers to solutions to what must be a common problem?

Perhaps you're running it too early--before MythTV sets it device 
settings?  Try putting a sleep in the channel change script before the 
color-fix script is run.

Also, I think there's a fix for the "wrong colors with new HD-PVR 
firmware versions" available (in new kernels or something?).  Might want 
to just fix the issue, instead of working around it.

Mike


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