[mythtv-users] LG TV starts flickering when using LiveTV

[Stephen Worthington]

On Tue, 27 Feb 2018 21:21:58 -0600, you wrote:

>On 02/26/2018 10:13 PM, Stephen Worthington wrote:
>> On Mon, 26 Feb 2018 21:11:31 -0600, you wrote:
>>
>> I would have thought that it was more likely a particular channel or
>> program caused this sort of problem, rather than live TV versus
>> recorded TV.  It is usually caused by trying to overclock the TV,
>> which is usually caused by the TV giving the video card bad EDID data.
>> The fix is usually to manually configure the available X video modes -
>> a painful process.  Or to copy and manually edit the EDID data -
>> equally painful.  But it may be possible to override the settings in
>> mythfrontend for a particular frame size, if you can identify that as
>> the problem.
>>
>> When playing video that works, take a look at what M(enu) > Playback
>>> Playback data shows for the video output, particularly the frame size
>> and frame rate.  You can also install mediainfo and use it to read out
>> the same data from the file.  Pressing I twice while a recording is
>> selected will tell you the file name to use with mediainfo.  While
>> playing the video or recording or live TV, Alt-Tab to a command prompt
>> on the desktop and run xrandr to see what video mode the video card is
>> set to output at the moment.  Here is what I get from an NTSC movie
>> file:
>>
>> Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 8192 x 8192
>> DVI-I-0 disconnected (normal left inverted right x axis y axis)
>> VGA-0 disconnected (normal left inverted right x axis y axis)
>> DVI-I-1 connected primary 1920x1080+0+0 (normal left inverted right x
>> axis y axis) 1600mm x 900mm
>>    1920x1080     60.00 +  59.94*   50.00    23.97    60.05    60.00
>> 50.04  
>>    1280x1024     60.02  
>>    1280x720      60.00    59.94    50.00  
>>    1024x768      60.00  
>>    800x600       60.32  
>>    720x576       50.00    50.08  
>>    720x480       59.94    60.05  
>>    640x480       59.94    59.93  
>> HDMI-0 disconnected (normal left inverted right x axis y axis)
>>
>> You can see it is playing at just under 60 Hz, correct for
>> deinterlaced NTSC movies.
>>
>> And this is from an HD recording from DVB-T:
>>
>> Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 8192 x 8192
>> DVI-I-0 disconnected (normal left inverted right x axis y axis)
>> VGA-0 disconnected (normal left inverted right x axis y axis)
>> DVI-I-1 connected primary 1920x1080+0+0 (normal left inverted right x
>> axis y axis) 1600mm x 900mm
>>    1920x1080     60.00 +  59.94    50.00*   23.97    60.05    60.00
>> 50.04  
>>    1280x1024     60.02  
>>    1280x720      60.00    59.94    50.00  
>>    1024x768      60.00  
>>    800x600       60.32  
>>    720x576       50.00    50.08  
>>    720x480       59.94    60.05  
>>    640x480       59.94    59.93  
>> HDMI-0 disconnected (normal left inverted right x axis y axis)
>>
>> Our TV is 50 Hz, and the output frequency has been changed to that.
>>
>> Do these checks on things that work, then try the live TV that does
>> not and see what video mode it is using.  You should be able to
>> identify a video mode that is causing the problem, and then we can see
>> if it is possible get mythfrontend to map that to a different video
>> mode, or whether you will need to set up manual X config.
>>
>> Also, what Nvidia driver version are you using?  I think there can be
>> problems with the latest drivers where the mode commands that
>> mythfrontend sends do not match what the drivers do any more, as they
>> redefined how those commands work a bit to accommodate 4K and other
>> new things.  I have an older card (Nvidia 220) and have to use older
>> drivers with it (340.104), so I do not get those problems.
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>
>Thanks for the tips. The playback data ('M' button) shows a
>Video:1920x1080 at 25.00fps. Unfortunately, this is a remote machine which
>I manage through vnc. Alt+Tab doesnt work on VNC, instead is trapped by
>the client.  I am looking into workaround for that. One thing I have
>noticed is that if I start using mythfrontend -w -geometry 800x600, the
>LiveTV works fine. Normally i using evilwm as a window manager with
>mythfrontend as fullscreen. The nvidia driver i am using is
>nvidia-drivers-387.22.

Yes, Alt-Tab does work with VNC, with the right client.  My TightVNC
client on Windows has an Alt button on its toolbar.  Check the
documentation for your client - they often have a key like F8 to bring
up a menu with that sort of option on it.

In any case, it is possible to get xrandr to talk to the display via
ssh, with the right options.  You have to be logged in via ssh using
the same username as the desktop is running under, then use this
command:

xrandr -d :0.0

That version of the Nvidia drivers is recent enough for it to
potentially have the problem I have seen reported.  I think all the
387 and above versions have it.  But as my Nvidia cards are too old to
run with the 387 drivers, I can not test and see.