[mythtv-users] No Display

Andy mizeraka at yahoo.com
Mon Feb 7 18:54:55 UTC 2011

Thanks for all the helpful advice.  I have become convinced, however, that my problem is a problem with the television as suggested by Greg and Jay.  If anyone knows how to get the audio signal "always on" either through Xorg.conf or ALSA, I would appreciate a nudge in the right direction.

This is why I am sure that it is not a problem with the resolution:
- Video comes on with any audio signal from any source (including when I play a YouTube through Firefox), which I surmise means that there is no change in the resolution of the video signal.
- I changed my audio settings (through the very cool new "scan for audio" feature) to put audio out to a boombox.  The audio came through fine, but the video signal did NOT switch on.  Which again leads me to believe, as Greg and Jay suggested, that the TV will not display without both audio and video streams over HDMI.

Hopefully I can get some help with TV settings from LG, other wise the easy solution will be to return it for a model that DOES display HDMI without an audio signal.  I will be carrying my mythtv box with me and demanding to hook it up before I purchase another TV.  Or again, if anyone knows how to get the audio signal "always on" either through Xorg.conf or ALSA, I would appreciate the help.


On 02/06/2011 10:39 AM, Jay Ashworth wrote:
> ----- Original Message 
>> From: "Andre"<mythtv-list at dinkum.org.uk>
Sounds like the TV is the issue then, it's a long shot but if you 
>> running nvidia v260 drivers it might be worth trying the two 
>> output modes now available. RGB is the default but YCrCb 
is now
>> selectable in nvidia-settings. I've seen various TVs behave 
>> differently when given YCrCb instead of RGB (sometimes called 
TV mode
>> rather than PC mode, although there's a little more to it 
than just
>> this).
> To me, off hand, this sounds 
> The TV expects that the bitstream on the HDMI cable will 
always include a
> video *and* an audio stream, *even if there's no audio 
in that stream*, and
> the video card on the PC *isn't generating an audio 
stream*, unless there's
> actual, y'know, audio to put there.  Therefore, 
the TV intemperately refuses
> to display the perfectly good 
> Finding a way, probably in the Xorg screen config, to 
force that card to
> send an audio stream all the time, will I think be 
the solution...
> if it's possible.  The people who work on the 
drivers for the card you have
> are probably the best people to be asking: 
this is probably going to be a
> general problem.

I think your card 
and hardware are fine.
Your earlier recounting of the problem was not quite 
clear to me, but it 
sounded like you can get a desktop, but that it 'goes 
away' when 
mythfrontend starts. If that is correct then the first step is to 
any autostarting of myth.

And CONFIRM that this is a myth 
problem and not an existing OS problem.

I have a 3 year old 37" LG 
flatscreen.  The HDMI inputs are *not* all 
the same. One of them is slightly 
different than the others and is the 
one the TV expects will be used for PC 
input. ( I pipe the audio output 
of myth directly to an amplifier and then 
to audio speakers and never 
have any sound from the TV when using myth...so 
I think this may be a 
misleading item.)

You might have to try each 
input in turn. THankfully the remote has that 
dedicated button in the top 
right corner! (Or the buttons on the side of 
the TV).

It seriously 
sounds like myth is forcing a resolution which the TV does 
not like or the 
video chipset will not accept and output.( But the 
desktop resolution is 
fine, if I read correctly)

If you can get a desktop screen and log in 
(without autostarting myth) 
then the hardware is all right as is the 
resolution settings *for the 

In which case, you need to 
get into Setup -> Appearance and set *myth's* 
resolution to something 
like 1024x768. If you cannot get into there 
without losing the signal, then 
you will have to poke the Settings table 

At a mysql 
console, try
mysql>  select * from settings where value like 
select * from settings where value like 

This should give you a largish number of rows. You are 
interested in the 
GuiResolution, GuiHeight/Width, VidModeHeight/Width and 

TVVidModeResolution entries which have screen size values. You need/want 

them to be 1920x1200 although you might want to test using 

In your particular case, the GuiVidMode, GuiHeight,GuiWidth 
entries are 
likely the culprit if this diagnosis is anywhere near correct. 
You will 
need to:

mysql> update settings set data = "1360x768" 
where value = "GuiResolution";

My LG TV would NOT accept 1368 or 780 as 
proper sizes. I need 1368 for 
width, and 768 for height. So you might need 
to use 1912 and 1192. (The 
30" Dell monitor at work is quite happy with 
1920x1200 though!).



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