Blurry Display (Panasonic TC-L42E60)

[Felix Miata]

On 2013-07-09 15:16 (GMT-0400) Steven Blatchford composed:

>>Your laptop screen is 1366x768, right?

> Yes

>>Swapping between that and 1920x1080 can be problematic.

> I have been using the older 42" for the past six months without issue.
> I was connected to it via a VGA cable.  I have tested HDMI to the older
> 42" and it works fine.

So the two 42s work identically except for the "blurriness" of the new 
Panasonic, and same whether using VGA, DVI or HDMI cable? Or, are objects 
obviously differently sized on the two 42s?

>>Which DE are you running at what version?

> I'm not using a DE, just a WM (dwm).

Not one I've ever used. Which distro?

>>What do Firefox or SeaMonkey report if you open
>>http://fm.no-ip.com/Auth/dpi-screen-window.html ? Does what either
>>report make sense to you?

> laptop - http://i1.minus.com/ibfQOuUqdCVVLo.png I measured the black box
> and it is an inch.  Those numbers look correct to me.

> 42_old - http://i2.minus.com/iQUKGjZbRMiNz.png I measured the black box
> and it is *not* an inch, it's 2".  The other numbers look correct to me.

When desktop density is less than 96 DPI, Geckos (like most web browsers) 
force a minimum DPI of 96 unless you alter a hidden preference referred to at 
that URL. Computer fonts can get ugly or even unintelligible at anything much 
less than 96. Most fonts are tuned to 96, but work similarly well only at 
multiples of 12, better yet at multiples of 24. Physical DPI of a 42" 
1920x1080 screen is about 52.4.

On my 31.5" Vizio 1080p, which is 700mm wide and about 69.9 DPI, that block 
is 19/16" wide. I would expect that block on either of your 42" to measure 
930mm / 700mm * 19 / 16 = or just over 25/16" (1.5777") wide.

It seems that your TV and probably its EDID thinks it's a ~32" screen model, 
which easily could result in blurriness on an actual 42" screen. If your free 
return period on that Panasonic hasn't expired yet and you're not married to 
it, I'd take it back and get something else. At least try an exchange in case 
it's an individual defect rather than a model defect.

>>Does 'xrdb -query | grep dpi' report anything? If so, what?

> I get no output from 'xrdb -query'

Fine. Some distros unconditionally force DPI to 96 via Xft.dpi. If set, xrdb 
-query would report it.

>>Do xdpyinfo resolution and dpi match xrandr output?

> $ xdpyinfo | grep -B1 resolution    # laptop
>    dimensions:    1366x768 pixels (277x156 millimeters)
>    resolution:    125x125 dots per inch

OK

> $ dtsteve:~/ xdpyinfo | grep -B1 resolution     # new 42"
>    dimensions:    1920x1080 pixels (696x391 millimeters)
>    resolution:    70x70 dots per inch

70x70 and 696x391 are what should be reported for a 32" TV, not a 42".

cf. http://fm.no-ip.com/PC/displays.html & http://fm.no-ip.com/PC/dpi.xhtml

>>Maybe you should upload Xorg.0.log from using each of the three
>>displays so we can compare?

> Here is my Xorg.0.log from yesterday -- http://sprunge.us/LNAT

Rather big and mixed, so not very useful to someone like me.

> I can work on compiling these three logs.  From a cold start, you want
> me to
>      - boot to X using the laptop and save the log
>      - boot to X using the new 42" and save the log
>      - boot to X using the old 42" and save the log

> Is this right?

I'd probably do the new 42 last, but yes. And just start a session and quit 
so as to save while small as possible.

>>The new TV may have defective EDID. Does its behavior change between
>>connecting it after boot and X startup, or before?

> Here is the EDID information connecting the HDMI cable after boot but
> before running X:
> get-edid | parse-edid -- http://sprunge.us/Jiig

 From that file:

parse-edid: parse-edid version 2.0.0
parse-edid: EDID checksum failed - data is corrupt. Continuing anyway.
parse-edid: first bytes don't match EDID version 1 header

It thinks there's a problem. I believe it.

> I've never tried booting with the HDMI cable plugged in nor have I tried
> running X and then plugging in the HDMI cable.  I can try those two
> scenarios.  Before doing anything else, I'll wait for your direction.

You may be able to get around your problem using an xorg.conf file (or 
xrandr) to override EDID. I do it more often than not, regardless whether 
EDID is good or not, usually to force my choice of DPI via DisplaySize. 
However, it's not so simple a task to set up xorg.conf on multi display 
systems. See:

http://fm.no-ip.com/Share/DisplaySize and
http://fm.no-ip.com/Tmp/Linux/Xorg/xorg.conf-dualheadminimal

For KDE 4.11 users it's supposed to be a lot simpler to get set up the way 
you want. Check out KScreen on KDE's site.
-- 
"The wise are known for their understanding, and pleasant
words are persuasive." Proverbs 16:21 (New Living Translation)

  Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata  ***  http://fm.no-ip.com/