[mythtv-users] Monitor adustment with SMPTE bars/ was: color adjustment

[Devin Heitmueller]

On Tue, Jan 26, 2010 at 11:28 PM, Brian Wood <beww at beww.org> wrote:
> On Tuesday 26 January 2010 08:51:08 pm Bob wrote:
>> I have my mythtv system connected to my TV via a standard "VGA"
>> connector.  The colors are off a bit, any suggestions on how to get them
>> closer?  I have a blue filter and a color bar pattern available to me.
>
> I've never tried using one of those filters, but assuming it gives the same
> effect as killing the red and green guns, this is what we used to do with
> analog monitors. Probably doesn't apply to LCD or Plasma panels:
>
> First question: what kind of bars so you have available?  Real ones? you want
> EIA bars at a minimum, and preferably split SMPTE bars. A PLUGE signal is a
> plus. Bars produced by a camera, or off tape, or from most consumer devices are
> not accurate.
>
> Whether you want to set up with 75% bars or 100% bars is up to you, and
> depends on what your bar generator will put out.
>
> Turn off any dynamic processing the monitor might have.
>
> Set the blacks:
>
> If you have PLUGE: Set the black level so the transition from the highest part
> of the PLUGE to the middle (reference blanking) is visible, but the transition
> from the middle one to the lower one is not discernable.
>
>
> Set chroma gain and phase:
>
> Looking through the filter, you should see 4 vertical bars. Look at the
> transition between the upper and lower bar (assuming you have split bars), and
> adjust the color gain and phase ("Color" and "Tint") until the black is
> uniform all up and down the black bars, the transitions should be invisible.
> The controls will interact somewhat.
>
>
> Setting the whites requires a photometer, but if all the above set up without
> problems you are close enough, especially if you know that the monitor was
> once set up correctly, with photometers etc.
>
> Who said analog was easy ?

Ah good point.  It hadn't occurred to me that he might be looking for
a tutorial on how to interpret the SMPTE bars.  I figured he was just
asking for what sort of nuance would be involved related to MythTV.

In terms of the your comments on the accuracy of the various formats,
I certainly agree.  However, I might argue that if the colors are
visibly off then even the color bars provided on DVD are probably good
enough.  It definitely won't give him studio quality, but would give
him something good enough for an untrained eye.

OTOH, I'm planning on playing with the default register programming
for the analog video decoders on some of the more popular tuners, and
you bet I wouldn't consider doing it if I didn't have a real pattern
generator.

Devin

-- 
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com