[mythtv-users] No Display

[R. G. Newbury]

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 are
>> running nvidia v260 drivers it might be worth trying the two different
>> output modes now available. RGB is the default but YCrCb is now
>> selectable in nvidia-settings. I've seen various TVs behave quite
>> 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 like:
>
> 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 video.
>
> 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 stop 
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 
desktop*.


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 
directly.

At a mysql console, try
mysql>  select * from settings where value like "%Vid%";
and
select * from settings where value like "%Resolution%";

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 1024x768.

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!).

HTH

Geoff